BIO 111 Unit 3: Genetic Biology - Cell Division (8) and DNA Structure and Replication (9)

Chapter 8: Cell Division - *Mitosis* *Please Please Make A Telephone Call* 1. Prophase: 2. Prometaphase: 3. Metaphase: 4. Anaphase: 5. Telophase 6. Cytokinesis:

1. chromosomes condense and become visible spindle fibers emerge from the centrosomes nuclear envelope breaks down nucleolus disappears 2. chromosomes continue to condense kinetochores appear at the centromeres mitotic spindle microtubules attach to kinetochores centrosomes move toward opposite poles 3. mitotic spindle is fully developed, centrosomes are at opposite poles of the cell chromosomes are lined up at the metaphase plate each sister chromatid is attached to a spindle fiber originating from opposite poles 4. cohesin proteins binding the sister chromatids together break down sister chromatids (now called chromosomes) are pulled toward opposite poles non-kinetochore spindle fibers lengthen, elongating the cell 5. chromosomes arrive at opposite poles and begin to decondenese nuclear envelope material surrounds each set of chromosomes the mitotic spindle breaks down 6. Animal cells: a cleavage furrow separates the daughter cells Plant cells: a cell plate separates the daughter cells

Chapter 8: Cell Division 1. genetic material of living organisms 2. Genes typically provide instructions for making ___________, which give cells and organisms their functional characteristics. 3. In bacteria and other prokaryotes, most of the DNA is found in a central region of the cell called the 4. Humans, for instance, have __#__ chromosomes in a typical body cell, while dogs have __#__ 5. the human chromosomes that determine a person's biological sex 6. The X and Y chromosomes are known as ___________, while the other 44 human chromosomes are called ___________ 7. In the first level of compaction, short stretches of the DNA double helix wrap around a core of eight histone proteins at regular intervals along the entire length of the chromosome. The DNA-histone complex is called ____________. The beadlike, histone DNA complex is called a ___________, and DNA connecting the nucleosomes is called ___________. (watch a video) 8. The next level of compaction occurs as the nucleosomes and the linker DNA between them are coiled into a 30-nm _____________. 9. In the third level of packing, a variety of _____________ is used to pack the chromatin. These also ensure that each chromosome in a non-dividing cell occupies a particular area of the nucleus that does not overlap with that of any other chromosome. 10. DNA replicates in the S phase of ____________. After replication, the chromosomes are composed of two linked sister __________. When fully compact, the pairs of identically packed chromosomes are bound to each other by ___________ proteins. The connection between the sister chromatids is closest in a region called the ____________.

1. DNA (deoxyribonucleic acid) - In humans, DNA is found in almost all the cells of the body and provides the instructions they need to grow, function, and respond to their environment 2. proteins 3. nucleoid - functions similarly to a nucleus but is not surrounded by a membrane 4. 46; 78 5. X and Y chromosomes 6. sex chromosomes; autosomes 7. chromatin; nucleosome; linker DNA - A DNA molecule in this form is about seven times shorter than the double helix without the histones, and the beads are about 10 nm in diameter, in contrast with the 2-nm diameter of a DNA double helix. 8. chromatin fiber - This coiling further shortens the chromosome so that it is now about 50 times shorter than the extended form 9. fibrous proteins 10. interphase; chromatids; cohesion; centromere - The conjoined sister chromatids, with a diameter of about 1 µm, are visible under a light microscope. The centromeric region is highly condensed and thus will appear as a constricted area.

Chapter 8: Cell Division 1. Proper chromosome duplication is assessed at the ________ checkpoint. 2. The M checkpoint occurs near the end of the ______ stage of karyokinesis. The M checkpoint is also known as the _________ checkpoint, because it determines whether all the sister chromatids are correctly attached to the spindle microtubules. Because the separation of the sister chromatids during ____________ is an irreversible step, the cycle will not proceed until the kinetochores of each pair of sister chromatids are firmly anchored to at least __#__ spindle fibers arising from opposite poles of the cell. 3. Cyclins regulate the cell cycle only when they are tightly bound to __________. To be fully active, the Cdk/cyclin complex must also be ___________ in specific locations. Like all kinases, Cdks are enzymes (kinases) that phosphorylate other proteins. Phosphorylation activates the protein by __________. The proteins phosphorylated by Cdks are involved in __________. The levels of Cdk proteins are relatively _________ throughout the cell cycle; however, the concentrations of ___________ fluctuate and determine when Cdk/cyclin complexes form. 4. If damaged DNA is detected, _________ halts the cell cycle and recruits enzymes to repair the DNA. If the DNA cannot be repaired, it can trigger _____________, or cell suicide, to prevent the duplication of damaged chromosomes 5. For the cell to move past each of the checkpoints, all _________ regulators must be "turned on," and all ______ regulators must be "turned off." 6. Proto-oncogenes are normal genes that, when mutated in certain ways, become __________, genes that cause a cell to become cancerous 7. any gene that, when altered, leads to an increase in the rate of cell cycle progression 8. Mutated p53 might lose its ability to trigger p21 production. Without adequate levels of p21, there is no effective block on _____________ activation. 9. Which checkpoint ensures sister chromatids are positioned to be split correctly? 10. The initiation signal for triggering cell division is ________

1. G1 2. metaphase; spindle; anaphase; two 3. Sdks; phosphorylated; changing its shape; advancing the cell to the next phase; stable; cyclin - The different cyclins and Cdks bind at specific points in the cell cycle and thus regulate different checkpoints. 4. p53; apoptosis 5. positive; negative 6. oncogenes 7. oncogene 8. Cdk 9. M checkpoint 10. an external event

Chapter 8: Cell Division - Meiosis I 1. Meiosis is preceded by an interphase consisting of the these 3 phases, which are nearly identical to the phases preceding mitosis. 2. The G1 phase, which is also called the first gap phase, is the first phase of the interphase and is focused on 3. during prophase I, the __________ complex, a lattice of proteins between the homologous chromosomes, first forms at specific locations and then spreads to cover the entire length of the chromosomes. The tight pairing of the homologous chromosomes is called _________ 4. (cont.) In synapsis, the _________ on the chromatids of the homologous chromosomes are aligned precisely with each other. The synaptonemal complex supports the exchange of chromosomal segments between non-sister homologous chromatids, a process called ____________. 5. As prophase I progresses, the synaptonemal complex begins to ___________ and the chromosomes begin to ___________. When the synaptonemal complex is gone, the homologous chromosomes remain attached to each other at the centromere and at ____________. 6. Following ___________, the synaptonemal complex breaks down and the cohesin connection between homologous pairs is also removed. At the end of prophase I, the pairs are held together only at the ____________ and are called ____________ because the four sister chromatids of each pair of homologous chromosomes are now visible. 7. The key event in ____________ is the attachment of the spindle fiber microtubules to the kinetochore proteins at the centromeres 8. during metaphase, there is a second form of genetic variation called 9. There are two possibilities for orientation at the metaphase plate; the possible number of alignments therefore equals _________, where n is the number of chromosomes per set. 10. In prometaphase I, microtubules attach to the fused kinetochores of ______________, and the homologous chromosomes are arranged at the midpoint of the cell in _____________. In anaphase I, the __________ are separated. In prometaphase II, microtubules attach to the kinetochores of ___________, and the sister chromatids are arranged at the midpoint of the cells in metaphase II. In anaphase II, the __________ are separated.

