Biology Exam 3 : Ch. 12-15

meiosis telophase 1

nuclear membrane forms around each new nucleus, at this point each chromosome still consists of sister chromatids joined by centromere

bivalent

paired homologous chromosomes

polymorphic trait

a trait that appears commonly in two or more different forms

lagging strand

A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.

cell plate

A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.

Dynein

A large contractile protein forming the side-arms of microtubule doublets in cilia and flagella.

After the formation of a replication bubble, which of the following is the correct sequence for synthesis of the lagging DNA strand? 1. Helicase breaks hydrogen bonds between base pairs to open the DNA helix. 2. Ligases seal gaps in the sugar-phosphate backbone. 3. Polymerase I removes the RNA primer and replaces it with DNA. 4. Primase adds the RNA primers to new DNA strand 5. Polymerase III adds DNA nucleotides to synthesize the Okazaki fragment.

1,4,5,3,2

what proportion of chromosomes in a mans skin cell are maternal chromosomes?

1/2

Norway rats have 42 chromosomes in their diploid cells. If such a cell enters meiosis, how many chromosomes and double-helical molecules of DNA will be present in each daughter cell at the end of meiosis II?

21 chromosomes and 21 double-helical DNA molecules

If a cell contains 60 chromatids at the start of mitosis, how many chromosomes will be found in each daughter cell?

30 chromosomes

predict how many double helical DNA molecules will be present in the sperm and egg cells of dos, diploid animals that contain 78 replicated chromosomes in each cell that enters meiosis

39, because the number of replicated chromosomes is reduced at the end of meiosis 1

Meiosis of one diploid cell results in the production of what?

4 haploid cells

Telomerase synthesizes DNA in the ______ direction?

5'-3'

What is the probability that the following parents heterozygous for 3 traits will produce AaBbCc offspring?

8 chromosomes from each the mother and father...multiply them, so, 64 total gametes

What is a bivalent?

A bivalent is formed during prophase of meiosis I when the 2 homologous chromosomes in a pair (each composed of 2 sister chromatids) come together.

malignant tumor

A cancerous tumor that is invasive enough to impair the functions of one or more organs.

Explain the reason that distinct leading and lagging strands appear at each replication fork

A combination of two things causes this: DNA has antiparallel strands, and DNA can only be synthesized in the 5′ → 3′ direction. When these factors are put together, then one of the replicating strands follows the replication fork and the other moves away from it.

Codominance

A condition in which both alleles for a gene are fully expressed

explain why self-fertilization of a hybrid is equivalent to crossing two hybrid individuals f the same type together

A cross of two hybrids of the same type involves a cross of a male and a female; self-fertilization involves male and female gametes that should contain exactly the same genetic determinants as those from the cross between hybrids. Thus, it makes no difference whether the male and female gametes come from the same individual or different individuals if the individuals are the same type of hybrid.

What genotype in a mother and a father would be predicted to produce a 1 : 1 ratio of normal : colorblind offspring? From this mating, what would be the ratio of color-blind male : color-blind female?

A heterozygous female and a colorblind male. 1 color-blind male : 1 color-blind female.

DNA ligase

A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.

Predict which of these events would most rapidly arrest (stop) a replication fork: loss of topoisomerase or DNA helicase

A loss of DNA helicase activity would be expected to cause an immediate arrest of the replication fork, because helicase is responsible for opening the two strands of DNA. However, the arrest of the replication fork from loss of topoisomerase wouldn't be far behind—the replication fork would soon stop moving as the DNA strands ahead of the replication fork became twisted.

cyclin-dependent kinase

A protein kinase that is active only when attached to a particular cyclin.

Gene

A segment of DNA on a chromosome that codes for a specific trait

centrosome

A structure present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. A centrosome has two centrioles.

chromosome

A threadlike, gene-carrying structure found in the nucleus. Each chromosome consists of one very long DNA molecule and associated proteins.

How many gametes could be produced through independent assortment by an individual with the genotype AabbCcDD?

Aa(2) bb(1) Cc(2) DD(1) = 4 unique gametes

benign tumor

An abnormal mass of cells that remains at its original site in the body.

recessive allele

An allele that is masked when a dominant allele is present

dominant allele

An allele whose trait always shows up in the organism when the allele is present.

telomerase

An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells.

primase

An enzyme that joins RNA nucleotides to make the primer.

helicase

An enzyme that untwists the double helix of DNA at the replication forks.