1. G1, S, and G2 2. cell growth 3. synaptonemal; synapsis 4. genes; crossing over; 5. break down; condense; chiasmata - The number of chiasmata varies according to the species and the length of the chromosome. 6. crossover; chiasmata; tetrads 7. prometaphase I 8. independent assortment 9. 2^n - Humans have 23 chromosome pairs, which results in over eight million (223) possible genetically-distinct gametes. - This number does not include the variability that was previously created in the sister chromatids by crossover. Given these two mechanisms, it is highly unlikely that any two haploid cells resulting from meiosis will have the same genetic composition 10. homologous chromosomes; metaphase I; homologous chromosomes; sister chromatids; sister chromatids

Chapter 8: Cell Division 1. The G1 checkpoint determines whether all conditions are favorable for __________ to proceed. The G1 checkpoint, also called the _________ point (in yeast), is a point at which the cell irreversibly commits to the cell division process. __________ influences, such as growth factors, play a large role in carrying the cell past the G1 checkpoint. In addition to adequate reserves and cell size, there is a check for _________ damage at the G1 checkpoint. A cell that does not meet all the requirements will not be allowed to progress into the S phase. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into ______ and await further signals when conditions improve. 2. there are two groups of intracellular molecules that regulate the cell cycle. These regulatory molecules either promote progress of the cell to the next phase (________ regulation) or halt the cycle (___________ regulation). Regulator molecules may act individually, or they can influence the activity or production of other regulatory proteins. Therefore, the failure of a single regulator may have (effect/no effect) on the cell cycle, especially if more than one mechanism controls the same event. 3. Since the cyclic fluctuations of cyclin levels are based on the _________ of the cell cycle and not on specific events, regulation of the cell cycle usually occurs by either the __________ molecules alone or the Cdk/cyclin complexes. 4. As p53 levels rise, the production of ________ is triggered. p21 enforces the halt in the cycle dictated by p53 by binding to and inhibiting the activity of the _____________. As a cell is exposed to more stress, (higher/lower) levels of p53 and p21 accumulate, making it less likely that the cell will move into the S phase. 5. Rb and other proteins that negatively regulate the cell cycle are sometimes called ____________. 6. If changes to the DNA nucleotide sequence occur within a coding portion of a gene and are not corrected, a gene ____________ results 7. the Cdk gene is considered a ___________ 8. ____________ are segments of DNA that code for negative regulator proteins, the type of regulators that, when activated, can prevent the cell from undergoing uncontrolled division 9. ___________ means that the offspring of any organism closely resemble their parent or parents. 10. a piece of DNA from one chromosome may get moved to another chromosome or to another region of the same chromosome; this is also known as

1. cell division; restriction; External; genomic DNA; G0 2. positive; negative; no effect - the effect of a deficient or non-functioning regulator can be wide-ranging and possibly fatal to the cell if multiple processes are affected. 3. timing; Cdk - Without a specific concentration of fully activated cyclin/Cdk complexes, the cell cycle cannot proceed through the checkpoints. 4. p21; Cdk/cyclin complexes; higher 5. tumor suppressors 6. mutation - Mutations can also be the result of the addition of a base, known as an insertion, or the removal of a base, also known as deletion 7. proto-oncogene 8. Tumor suppressor genes - A cell that carries a mutated form of a negative regulator might not be able to halt the cell cycle if there is a problem. 9. in kind - does not generally mean exactly the same. 10. translocation

Chapter 8: Cell Division 1. A pericentric inversion likely played a role in the evolutionary divergence of ________. 2. mechanism that ensures offspring are genetically different from parents and siblings. 3. A ________ is based on size, banding patterns, and centromere positions of chromosomes. 4. A(n) ________ individual has a change in the correct number of an individual chromosome. 5. a syndrome that results from an aneuploidy of an autosome 6. When a cell of the body divides, it will pass on a copy of its DNA to each of its 7. these two organelles contain their own DNA 8. Since all of the cells in an organism (with a few exceptions) contain the same DNA, you can also say that an organism has its own _________, and since the members of a species typically have similar genomes, you can also describe the genome of a _________ 9. Human sperm and eggs, which have only one homologous chromosome from each pair, are said to be __________. When a sperm and egg fuse, their genetic material combines to form one complete, diploid set of chromosomes 10. there is a gene found near the bottom of chromosome __#__ that affects eye color. A person might have the blue version, or ___________, of this gene on one homologue, but the brown version on the other. Both homologues have the same type of gene in the same place, but they can (and often do!) have different versions of genes.

1. chimpanzees and humans 2. crossing over within a homologous pair during meiosis 3. karyotype 4. aneuploid 5. 6. daughter cells - DNA is also passed on at the at the level of organisms, with the DNA in sperm and egg cells combining to form a new organism that has genetic material from both its parents. 7. mitochondria = mitochondrial DNA and chloroplast = chloroplast DNA - amounts of DNA are much smaller than the amount found in the nucleus 8. genome; species - when people refer to the human genome, or any other eukaryotic genome, they mean the set of DNA found in the nucleus (that is, the nuclear genome) - Mitochondria and chloroplasts are considered to have their own separate genomes. 9. haploid (1n) - half the number of chromosomes 10. 15; allele

Chapter 8: Cell Division - Meiosis I 1. In some organisms, the _________ decondense and ___________ form around the chromatids in telophase I. 2. In nearly all species of *animals and some fungi*, cytokinesis separates the cell contents via a ____________. In plants, a ___________ is formed during cell cytokinesis by Golgi vesicles fusing at the metaphase plate. 3. result of meiosis I 4. At which stage of meiosis are sister chromatids separated from each other? 5. The only source of variation in asexual organisms is 6. Nearly all *animals employ a diploid-dominant life-cycle* strategy in which the only haploid cells produced by the organism are the 7. The haploid multicellular plants are called ___________, because they produce gametes from specialized cells. Meiosis is not directly involved in the production of gametes in this case, because the organism that produces the gametes is already a ___________. 8. (cont.) Fertilization between the gametes forms a (haploid/diploid) zygote. The zygote will undergo many rounds of (mitosis/meiosis) and give rise to a diploid multicellular plant called a ___________. Specialized cells of the sporophyte will undergo (mitosis/meiosis) and produce haploid spores. The spores will subsequently develop into the __________ 9. Meiosis and fertilization create genetic variation by making new combinations of gene variants, or _________. In some cases, these new combinations may make an organism more or less fit, thus providing the raw material for _____________. 10. In *meiosis*, if the genes carried on two homologs are not oriented correctly, a recombination event could result in the loss of genes from one chromosome and the gain of genes on the other. This would produce __________ gametes.

1. chromosomes; nuclear envelopes 2. cleavage furrow; cell plate - constriction of the actin ring that leads to cytoplasmic division in animal cells 3. Two haploid cells - The cells are haploid because at each pole, there is just one of each pair of the homologous chromosomes. Therefore, only one full set of the chromosomes is present. 4. anaphase II 5. mutation 6. gametes - sperm and eggs 7 gametophytes; haploid 8. diploid; sporophyte; meiosis; gametophytes 9. alleles; natural selection - Genetic variation is important in allowing a population to adapt via natural selection and thus survive in the long term. 10. aneuploid

Chapter 8: Cell Division - Meiosis I 1. In other organisms, ___________—the physical separation of the cytoplasmic components into two daughter cells—occurs without reformation of the nuclei. 2. constriction of the actin ring that leads to cytoplasmic division 3. This cell plate from plant cells during cytokinesis will ultimately lead to the formation of __________ that separate the two daughter cells. 4. This is why the cells are considered (haploid/diploid)—there is only one chromosome set, even though each homolog still consists of two sister chromatids. 5. _____________ and meiosis alternate in sexual life cycles. 6. Early in the development of the embryo, specialized diploid cells, called _____________, are produced within the gonads, such as the testes and ovaries. 7. *in alteration of generations = plants*: The diploid plant is called a ____________ because it produces haploid spores by (mitosis/meiosis). The spores develop into multicellular, haploid plants called ____________ because they produce gametes. The gametes of two individuals will fuse to form a (haploid/diploid) zygote that becomes the _________ 8. the detachment, 180° rotation, and reinsertion of part of a chromosome. 9. a pericentric inversion in chromosome __________ appears to have contributed to the evolution of humans. This inversion is not present in our closest genetic relatives, the ___________. 10. A karyotype is the number and appearance of chromosomes, and includes their length, banding pattern, and centromere position. To obtain a view of an individual's karyotype, cytologists photograph the chromosomes and then cut and paste each chromosome into a chart, or __________, also known as an ideogram

1. cytokinesis 2. cleavage furrow 3. cell walls 4. haploid 5. Fertilization - Fertilization and meiosis alternate in sexual life cycles. What happens between these two events depends on the organism 6. germ cells - *gonads in males, ovaries in females* - product of mitosis (diploid cell, 2n) - it's special bc it can continue to do mitosis (produce 2 identical) or undergo meiosis (produce gametes - 4 cells w/ half # of chromosomes) 7. sporophyte; meiosis; gametophytes; diploid; sporophyte - Although all plants utilize some version of the alternation of generations, the relative size of the sporophyte and the gametophyte and the relationship between them vary 8. chromosome inversion - Inversions may occur in nature as a result of mechanical shear, or from the action of transposable elements (special DNA sequences capable of facilitating the rearrangement of chromosome segments with the help of enzymes that cut and paste DNA sequences) 9. 18; chimpanzees 10. karyotype; karyogram