Heterozygous

An organism that has two different alleles for a trait

Homozygous

An organism that has two identical alleles for a trait

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

somatic cells

Any cells in the body other than reproductive cells (body cells)

autosome

Any chromosome that is not a sex chromosome

Justify why two complementary single strands of DNA are considered two separate molecules, yet when these strands come together and form a double-stranded DNA, the doublestranded DNA is considered a single molecule of DNA.

Because a molecule is a group of atoms held together with chemical bonds, each separate strand of DNA meets this definition, as do the two hydrogen-bonded strands of DNA.

explain why mental needed to study two different genes rather than two different alleles of one gene in order to derive the principle of independent assortment

Because independent assortment considers the independence of the segregation of alleles of two or more distinct genes. At least two genes need to be considered, not one.

compare and contrast cytokinesis in plant and animal cells

Both of the cell types use cytokinesis to divide the cytoplasm into two daughter cells. Plant cells produce a cell plate that grows in the middle of the spindle and fuses with the plasma membrane. Animal cells use a cleavage furrow in the middle of there spindle to draw in the plasma membrane, which eventually fuses with itself.

How are Okazaki fragments synthesized?

By using the lagging-strand template, and synthesis 5'-3'

meiosis

Cell division that produces reproductive cells in sexually reproducing organisms

centrioles

Cell organelle that aids in cell division in animal cells only

sex chromosome

Chromosome associated with an individual's sex

meiosis metaphase 2

Chromosomes line up in the middle of the spindle

chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell

In eukaryotic cells, chromosomes are made up of what?

DNA and proteins

Allele

Different forms of a gene

chromatid

Each half of the chromosome (double stranded DNA copies in a replicated chromosome)

DNA polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

topoisomerase

Enzyme that functions in DNA replication, helping to relieve strain in the double helix ahead of the replication fork.

Nondisjunction

Error in meiosis in which homologous chromosomes fail to separate.

state how filling in the top and side of a punnett square is related to the principle of segregation and predict the offspring phenotype and genotype ratios for a cross between Rr and rr peas

Filling in the top and side of a Punnett square requires writing out the types of gametes. To do this, you have to understand how different forms of a gene (alleles) separate from one another—as described by the principle of segregation. The offspring phenotype ratios will be 1 round : 1 wrinkled; the offspring genotype ratios will be 1 Rr : 1 rr.

list where the four cell-cycle checkpoints occur in the cell cycle, and explain why they are important

G1, G2, M, & S - without these four checkpoints, cells could be overproduced in multicellular organisms, and cell division could result in daughter cells that are inviable or have defects in their genetic material.

explain how genetic variation would be affected if maternal chromosomes always lined up on one side of the metaphase plate during meiosis 1 and paternal chromosomes always lined up on the other side

Gametes would contain either maternal chromosomes only or paternal chromosomes only.

Explain how the 3 : 1 ratio of dominant to recessive offspring in the F2 generation led Mendel to conclude that the F1 hybrids produced gametes with a 1 : 1 ratio of dominant to recessive alleles.

If there was a biased transmission of one allele over another, say the dominant allele was present in a greater proportion of gametes than the recessive allele, then Mendel would have obtained ratios different from a 3 : 1 ratio. Only when there is a 1 : 1 mix of gametes with the dominant and the recessive alleles will there be a 3 dominant: 1 recessive ratio.

Explain why using an RrYy pea plant in a testcross produces a 1 : 1 : 1 : 1 ratio of offspring phenotypes, but self-fertilization produces a 9 : 3 : 3 : 1 ratio of offspring phenotypes.

In a testcross, one of the parents is always a homozygous recessive strain. The only type of gamete produced by this strain contains recessive alleles of every gene considered in the cross. Given this, coupled with the finding that an RrYy strain produces 4 gamete genotypes in equal proportions, indicates that 4 different offspring phenotypes, each in equal amounts, are expected. In contrast, self-fertilization of an RrYy strain involves 4 different gamete genotypes, each in equal amounts, present in both sperm and egg cells. With dominant and recessive alleles for each gene, the offspring phenotypes will occur in a 9 : 3 : 3 : 1 ratio.

Explain the differences between the conservative and semi conservative DNA replication hypotheses.

In the conservative replication hypothesis, the parental double-strandedDNA molecule would remain intact after replication and a daughter DNA molecule would be created with both strands new. By contrast, in the semi conservative replication hypothesis (the correct hypothesis), each of the DNA molecules found after replication would contain one parental (Old) strand and one daughter (newly replicated) strand of DNA

Explain why the simplest drawing to model the principle of independent assortment requires four chromosomes, but the simplest drawing to model the principle of segregation requires only two chromosomes.