Chapter 8: Cell Division - Meiosis I 1. Meiosis employs many of the same mechanisms as mitosis. However, the starting nucleus is always (haploid/diploid) and the nuclei that result at the end of a meiotic cell division are (haploid/diploid). To achieve this reduction in chromosome number, meiosis consists of one round of chromosome duplication and *two rounds of nuclear division*. 2. During DNA duplication in the S phase, each chromosome is replicated to produce __#__identical copies, called sister chromatids, that are held together at the centromere by cohesin proteins. 3. Early in prophase I, before the chromosomes can be seen clearly microscopically, the homologous chromosomes are attached at their tips to the ___________ by proteins. As the nuclear envelope begins to break down, the proteins associated with homologous chromosomes bring the pair (close to/far from) each other. 4. during prophase I: located at intervals along the synaptonemal complex are large protein assemblies called ______________. These assemblies mark the points of later chiasmata and mediate the multistep process of crossover—or _____________—between the non-sister chromatids 5. (cont.) Near the recombination nodule on each chromatid, the double-stranded DNA is ___________, the cut ends are modified, and a new connection is made between the non-sister chromatids. 6. There must be at least __#__ chiasma per chromosome for proper separation of homologous chromosomes during meiosis I, but there may be as many as 25. 7. The sister ____________ chromatid has a combination of maternal and paternal genes that did not exist before the crossover. 8. During ___________, the homologous chromosomes are arranged in the center of the cell with the kinetochores facing opposite poles. The homologous pairs orient themselves *randomly at the equator* 9. during metaphase I, the ___________ of homologous chromosomes at the metaphase plate—is the second mechanism that introduces variation into the gametes or spores. 10. in anaphase I, homologous pairs of chromosomes are pulled apart by ___________ attached to the kinetochore. The sister chromatids remain tightly bound together at the _____________. The ___________ are broken in anaphase I as the microtubules attached to the fused kinetochores pull the homologous chromosomes apart

1. diploid; haploid 2. two 3. nuclear envelope; close to; - Recall that, in mitosis, homologous chromosomes do not pair together. In mitosis, homologous chromosomes line up end-to-end so that when they divide, each daughter cell receives a sister chromatid from both members of the homologous pair. 4. recombination nodules; genetic recombination 5. cleaved 6. one 7. recombinant - Multiple crossovers in an arm of the chromosome have the same effect, exchanging segments of DNA to create recombinant chromosomes. 8. metaphase I - For example, if the two homologous members of chromosome 1 are labeled a and b, then the chromosomes could line up a-b, or b-a. This is important in determining the genes carried by a gamete, as each will only receive one of the two homologous chromosomes. Recall that homologous chromosomes are not identical. They contain slight differences in their genetic information, causing each gamete to have a unique genetic makeup. 9. random (or independent) assortment - In each cell that undergoes meiosis, the arrangement of the tetrads is different. The number of variations is dependent on the number of chromosomes making up a set. 10. microtubules; centromere; chiasmata

Chapter 8: Cell Division - Meiosis II 1. During meiosis II, the sister chromatids within the two daughter cells separate, forming __#__ new (haploid/diploid) gametes 2. in *prometaphse II*, the ___________ are completely broken down, and the __________ is fully formed. Each sister chromatid forms an individual ___________ that attaches to microtubules from opposite poles. 3. during anaphaseII, non-kinetochore microtubules __________ the cell. 4. how do sex cells form so that they each have only half of the genetic material that the resulting offspring will end up with? 5. These methods of reproduction do not require another organism of the opposite sex. 6. the multicellular haploid stage is the most obvious life stage, such as with all fungi and some algae 7. Most fungi and algae employ a life-cycle type in which the "body" of the organism—the ecologically important part of the life cycle—is haploid, which is called ___________ life cycle. The haploid cells that make up the tissues of the dominant multicellular stage are formed by __________. 8. When one homologous chromosome undergoes an inversion but the other does not, the individual is described as an inversion ___________. To maintain point-for-point synapsis during meiosis, one homolog must form a ____________, and the other homolog must mold around it. 9. ____________ translocations result from the exchange of chromosome segments between two nonhomologous chromosomes such that there is no gain or loss of genetic information 10. In a human karyotype, ___________ or "body chromosomes" (all of the non-sex chromosomes) are generally organized in approximate order of ________ from largest (chromosome 1) to smallest (chromosome 22)

1. four; haploid 2. nuclear envelopes; spindle; kinetochore 3. elongate 4. meiosis 5. asexual reproduction - In addition, in asexual populations, every individual is capable of reproduction. In sexual populations, the males are not producing the offspring themselves, so in theory an asexual population could grow twice as fast. 6. haploid-dominant 7. haploid-dominant; mitosis 8. heterozygote; loop - Although this topology can ensure that the genes are correctly aligned, it also forces the homologs to stretch and can be associated with regions of imprecise synapsis *When one chromosome undergoes an inversion but the other does not, one chromosome must form an inverted loop to retain point-for-point interaction during synapsis. This inversion pairing is essential to maintaining gene alignment during meiosis and to allow for recombination.* 9. Reciprocal 10. autosomes; size

Chapter 8: Cell Division 1. While the two X chromosomes in a woman's cells are genuinely _________, the X and Y chromosomes of a man's cells are not. They differ in size and shape, with the (X/Y) being much larger than the (X/Y), and contain mostly different genes 2. Double-stranded DNA wraps around histone proteins to form _________ that have the appearance of "beads on a string." The nucleosomes are coiled into a 30-nm ___________. When a cell undergoes _________, the chromosomes condense even further. 3. DNA is normally tightly packed into the nucleus of a eukaryotic cell, through ___________ complexes that form the characteristic condensed 'chromosome' shape 4. __________ are the first level of organization after DNA has wrapped around histones and looks like beads on a string 5. a fiber that is packed further by fibrous proteins 6. The first portion of the mitotic phase is called ______________, or nuclear division. The second portion of the mitotic phase, called _____________, is the physical separation of the cytoplasmic components into the two daughter cells. 7. During prophase, the "first phase," the nuclear envelope starts to dissociate into ___________, and the membranous organelles (such as the Golgi complex or Golgi apparatus, and endoplasmic reticulum), fragment and disperse toward the ___________ of the cell. The ____________ disappears (disperses). The centrosomes begin to move to opposite poles of the cell. ___________ that will form the mitotic spindle extend between the centrosomes, pushing them farther apart as the microtubule fibers lengthen. The ___________ begin to coil more tightly with the aid of condensin proteins and become visible under a light microscope. 8. During telophase, the "_____________ phase," the chromosomes reach the opposite poles and begin to ____________, relaxing into a chromatin configuration. The mitotic spindles are depolymerized into ____________ monomers that will be used to assemble cytoskeletal components for each daughter cell. _____________ form around the chromosomes, and ___________ appear within the nuclear area. 9. what happens during cytokinesis in animal cells? 10.

1. homologous; X; Y 2. nucleosomes; chromatin fiber; mitosis 3. protein-DNA 4. nucleosomes 5. chromatin 6. karyokinesis; cytokinesis 7. small vesicles; periphery; nucleolus; Microtubules; sister chromatids 8. distance; decondense (unravel); tubulin; Nuclear envelopes; nucleosomes 9. a cleavage furrow separates the daughter cells

Chapter 8: Cell Division - Meiosis II 1. In some species, cells enter a brief interphase, or _________, before entering meiosis II. Interkinesis lacks an ________ phase, so chromosomes are not duplicated. 2. The mechanics of meiosis II is similar to mitosis, except that each dividing cell has only one set of ____________. Therefore, each cell has half the number of sister chromatids to separate out as a ___________ cell undergoing mitosis. 3. during this phase, the sister chromatids are maximally condensed and aligned at the equator of the cell. 4. During telophase II, the chromosomes arrive at opposite poles and begin to ___________. _____________form around the chromosomes. Cytokinesis separates the two cells into __#__ unique haploid cells. At this point, the newly formed nuclei are both ____________. 5. An animal cell with a diploid number of four (2n = 4) proceeds through the stages of meiosis to form 6. sister chromatids are separated into single stranded chromosomes during 7. The process of meiosis reduces the chromosome number by ____________. Fertilization, the joining of two haploid gametes, restores the __________ condition 8. ________ cells are capable of mitosis to perpetuate the cell line and meiosis to produce gametes. Once the haploid gametes are formed, they lose the ability to __________ again. There is no multicellular haploid life stage. Fertilization occurs with the fusion of two gametes, usually from different individuals, restoring the ___________ state 9. Sexual reproduction takes many forms in multicellular organisms. However, at some point in each type of life cycle, (mitosis/meiosis) produces haploid cells that will fuse with the haploid cell of another organism. The mechanisms of ___________—crossover, random assortment of homologous chromosomes, and random fertilization—are present in all versions of sexual reproduction 10. Unless they disrupt a __________, inversions only change the orientation of genes and are likely to have more _________ effects than aneuploid errors. However, altered gene orientation can result in ___________ changes because regulators of gene expression could be moved out of position with respect to their targets, causing aberrant levels of gene products.

1. interkinesis; S 2. homologous chromosomes; diploid 3. metaphase II 4. decondense; Nuclear envelopes ; four; haploid - The cells produced are genetically unique because of the random assortment of paternal and maternal homologs and because of the recombining of maternal and paternal segments of chromosomes (with their sets of genes) that occurs during crossover. 5. four haploid daughter cells. 6. anaphase II 7. half; diploid 8. germ; divide; diploid 9. meiosis; variation - The fact that nearly every multicellular organism on Earth employs sexual reproduction is strong evidence for the benefits of producing offspring with unique gene combinations, though there are other possible benefits as well. 10. gene sequence; mild; functional

Chapter 8: Cell Division 1. During ___________, the cell undergoes normal growth processes while also preparing for cell division. In order for a cell to move into the mitotic phase, many internal and external conditions must be met. 2. The first stage of interphase is called the _________ (first gap) because, from a microscopic aspect, little change is visible. However, during the G1 stage, the cell is quite active at the biochemical level. The cell is accumulating the building blocks of __________ and the associated proteins as well as accumulating sufficient _____________ to complete the task of replicating each chromosome in the nucleus. 3. the S, phase is also known as the synthesis of ___________ phase. Throughout interphase, nuclear DNA remains in a semi-condensed ___________ configuration. In the S phase, DNA replication can proceed through the mechanisms that result in the formation of identical pairs of DNA molecules—sister ________—that are firmly attached to the centromeric region. The ___________ is duplicated during the S phase. The two centrosomes will give rise to the _____________, the apparatus that orchestrates the movement of chromosomes during mitosis. At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the __________, which are at right angles to each other. 4. in the _________ phase, the cell replenishes its energy stores and synthesizes proteins necessary for ___________. Some cell organelles are duplicated, and the __________ is dismantled to provide resources for the mitotic phase. There may be additional ____________ during G2. The final preparations for the ___________ phase must be completed before the cell is able to enter the first stage of mitosis. 5. first phase of mitosis 6. During metaphase, the "____________ phase," all the chromosomes are aligned in a plane called the ______________, or the ____________, midway between the two poles of the cell. The sister chromatids are still tightly attached to each other by __________ proteins. At this time, the chromosomes are maximally condensed. 7. _____________, or "cell motion," is the second main stage of the mitotic phase during which cell division is completed via the physical separation of the cytoplasmic components into two daughter cells. Division is not complete until the cell components have been apportioned and completely separated into the two daughter cells. Although the stages of mitosis are similar for most eukaryotes, the process of cytokinesis is quite different for eukaryotes that have ______________, such as plant cells. 8. In cells such as animal cells that lack cell walls, cytokinesis follows the onset of anaphase. A contractile ring composed of ____________ forms just inside the plasma membrane at the former ____________ plate. The actin filaments pull the equator of the cell inward, forming a fissure. This fissure, or "crack," is called the cleavage furrow. The furrow deepens as the actin ring contracts, and eventually the membrane is cleaved in two 9. In plant cells, a new ____________ must form between the daughter cells. During interphase, the _____________ accumulates enzymes, structural proteins, and glucose molecules prior to breaking into vesicles and dispersing throughout the dividing cell. During telophase, these Golgi vesicles are transported on microtubules to form a ______________ (a vesicular structure) at the metaphase plate. There, the vesicles fuse and coalesce from the center toward the cell walls; this structure is called a ____________. As more vesicles fuse, the cell plate enlarges until it merges with the cell walls at the periphery of the cell. Enzymes use the _________ that has accumulated between the membrane layers to build a new cell wall. The ________ membranes become parts of the plasma membrane on either side of the new cell wall 10. sex cells are (haploid/diploid)

1. interphase - The three stages of interphase are called G1, S, and G2. 2. G1 phase; chromosomal DNA; energy reserves 3. DNA; chromatin; chromatids; centrosome; mitotic spindle; centrioles 4. G2; chromosome manipulation; cytoskeleton; cell growth; mitotic 5. prophase 6. change; metaphase plate or equatorial plane; cohesin; 7. Cytokinesis; cell walls 8. actin filaments; metaphase; 9. cell wall; Golgi apparatus; phragmoplast; cell plate; glucose; Golgi 10. haploid

Chapter 8: Cell Division 1. The cell cycle has two major phases. During __________, the cell grows and DNA is replicated. During the __________ phase, the replicated DNA and cytoplasmic contents are separated, and the cell divides. 2. the apparatus that orchestrates the movement of chromosomes during mitosis 3. ____________ help organize cell division. They are not present in the centrosomes of other eukaryotic species, such as plants and most fungi but in humans they are. 4. Karyokinesis, also known as mitosis, is divided into a series of phases—prophase, prometaphase, metaphase, anaphase, and telophase—that results in 5. During pro metaphase, also called "______________", many processes that were begun in prophase continue to advance. The remnants of the nuclear envelope fragment. The mitotic spindle continues to develop as more __________ assemble and stretch across the length of the former nuclear area. Chromosomes become more condensed and discrete. Each sister chromatid develops a protein structure called a ______________ in the centromeric region 6. The proteins of the kinetochore attract and bind _____________. As the spindle microtubules extend from the centrosomes, some of these microtubules come into contact with and firmly bind to the kinetochores. Once a mitotic fiber attaches to a chromosome, the chromosome will be oriented until the kinetochores of sister chromatids face the (same/opposite) poles. 7. Eventually, all the sister chromatids will be attached via their _________ to microtubules from opposing poles. Spindle microtubules that do not engage the chromosomes are called __________ microtubules. These microtubules overlap each other midway between the two poles and contribute to __________. 8. ___________ microtubules are located near the poles, aid in spindle orientation, and are required for the regulation of mitosis. 9. what happens to plant cells during cytokinesis?

1. interphase; mitotic 2. mitotic spindle 3. centrioles 4. the division of the cell 5. first change phase; microtubules; kinetochore; 6. mitotic spindle microtubules; opposite; 7. kinetochores; polar; cell elongation 8. Astral 9. a cell plate separates the daughter cells

Chapter 8: Cell Division 1. In which stage of mitosis are the chromosomes are all aligned in the center of the cell? 2. Another factor that can initiate cell division is the size of the cell; as a cell grows, it becomes inefficient due to its decreasing __________ to ___________. The solution to this problem is to divide. 3. A _________ is one of several points in the eukaryotic cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable 4. Attachment of each kinetochore to a spindle fiber is assessed at the _______ checkpoint. 5. The G2 checkpoint bars entry into the __________ phase if certain conditions are not met. As at the G1 checkpoint, cell size and protein reserves are assessed. However, the most important role of the G2 checkpoint is to ensure that all of the ___________ have been replicated and that the replicated DNA is not damaged. If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA. 6. Two groups of proteins, called __________ and ___________, are responsible for the progress of the cell through the various checkpoints. The levels of the four cyclin proteins fluctuate throughout the cell cycle in a predictable pattern. Increases in the concentration of cyclin proteins are triggered by both external and internal signals. After the cell moves to the next stage of the cell cycle, the cyclins that were active in the previous stage are __________. 7. retinoblastoma protein (Rb), p53, and p21 are all ____________ and they act primarily at the G1 checkpoint 8. Rb exerts its regulatory influence on other _________ regulator proteins. Chiefly, Rb monitors _________. In the active, dephosphorylated state, Rb binds to proteins called ___________, most commonly, E2F. *Transcription factors "turn on" specific genes*, allowing the production of proteins encoded by that gene. When Rb is bound to E2F, production of proteins necessary for the ________ transition is blocked. As the cell increases in size, Rb is slowly phosphorylated until it becomes inactivated. Rb releases E2F, which can now turn on the gene that produces the transition protein, and this particular block is removed. 9. the pace of the cell cycle speeds up as the effectiveness of the control and repair mechanisms decreases. Uncontrolled growth of the mutated cells outpaces the growth of normal cells in the area, and a ___________ can result. 10. The genes that code for the positive cell cycle regulators are called