Independent assortment involves independent segregation of the alleles of two separate genes on separate chromosomes. Therefore, the simplest model of independent assortment requires drawing at least 4 chromosomes shown as two homologous pairs. Conversely, because segregation considers the separation of the two copies of a single gene carried on a single type of chromosome, only the two chromosomes of one homologous pair need to be drawn.

Which of the following is not a property of DNA polymerase?

It opens the two strands of DNA at the replication fork

autosomal inheritance

Inheritance of a genetic trait not on a sex chromosome

Explain how the disappearance of one of the two parental traits in the F1 generation and the reappearance of that trait in the F2 generation led Mendel to conclude that there were two copies of a gene for each trait.

Mendel came to this conclusion for two reasons: (a) The results could not be explained if each individual had only one copy of a gene. With only a single gene for each trait, the offspring would inherit one of the parental genotypes, and it would lead to a mix of F1 offspring phenotypes, depending on which parental allele was inherited. The reappearance of the recessive trait in 1/4 of the F2 offspring could also not be explained if offspring had inherited only one allele of each gene from one or the other of their parents. (b) While more complicated models with many copies of each gene might possibly be fit to the data, he applied the principle that the simplest model is the most likely explanation for the results.

hybrid

Offspring from crosses between homozygous parents with different genotypes

In Hershey and Chase's actual study, there was a trace amount of radioactive slur in the pellet of cells that formed after centrifugation. Explain how this might have occurred, although their hypothesis was correct.

One explanation is that the procedure used to remove viral capsize was not perfectly efficient, allowing some of the viral cap side that contain radioactive sulfur in the proteins to remain attached to the cells.

synapsis

Pairing of homologous chromosomes

cell-cycle checkpoints

Points of transition between different phases of the cell cycle, which are regulated by cyclins and cyclin-dependent kinases (Cdk's).

cell division

Process by which a cell divides into two new daughter cells (cells are formed by the splitting of pre-existing cells)

single-stranded binding proteins

Proteins that act as scaffolding, holding two DNA strands apart during replication

centromere

Region of a chromosome where the two sister chromatids attach

Okazaki fragments

Small fragments of DNA produced on the lagging strand during DNA replication, joined later by DNA ligase to form a complete strand.

origin of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

incomplete dominance

Situation in which one allele is not completely dominant over another allele

microtubules

Spiral strands of protein molecules that form a tubelike structure

In flies, small wings are recessive to normal wings. If a cross between two flies produces 8 small wing offspring and 28 normal wing offspring, what are the most likely genotypes of the parents? (Use S to represent the normal wing allele and s to represent the short wing allele.)

Ss for both parents

How does telomerase prevent linear chromosomes from shortening during replication?

Telomerase binds to the overhand at the end of a chromosome. Once bound, and using its RNA template as a guide, it begins catalyzing the addition of deoxyribonucletides to the overhand in the 5'-3' direction

Triploid (3n) watermelons, which are seedless, are produced by crossing a tetraploid (4n) strain with a diploid (2n) plant. Explain why this mating produces a triploid individual.

Tetraploid produce diploid gametes, which combine with a haploid gamete from a diploid individual to form a triploid offspring. Mitosis proceeds normally in triploid cells because mitosis doesn't require forming pairs of chromosomes. But during meiosis in a triploid homologous chromosomes can't pair up correctly. The third set of chromosomes does not have a homologous partner to pair with.

Describe the differences at the molecular level between the 5' and 3' ends of a DNA strand

The 5' end of a DNA strand has a phosphate group attached to one of the carbons of the sugar that is at one end of the chain, and the 3' end of a DNA strand has a hydroxyl (-OH) group attached to a different carbon of the sugar that is at the other end of the chain.

pleiotropy

The ability of a single gene to have multiple effects.

cleavage furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell

mismatch repair

The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.

compare and contrast the roles of the two gap phases in the eukaryotic cell cycle

The gap phases are periods of the cell cycle when there is no DNA synthesis (S phase) and no separation of the chromosomes or cytoplasm (M phase). In the G1 phase, cells perform their normal functions and "decide" when or if the cell undergoes division. In the G2 phase, cells contain replicated chromosomes as they grow and prepare for M phase.