1. metaphase - during metaphase the push/pull of the mitotic spindle has balanced out with all chromosomes aligned at the cell's midline 2. surface-to-volume ratio 3. checkpoint - These checkpoints occur near the end of G1, at the G2/M transition, and during metaphase 4. M 5. mitotic; chromosomes; 6. cyclins and cyclin-dependent kinases (Sdks); degraded 7. negative regulatory molecules - halt the cell cycle - Retinoblastoma proteins are a group of tumor-suppressor proteins common in many cells. 8. positive; cell size; transcription factors; G1/S 9. tumor (~oma) 10. proto-oncogenes - A gene involved in normal cell growth. Mutations (changes) in a proto-oncogene may cause it to become an oncogene, which can cause the growth of cancer cells.

Chapter 8: Cell Division 1. disorders are caused by ___________, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. 2. if homologous chromosomes fail to separate during __________, the result is *two gametes that lack that particular chromosome and two gametes with two copies of the chromosome*. If sister chromatids fail to separate during __________, the result is *one gamete that lacks that chromosome, two normal gametes with one copy of the chromosome, and one gamete with two copies of the chromosome* 3. An individual with an error in chromosome number is described as _________, a term that includes ________ (loss of one chromosome) or _________ (gain of an extraneous chromosome). 4. ndividuals with this inherited disorder are characterized by short stature and stunted digits, facial distinctions that include a broad skull and large tongue, and significant developmental delays. 5. polyploidy is very common in the__________ kingdom, and polyploid plants tend to be larger and more robust than euploids of their species 6. X-chromosomal abnormalities are typically associated with mild _________ and physical defects, as well as __________. If the X chromosome is ________ altogether, the individual will not develop in utero. 7. __________, characterized as an *X0 genotype* (i.e., only a single sex chromosome), corresponds to a phenotypically female individual with *short stature, webbed skin in the neck region, hearing and cardiac impairments, and sterility*.

1. nondisjunction 2. meiosis I; meiosis II 3. aneuploid; monosomy; trisomy 4. trisomy 21, down syndrome - The incidence of Down syndrome is correlated with maternal age; older women are more likely to become pregnant with fetuses carrying the trisomy 21 genotype 5. plant 6. mental; sterility; absent 7. Turner syndrome

Chapter 8: Cell Division 1. In eukaryotes such as plants and animals, the great majority of DNA is found in the nucleus and is called _________ DNA 2. A cell's set of DNA is called its _________ 3. humans are __________, meaning that most of their chromosomes come in matched sets known as homologous pairs. Thus, the 46 chromosomes of a human cell are organized into ________ pairs, and the two members of each pair are said to be homologues of one another (with the slight exception of the X and Y chromosomes) 4. two chromosomes in a homologous pair are generally very similar to one another. They're the same size and shape, and have the same pattern of light and dark bands. Bands appear when the chromosomes are stained with a dye, and the dark bands mark more compacted DNA, usually with (more/fewer) genes, while the light bands mark less compacted DNA, usually with (more/fewer) genes. Most importantly, the two homologues in a pair carry (similar/different) type of genetic information 5. sex chromosomes for females? for males? 6. describe the organization of eukaryotic chromosomal DNA 7. Pairs of chromosomes, also known as ___________, contain the same genes though there may be differences between the version (allele) of gene on each member of the pair. 8. A ________ is formed from beadlike histone-DNA complexes. 9. Fibrous proteins pack ________ nucleosomes chromatin once it is formed to ensure ___________chromatin chromosomes do(es) not overlap in the nucleus during cell division. 10. the most compacted forms of DNA; they cannot overlap in the nucleus during division or else errors in DNA segregation may occur

1. nuclear 2. genome 3. diploid (2n); 23 - for each homologous pair of chromosomes in your genome, one of the homologues comes from your mom and the other from your dad. 4. fewer; more; similar/the same 5. XX = female; XY = male 6. Chromatin > Chromatin fibers > Proteins pack fibers 7. homologous chromosomes 8. nucleosome 9. chromatin; chromosomes 10. chromosomes

Chapter 9: DNA Structure & Replication 1. The building blocks of DNA are ___________. each is named depending on its ___________ 2. In the 1950s, Francis Crick and James Watson worked together to determine the _____________ at the University of Cambridge, England 3. The ____________ of the nucleotides form the backbone of the DNA structure, whereas the nitrogenous bases are stacked inside. 4. Most prokaryotes contain a single, ___________ chromosome that is found in an area of the cytoplasm called the nucleoid. 5. In *interphase, eukaryotic chromosomes* have two distinct regions that can be distinguished by staining. The *tightly packaged* region is known as ___________, and the *less dense* region is known as __________. Heterochromatin usually contains genes that (are/are not) expressed, and is found in the regions of the *centromere and telomeres*. The euchromatin usually contains genes that (are/are not) transcribed, with DNA packaged *around nucleosomes* but not further compacted. 6. Griffith's experiment with mice proved bacterial ____________ 7. Avery, MacLeod, and McCarty proved that DNA is required for the _____________ of bacteria. 8. In __________ replication, the parental DNA remains together, and the newly formed daughter strands are together. 9. The process of DNA replication is catalyzed by a type of enzyme called ____________ 10. The synthesis of the new DNA strand can only happen in one direction: from the ________ to _________

1. nucleotides; nitrogenous base. - nitrogenous base, deoxyribose (5-carbon sugar), and a phosphate group 2. structure of DNA - really Rosalind Franklin! 3. sugar and phosphate (sides of ladder) - bases = rungs of ladder 4. circular 5. heterochromatin; euchromatin; are not; are 6. transformation - concluded that something had passed from the heat-killed S strain into the live R strain and transformed it into the pathogenic S strain, and he called this the transforming principle 7. transformation 8. conservative 9. DNA polymerase 10. 5′ to the 3′ end - In other words, the *new bases are always added to the 3′ end* of the newly synthesized DNA strand.

Chapter 9: DNA Structure & Replication 1. DNA polymerase only works in one direction along the strand (5′ to 3′), but the double-stranded DNA has two strands oriented in opposite directions. This problem is solved by synthesizing the two strands slightly differently: 2. Synthesizes the new DNA strand; also proofreads and corrects some errors 3. Some errors are not corrected during replication, but are instead *corrected after replication is completed*; this type of repair is known as _____________ 4. The ends of the linear chromosomes are known as _______________, which have repetitive sequences that code for no particular gene. 5. The ends of the chromosomes pose a problem during DNA replication as polymerase is unable to extend them without a _____________. Telomerase, an enzyme with a built-in RNA template, extends the ends by copying the RNA template and extending one end of the chromosome. DNA polymerase can then extend the DNA using the primer. In this way, the ends of the chromosomes are protected. 6. a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke. 7. ____________ mutations occur at some time during a person's life and are present only in certain cells, not in every cell in the body. 8. Genetic alterations that occur in more than 1 percent of the population are called ___________. 9. Mutations may have a wide range of effects. Some mutations are not expressed; these are known as __________ mutations. ___________ mutations are those mutations that affect a single base pair. The most common nucleotide mutations are substitutions, in which one base is replaced by another. These can be of two types, either transitions or transversions. 10. Mutations in __________ genes have been known to cause cancer