Explain how the short repetitive DNA sequences of telomeres arise during replication of chromosome ends.

The short repetitive DNAs come from repetitively copying the RNA template in telomerase that codes for this repeat. Doing this over and over creates the many copies.

Explain why primate works more often on the lagging strand than on the leading strand.

The leading (continuous) strand is a long strand that requires only one primer, but the lagging (discontinuous) strand is made of a set of short DNA fragments (Okazaki fragments), each of which requires an RNA primer and therefore primase

Explain why in Nilsson-Ehle's genetic model, 1/64 of the F2 offspring were predicted to be white and 1/64 of these offspring were expected to be dark red.

The lightest (white) and darkest color phenotypes are each associated with single genotypes (aabbcc or AABBCC). Given that the F2 was produced by self-fertilization of a fully heterozygous F1 (AaBbCc), 8 gamete types are expected to be produced with independent assortment. One of these gamete types is abc, and another is ABC. The chance that a sperm and an egg carrying identical gamete genotypes come together at fertilization to produce either of the aabbcc or AABBCC genotypes is given by the product of the gamete frequencies, or 1/8 × 1/8 = 1/64.

Explain why the mass difference between 14N and 15N was important in measles on and Stahl's investigation.

The mass difference allowed the researcher to distinguish DNA strands before any rounds of replication began from DNA strands that were replicated after the study started. making this distinction is at the heart of the Meselson-Stahl experiment.

What aspect of DNA structure makes it possible for the proteins of nucleotide excision repair to recognize many different types of DNA damage?

The regulatory of DNA's structure

explain how DNA content is reduced by half during both meiosis 1 and mitosis, yet chromosome number is reduced only during meiosis 1

The separation of homologous chromosomes at meiosis 1 reduces both chromosome number and DNA amount in each of the daughter cells.

metastasis

The spread of cancer cells beyond their original site

Explain why the DNA template strand with a 3' end cannot be replicated to its end, but the template strand with a 5' end can be.

The strand with a 3' end cannot be replicated to its end because when it is used as a template, the complementary newly synthesized strand must be made in a direction that moves from the region near the 3' end toward the other end of the chromosome. Given that an RNA primer is needed to start DNA synthesis, this means that this template strand isn't replicated to its end. In contrast, when the strand terminating with a 5' end is used as a template, the newly replicated strand grows toward the end of the chromosome and can be extended all the way to the 5' end.

kinetochores

The structures on sister chromatids where microtubules attach

S phase (synthesis)

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

Outline a study to test whether individuals who share the same genotype of one gene, say aa, but express different phenotypes influenced by this genotype do so because of gene interaction or because of environmental effects.

There are many ways to construct this study, but the basic idea is to set up two different situations: produce through crosses a set of individuals that share the same genotype at the gene in question (for example, aa) but are genetically variable at other genes. Raise and maintain these individuals in the same environment. If there are differences in phenotype, then these differences are likely due to gene interaction. Contrast this experimental strategy with one in which individuals are genetically identical across all genotypes and are raised and maintained in a set of different environments. If there is strong variation in phenotype in this case, then differences in phenotype are due to environmental effects. Gene interaction and environmental effects are not mutually exclusive, and both may play roles in the phenotypic variation of individuals who share a genotype at one gene.

If you understand the events of meiosis, you should be able to predict how many DNA molecules will be present in the gametes of the fruit fly Drosophila, a diploid organism that has eight replicated chromosomes in each cell that enters meiosis.

There will be four DNA molecules in each gamete because the 8 replicated chromosomes in a diploid cell are reduced to 4 replicated chromosomes per cell at the end of meiosis I. In meiosis II, the sister chromatids of each replicated chromosome are separated. Each cell now contains 4 unreplicated chromosomes, each with a single molecule of DNA.

Explain the two types of movement that are responsible for separating daughter chromosomes during anaphase.