1. one new strand grows continuously, the other in bits and pieces. Short fragments of RNA are used as primers for the DNA polymerase 2. DNA polymerase - proofreading, the DNA pol reads the newly added base before adding the next one, so a correction can be made. If an *incorrect base has been added, the enzyme makes a cut at the phosphodiester bond* and releases the wrong nucleotide. 3. mismatch repair - The enzymes recognize the incorrectly added nucleotide and excise it; this is then replaced by the correct base. If this remains uncorrected, it may lead to more permanent damage. 4. telomeres 5. primer 6. mutation 7. Acquired (or somatic) - These changes can be caused by environmental factors such as ultraviolet radiation from the sun, or can occur if a mistake is made as DNA copies itself during cell division 8. polymorphisms - responsible for many of the normal differences between people such as eye color, hair color, and blood type. Although many polymorphisms have no negative effects on a person's health, some of these variations may influence the risk of developing certain disorders. 9. silent; point 10. repair

Chapter 8: Cell Division 1. *karyotypes*: The chromosome "arms" projecting from either end of the centromere may be designated as short or long, depending on their relative lengths. The short arm is abbreviated ________, whereas the long arm is abbreviated ___________ 2. Nondisjunction can occur during either __________ or ___________, with differing results 3. An individual with the appropriate number of chromosomes for their species is called 4. (Monosomic/Trisomic) individuals suffer from a different type of genetic imbalance: an *excess* in gene dose. Individuals with an extra chromosome may synthesize an abundance of the gene products encoded by that chromosome. This extra dose (150 percent) of specific genes can lead to a number of functional challenges and often precludes development. 5. Polyploid animals are __________ because meiosis cannot proceed normally and instead produces mostly aneuploid daughter cells that cannot yield viable zygotes. 6. *X inactivation*: Early in development, when female mammalian embryos consist of just a few thousand cells (relative to trillions in the newborn), one X chromosome in each cell inactivates by tightly condensing into a quiescent (dormant) structure called a ___________. The chance that an X chromosome (maternally or paternally derived) is inactivated in each cell is ___________, but once the inactivation occurs, all cells derived from that one will have the same inactive X chromosome or Barr body. By this process, females compensate for their double genetic dose of X chromosome. 7. The __________ genotype, corresponding to one type of *Klinefelter syndrome*, corresponds to phenotypically *male individuals with small testes, enlarged breasts, and reduced body hair*. 8. ___________ is a syndrome associated with nervous system abnormalities and identifiable physical features that result from a *deletion of most of 5p* (the small arm of chromosome 5)

1. p (for "petite"); q (because it follows "p" alphabetically) - Each arm is further subdivided and denoted by a number. Using this naming system, locations on chromosomes can be described consistently in the scientific literature. 2. meiosis I or II 3. euploid - in humans, euploidy corresponds to 22 pairs of autosomes and one pair of sex chromosomes. 4. Trisomic 5. sterile - Rarely, polyploid animals can reproduce asexually by haplodiploidy, in which an unfertilized egg divides mitotically to produce offspring. 6. Barr body; random 7. XXY - More complex types of Klinefelter syndrome exist in which the individual has as many as five X chromosomes. In all types, every X chromosome except one undergoes inactivation to compensate for the excess genetic dosage. This can be seen as several Barr bodies in each cell nucleus 8. Cri-du-chat (from the French for "cry of the cat");

Chapter 8: Cell Division - Meiosis I 1. Mutated _________ genes have been identified in more than one-half of all human tumor cells. This discovery is not surprising in light of the multiple roles that the p53 protein plays at the G1 checkpoint. 2. ______________ is the part of a cell reproduction cycle that results in *identical daughter nuclei that are also genetically identical to the original parent nucleus*. both the parent and the daughter nuclei are at the same ploidy level—diploid for most plants and animals 3. The S phase is the second phase of interphase, during which the DNA of the chromosomes is 4. crossing over occurs during 5. Early in prophase I, homologous chromosomes come together to form a _____________. The chromosomes are bound tightly together and in perfect alignment by a protein lattice called a ________________ and by cohesin proteins at the ______________. 6. The chiasmata remain from prophase I until 7. Crossover occurs between non-sister chromatids of ____________ chromosomes. The result is an exchange of genetic material between homologous chromosomes. 8. Kinetochore proteins are multiprotein complexes that bind the _____________ of a chromosome to the _____________ of the mitotic spindle. Microtubules grow from ____________ placed at opposite poles of the cell. The microtubules move toward the middle of the cell and attach to one of the two fused homologous chromosomes and attach at each chromosomes' _____________ 9. (cont.) With each member of the homologous pair attached to opposite poles of the cell, in the next phase, the _____________ can pull the homologous pair apart. A spindle fiber that has attached to a kinetochore is called a _______________. 10. independent assortment occurs during

1. p53 - A cell with a faulty p53 may fail to detect errors present in the genomic DNA 2. mitosis 3. replicated 4. prophase I - If meiosis happens many times, as it does in human ovaries and testes, crossovers will happen at many different points. 5. synapse; synaptonemal complex; centromere 6. anaphase I 7. homologous 8.centromeres; microtubules; centrosomes; kinetochores 9. microtubules; kinetochore microtubule 10. metaphase I

Chapter 9: DNA Structure & Replication 1. nucleotides combine with each other by covalent bonds known as ___________ 2. base pairs are stabilized by __________ bonds 3. In order for DNA to function effectively at storing information, two key processes are required. First, information stored in the DNA molecule must be _________, with minimal errors, every time a cell divides. This ensures that both daughter cells inherit the complete set of genetic information from the parent cell. Second, the information stored in the DNA molecule must be ___________, or expressed. In order for the stored information to be useful, cells must be able to access the instructions for making specific proteins, so the correct proteins are made in the right place at the right time. 4. *in eukaryotes:* At the most basic level, DNA is wrapped around proteins known as ___________ to form structures called _____________. The histones are evolutionarily conserved proteins that are rich in basic amino acids and form an octamer. The DNA (which is negatively charged because of the phosphate groups) is wrapped tightly around the histone core. This nucleosome is linked to the next one with the help of a linker DNA. This is also known as the "___________" structure. This is further compacted into a 30 nm __________, which is the diameter of the structure. At the ___________ stage, the chromosomes are at their most compact, are approximately 700 nm in width, and are found in association with scaffold proteins. 5. DNA was first isolated from white blood cells by Friedrich Miescher, who called it _____________ because it was isolated from nuclei. 6. The ___________ method suggests that each of the two parental DNA strands act as a template for new DNA to be synthesized; after replication, each double-stranded DNA includes one parental or "old" strand and one "new" strand. 7. The two strands of DNA have to be temporarily separated from each other; this job is done by a special enzyme, ___________, that helps unwind and separate the DNA helices 8. enzyme that re-joins the two DNA strands into a double helix and joins Okazaki fragments of the lagging strand 9. during proofreading by DNA polymerase, an incorrect nucleotides is removed by the *exonuclease action* of __________. Once the incorrect nucleotide has been removed, a new one will be added again. 10. This repair mechanism is often employed *when UV exposure causes the formation of pyrimidine dimers.*

1. phosphodiester bonds or linkages 2. hydrogen - adenine and thymine form two hydrogen bonds and cytosine and guanine form three hydrogen bonds. - The two strands are anti-parallel in nature; that is, the 3′ end of one strand faces the 5′ end of the other strand 3. copied; translated 4. histones; nucleosomes; beads on a string; fiber; metaphase 5. nuclein 6. semi-conservative - Experimental evidence showed *DNA replication is semi-conservative.* 7. helicase 8. DNA ligase 9. DNA pol III 10. nucleotide excision repair

Chapter 9: DNA Structure & Replication 1. adenine (A) and guanine (G) are ___________ while cytosine (C), thymine (T), and uracil (U) - in RNA are __________ 2. The information stored in the order of bases is organized into ___________: each gene contains information for making a functional product. genetic information is first copied to another nucleic acid polymer called ___________, preserving the order of the nucleotide bases. Genes that contain instructions for making proteins are converted to ___________. 3. The sequence of the bases codes for the instructions for _____________. 4. *in prokaryotes*, DNA is twisted by what is known as ___________. this means that DNA is either under-wound (less than one turn of the helix per 10 base pairs) or over-wound (more than 1 turn per 10 base pairs) from its normal relaxed state. Some proteins are known to be involved in this process; other proteins and enzymes such as ___________ help in maintaining the supercoiled structure. 5. Information stored in DNA must be ________ into specific functional products. 6. In eukaryotic cells, the ________ region of DNA is usually expressed, while the ________ region is not. 7. Chase and Hershey were studying a bacteriophage and concluded 8. ___________ is the scientist who found that the ratio of *A = T and C = G*, and that the percentage content of A, T, G, and C is different for different species. 9. In the __________ model, both copies of DNA have double-stranded segments of parental DNA and newly synthesized DNA interspersed. 10. DNA polymerase needs an "anchor" to start adding nucleotides: a *short sequence of DNA or RNA that is complementary to the template strand* will work to provide a free 3′ end. This sequence is called a ___________

1. purine, pyrimidines - Purines have a double ring structure with a six-membered ring fused to a five-membered ring. Pyrimidines are smaller in size; they have a single six-membered ring structure. - Base pairing takes place between a purine and pyrimidine; 2. genes; RNA (ribonucleic acid); messenger RNA (mRNA) - These RNA molecules function by affecting cellular processes directly; for example some of these RNA molecules regulate the expression of mRNA. Other genes produce RNA molecules that are required for protein synthesis, transfer RNA (tRNA), and ribosomal RNA (rRNA). 3. protein synthesis 4. supercoiling;DNA gyrase 5. translated 6. euchromatin; heterochromatin 7. Hershey and Chase concluded that it was the phage DNA that was injected into the cell and carried information to produce more phage particles, thus providing evidence that *DNA was the genetic material and not proteins* 8. Chargaff 9. dispersive 10. primer

Chapter 8: Cell Division - Meiosis I 1. (A/Sexual) reproduction, specifically meiosis and fertilization, introduces variation into offspring that may account for the evolutionary success of sexual reproduction. The vast majority of eukaryotic organisms, both multicellular and unicellular, can or must employ some form of meiosis and fertilization to reproduce. 2. the G2 phase, also called the second gap phase, is the third and final phase of interphase; in this phase, the cell undergoes the 3. During DNA duplication in the S phase, each chromosome is replicated to produce __#__ identical copies, called sister chromatids, that are held together at the centromere by __________ proteins, which hold the sister chromatids together until ____________ 4. (cont.) The ___________, which are the structures that organize the microtubules of the meiotic spindle, also replicate. This prepares the cell to enter ____________, the first meiotic phase. 5. Crossing over can be observed visually after the exchange as ________ 6. n species such as humans, even though the X and Y sex chromosomes are not ____________ (most of their genes differ), they have a small region of homology that allows the X and Y chromosomes to pair up during _____________. A partial synaptonemal complex develops only between the regions of homology. 7. The crossover events are the first source of genetic variation in the ___________ produced by meiosis. A single crossover event between homologous non-sister chromatids leads to a reciprocal exchange of equivalent DNA between a maternal chromosome and a paternal chromosome. Now, when that sister chromatid is moved into a ____________ cell it will carry some DNA from one parent of the individual and some DNA from the other parent. 8. At the end of prometaphase I, each tetrad is attached to _____________ from both poles, with one homologous chromosome facing each _________. The homologous chromosomes are still held together at ____________. In addition, the ___________ has broken down entirely. 9. In metaphase I, these homologous chromosome pairs line up at the midway point between the two poles of the cell to form the _____________. Because there is an equal chance that a microtubule fiber will encounter a maternally or paternally inherited chromosome, the arrangement of the tetrads at the metaphase plate is ___________. 10. to summarize the genetic consequences of meiosis I, the maternal and paternal genes are recombined by ____________ events that occur between each homologous pair during prophase I. In addition, the random assortment of ____________ on the metaphase plate produces a unique combination of maternal and paternal chromosomes that will make their way into the gametes.

1. sexual 2. final preparations for meiosis. 3. two; cohesin; anaphase II 4. centrosomes; prophase I - an organelle near the nucleus of a cell which contains the centrioles (in animal cells) and from which the spindle fibers develop in cell division. 5. chiasmata (singular = chiasma) 6. homologous; prophase I 7. nuclei; gamete 8. microtubules; pole; chiasmata; nuclear membrane 9. metaphase plate; random - Any maternally inherited chromosome may face either pole. Any paternally inherited chromosome may also face either pole. The orientation of each tetrad is independent of the orientation of the other 22 tetrads. 10. crossover; tetrads

Chapter 8: Cell Division 1. The X and Y chromosomes are not autosomes. However, chromosome 21 is actually ________ than chromosome 22. This was discovered after the naming of the disease __________ as trisomy 21, reflecting how this disease results from possessing one extra chromosome 21 (three total). 2. Misaligned or incomplete synapsis, or a dysfunction of the spindle apparatus that facilitates chromosome migration, can cause ___________. the risk of this happening increases with 3. __________ occurs when homologous chromosomes or sister chromatids fail to separate during meiosis, resulting in an abnormal chromosome number. 4. (Monosomic/Trisomic) human zygotes missing any one copy of an autosome invariably fail to develop to birth because they lack essential genes. 5. An individual with more than the correct number of chromosome sets (two for diploid species) is called 6. for humans, variations in the number of sex chromosomes are associated with relatively mild effects. In part, this occurs because of a molecular process called __________. 7. Several errors in sex chromosome number have been characterized. Individuals with three X chromosomes, called __________, are phenotypically female but express __________ and _________ 8. Duplications and deletions often produce offspring that survive but exhibit __________ and _________ abnormalities.

1. shorter; Down syndrome 2. nondisjunction; the age of the parents 3. Nondisjunction 4. Monosomic - Most autosomal trisomies also fail to develop to birth; however, *duplications of some of the smaller chromosomes (13, 15, 18, 21, or 22) can result in offspring that survive* for several weeks to many years 5. polyploid - Polyploid animals are extremely rare, with only a few examples among the flatworms, crustaceans, amphibians, fish, and lizards. 6. X inactivation 7. triplo-X; developmental delays and reduced fertility. 8. physical and mental - Duplicated chromosomal segments may fuse to existing chromosomes or may be free in the nucleus.

Chapter 8: Cell Division - Meiosis II 1. The two cells produced in meiosis I go through the events of meiosis II in ___________. 2. In *prophase II*, if the chromosomes decondensed in telophase I, they __________ again. If nuclear envelopes were formed, they fragment into __________. The ___________ that were duplicated during interkinesis move away from each other toward opposite poles, and new spindles are formed. 3. The sister chromatids are pulled apart by the kinetochore microtubules and move toward opposite poles. 4. One of the most important results of ________ is genetically unique cells. 5. the multicellular diploid stage is the most obvious life stage, such as with most animals including humans 6. In animals, sexually reproducing adults form (haploid/diploid) gametes from diploid ___________ cells. Fusion of the gametes gives rise to a fertilized egg cell, or _________. The zygote will undergo multiple rounds of ___________ to produce a multicellular offspring. The _________ are generated early in the development of the zygote. 7. The process of *meiosis* produces unique reproductive cells called ___________, which have half the number of chromosomes as the parent cell. Fertilization, the fusion of haploid gametes from two individuals, restores the _________ condition. 8. An *inversion* can be two things: ______________ inversions include the centromere, and _____________ inversions do not. A ___________ inversion can change the relative lengths of the chromosome arms; a paracentric inversion cannot. 9. A _____________ occurs when a segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome. specific translocations have been associated with several cancers and with ____________. 10. fertilized egg

1. synchrony 2. condense; vesicles; centrosomes 3. anaphase II 4. meiosis 5. diploid-dominant 6. haploid; germ; zygote; mitosis; germ cells 7. gametes; diploid - Thus, sexually reproducing organisms alternate between haploid and diploid stages. 8. pericentric; paracentric; pericentric - A *pericentric inversion* that is asymmetric about the centromere can change the relative lengths of the chromosome arms, making these inversions easily identifiable. 9. translocation; schizophrenia - Translocations can be benign or have devastating effects depending on how the positions of genes are altered with respect to regulatory sequences. 10. zygote

Chapter 8: Cell Division - Meiosis I 1. In ____________, the separated chromosomes arrive at opposite poles. The remainder of the typical events in this step may or may not occur, depending on the species. 2. formed during cell cytokinesis by Golgi vesicles fusing at the metaphase plate. 3. __#__ (haploid/diploid) cells are the end result of the first meiotic division 4. result of meiosis II 5. The part of meiosis that is similar to mitosis is ________. 6. Why is sexuality (and meiosis) so common? 7. the two life cycles (fertilization and meiosis) are apparent to different degrees depending on the group, as with plants and some algae. 8. For *haploid-dominant life cycle:* During sexual reproduction, specialized haploid cells from two individuals, designated the ________ and __________ mating types, join to form a (haploid/diploid) zygote. The zygote immediately undergoes ___________ to form four haploid cells called spores. 9. (cont.) Although (haploid/diploid) like the "parents," these spores contain a new genetic combination from two parents. The spores can remain _________ for various time periods. Eventually, when conditions are conducive, the spores form multicellular haploid structures by many rounds of _________ 10. Random orientation of homologue pairs occurs during ___________ of meiosis I

1. telophase I 2. cell plate 3. Two haploid 4. In meiosis II, the two sister chromatids will separate, creating *four haploid daughter cells*. 5. meiosis II 6. one of which is that the variation that sexual reproduction creates among offspring is very important to the survival and reproduction of the population. - a sexually reproducing population will leave more descendants than an otherwise similar asexually reproducing population 7. alteration of generations 8. (+) and (−); diploid; meiosis 9. haploid; dormant; mitosis 10. metaphase I - During meiosis I, the homologous pairs will separate to form two equal groups, but it's not usually the case that all the paternal chromosomes will go into one group and all the maternal chromosomes into the other.

Chapter 9: DNA Structure & Replication 1. During DNA replication, what is later replaced with DNA bases? 2. enzyme that provides the starting point for DNA polymerase to begin synthesis of the new strand 3. in this type of repair mechanism, enzymes replace incorrect bases by making a cut on both the 3′ and 5′ ends of the incorrect base 4. The ends of linear chromosomes are maintained by the action of the _____________ enzyme. 5. sickle cell anemia is caused by a mutation that instructs the building of a protein called hemoglobin. However, in African populations, having this mutation also protects against __________. 6. ____________ mutations in somatic cells (cells other than sperm and egg cells) cannot be passed on to the next generation. 7. Affected individuals have skin that is highly sensitive to UV rays from the sun. 8. _____________ substitution refers to a purine or pyrimidine being replaced by a base of the same kind. ____________ substitution refers to a purine being replaced by a pyrimidine, or vice versa 9. insertion and deletion can both lead to _____________ mutations 10. two genes on the same chromosome switch places

1. the RNA primer is replaced with DNA nucleotides 2. primase 3. nucleotide excision repair - The segment of DNA is removed and replaced with the correctly paired nucleotides by the action of DNA pol. Once the bases are filled in, the remaining gap is sealed with a phosphodiester linkage catalyzed by DNA ligase. 4. telomerase - telomerase is typically active in germ cells and adult stem cells. It is not active in adult somatic cells. 5. malaria 6. Acquired - Genetic changes that are described as d*e novo (new) mutations* can be either hereditary or somatic 7. xeroderma pigmentosa - These are not repaired because of a defect in the nucleotide excision repair enzymes, whereas in normal individuals, the thymine dimers are excised and the defect is corrected. The thymine dimers distort the structure of the DNA double helix, and this may cause problems during DNA replication. People with xeroderma pigmentosa may have a higher risk of contracting skin cancer than those who don't have the condition. 8. Transition; Transversion - for example, a purine such as adenine may be replaced by the purine guanine 9. frameshift 10. chromosomal mutation

Chapter 9: DNA Structure & Replication 1. enzyme that relaxes the super-coiled DNA 2. enzyme that unwinds the double helix at the replication fork 3. Cells that undergo cell division continue to have their telomeres shortened because most somatic cells do not make telomerase. This essentially means that telomere shortening is associated with ___________ 4. cancer cells accumulate mutations, proliferate uncontrollably, and can migrate to different parts of the body through a process called 5. ____________ mutations are inherited from a parent and are present throughout a person's life in virtually every cell in the body. These mutations are also called ___________ mutations because they are present in the parent's egg or sperm cells, which are also called germ cells. 6. Somatic mutations that happen in a single cell early in embryonic development can lead to a situation called ___________ - These genetic changes are not present in a parent's egg or sperm cells, or in the fertilized egg, but happen a bit later when the embryo includes several cells. 7. ___________ mutations are those that result from an exposure to chemicals, UV rays, x-rays, or some other environmental agent. _____________ mutations occur without any exposure to any environmental agent; they are a result of natural reactions taking place within the body

1. topoisomerase 2. DNA helicase 3. aging - With the advent of modern medicine, preventative health care, and healthier lifestyles, the human life span has increased, and there is an increasing demand for people to look younger and have a better quality of life as they grow older. 4. metastasis - Scientists have observed that cancerous cells have considerably shortened telomeres and that telomerase is active in these cells. Interestingly, only after the telomeres were shortened in the cancer cells did the telomerase become active. If the action of telomerase in these cells can be inhibited by drugs during cancer therapy, then the cancerous cells could potentially be stopped from further division. 5. Hereditary; germline - When an egg and a sperm cell unite, the resulting fertilized egg cell receives DNA from both parents. If this DNA has a mutation, the child that grows from the fertilized egg will have the mutation in each of his or her cells. 6. mosaicism - As all the cells divide during growth and development, cells that arise from the cell with the altered gene will have the mutation, while other cells will not. Depending on the mutation and how many cells are affected, mosaicism may or may not cause health problems. 7. Induced; Spontaneous

Chapter 8: Cell Division 1. what does mitosis produce? 2. during anaphase, the "___________ phase," the cohesin proteins degrade, and the sister chromatids separate at the __________. Each chromatid, now called a ____________, is pulled rapidly toward the centrosome to which its microtubule is attached. The cell becomes visibly elongated (oval shaped) as the ___________ microtubules slide against each other at the metaphase plate where they overlap. 3. what are haploid cells? 4. cells spend the most time in this phase 5. chromosomes are duplicated during what portion of the cell cycle? 6. ________ is the first stage of mitosis in which the nuclear envelope disassembles. 7. When fast-dividing mammalian cells are grown in culture (outside the body under optimal growing conditions), the length of the cycle is about ___________. 8. Both the initiation and inhibition of cell division are triggered by events (internal/external) to the cell when it is about to begin the replication process. 9. The cell cycle is controlled at three checkpoints. The integrity of the DNA is assessed at the ___________ checkpoint. 10. Molecules that prevent the full activation of Cdks are called ____________. Many of these inhibitor molecules directly or indirectly monitor a particular cell cycle event. The block placed on Cdks by inhibitor molecules will not be removed until the specific event that the inhibitor monitors is completed.

1. two new, identical daughter cells - The mitotic phase (also known as M phase) is a multistep process during which the duplicated chromosomes are aligned, separated, and move into two new, identical daughter cells. 2. upward; centromere; chromosome; polar; 3. cells that are half as many as diploid 4. interphase 5. S phase 6. prophase 7. 24 hours - In rapidly dividing human cells with a 24-hour cell cycle, the G1 phase lasts approximately nine hours, the S phase lasts 10 hours, the G2 phase lasts about four and one-half hours, and the M phase lasts approximately one-half hour. 8. external 9. G1 10. Cdk inhibitors - Molecules that prevent the full activation of Cdks are called Cdk inhibitors. Many of these inhibitor molecules directly or indirectly monitor a particular cell cycle event. The block placed on Cdks by inhibitor molecules will not be removed until the specific event that the inhibitor monitors is completed.

Chapter 8: Cell Division 1. During G2 phase, the cell: 2. in which stage of mitosis are the chromosomes all aligned in the center of the cell? 3. the structures that gives rise to the cell plate in plant cells is called 4. What is the main prerequisite for clearance at the G2 checkpoint? 5. In order for cancer to develop, a ________ would need to be inactivated. 6. Even though the processes are very similar, mitosis and meiosis are two very distinct processes. What is the difference between meiosis and mitosis? 7. the end products of meiosis I are _#__ (haploid/diploid) cells 8. One of the most important results of (mitosis/meiosis) is genetically unique cells. 9. Scientists believe ________ is common in organisms because it increases genetic variation. 10. Recombinant chromosomes contain ________

1. undergoes final preparation for cell division 2. metaphase 3. phragmoplast 4. accurate and complete DNA replication 5. tumor suppressor 6. 7. two haploid cells 8. meiosis 9. sexual reproduction 10.