Type 1: the shrinkage of kinetochore microtubules transports daughter chromosomes to the opposite poles of the spindle. Type 2: the push against polar microtubules by motor proteins and the pull on astral microtubules by other motors on the plasma membrane move the spindle poles to opposite sides of the cell.

replicated chromosome

a chromosome after DNA replication. consists of 2 identical chromatids, each containing one double helical DNA molecule packaged with proteins

unreplicated chromosome

a chromosome that consists of one double helical molecule of DNA packaged with proteins

reciprocal cross

a cross in which the phenotypes of the male and female are reversed compared with a prior cross

testcross

a cross of a homozygous recessive individual and an individual with the dominant phenotype but unknown genotype

sex-linkage

a gene located on a sex chromosome

epistasis

a particular form of gene interaction in which particular alleles of one gene mask the expression of alleles at another gene

gene

a region of DNA is a chromosome that codes for a particular protein or ribonucleic acid (RNA)

Identify at least two events in the cell cycle that must be completed successfully for daughter cells to share an identical complement of chromosomes.

all of the chromosomes must be replicated during S phase, the spindle apparatus must connect with the kinetochores of each sister chromatid in pro metaphase, the sister chromatids of each replicated chromosome must be divided between two daughter cells by cytokinesis

gap phases

allow the cell to grow and respond to environmental cues.

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?

at the end of meiosis 1

explain why mitosis in a triploid (3n) cell can occur easily but meiosis is difficult

because mitosis separates sister chromatids of single chromosomes and there is no need for homologous chromosomes to pair

When does DNA polymerase perform its proofreading function on mismatched nucleotides?

before adding the next nucleotide

A biochemist measured the amount of DNA in cells growing in the lab and found that the quantity of DNA in a cell doubled....where?

between G1 and G2 phases

conservative replication

both strands of the initial DNA molecules would be kept or conserved

compare and contrast benign and malignant tumors

both types of tumors have unregulated cell division. However, benign tumors remain localized to a single mass and do not invade other tissues, while malignant tumors spread from the original tumor and may metastasize to distant locations

Meiosis 2: Cytokinesis

cell divides; chromosomes number is unchanged

mitosis

cell division in which the nucleus divides into nuclei containing the same number of chromosomes

sister chromatids

chromatid copies that remain attached at their centromere

Meiosis: Early Prophase I

chromosomes condense, pairing of homologous chromosomes

Meiosis Interphase

chromosomes duplicate

What are homologous chromosomes?

chromosomes that are similar in their size, shape, and gene content.

Meiosis: Late Prophase I

crossover points visible, nuclear envelope is broken down

Progression through the cell cycle is regulated by oscillations in the concentration of which type of molecule?

cyclins

meiosis telophase 2

daughter chromosomes are at opposite poles; spindle disassembles

What evidence suggests that during anaphase, kinetochore microtubules shorten at the kinetochore?

daughter chromosomes were observed to move toward the poles faster than the marked regions of fluorescently labeled kinetochore microtubules

cytokinesis

division of the cytoplasm into two distinct cells

semiconservative DNA replication

each daughter DNA molecule is composed of one original strand and one new strand

The alleles found in haploid organisms cannot be dominant or recessive. Why?

dominance and recessiveness describe which of two possible phenotypes are exhibited when two different alleles occur in the same individual

tumor suppressors

encode proteins whose normal activities inhibit cell division

T/F crossing over occurs between sister chromatids

false

T/F non-sister chromatids are found on different homologs

false

T/F sister chromatids are homologous chromosomes

false

T/F genetic map of distances measure the number of nucleotides between a pair of genes

false; genetic map distances measure the frequency of crossing over between a pair of genes

T/F linked genes are always inherited together

false; linked genes are separated by crossing over in meiosis

If two of the purple-flowered F1 offspring were randomly selected and crossed, what is the expected ratio of genotypes and phenotypes among the F2 offspring?

genotype: 1PP:2Pp:1pp phenotype: 3 purple : 1 white

In peas, purple is dominant over white for flower color. if a purple-flowered heterozygous plant were crossed with a white-flowered plant, what is the expected ratio of genotypes and phenotypes among the F1 offspring?

genotype: 1Pp:1pp phenotype: 1 purple flower : 1 white flower

explain how growth factors allow cells to bypass the G1 checkpoint and enter S phase

growth factors activate the expression of E2F and cyclins. The cyclins bind to a Cdk to phosphorylate Rb, which releases E2F to promote expression of S-phase specific genes.

polyploid

having more that two of each type of chromosome: may be triploid (3n), tetraploid (4n), hexaploid (6n), etc.

haploid

having one of each type of chromosome

diploid

having two of each type of chromosome

spindle fibers

help pull apart the cell during replication and are made up of micrtubules

Meiosis Metaphase 1

homologous pairs align independently at the equator

Meiosis Anaphase 1

homologous pairs separate and are pulled to opposite poles of cell; this is called disjunction when they are pulled apart; daughter cells get a mixture of mom and dads chromosomes

pure line

individuals of the same phenotype that, when crossed, always produce offspring with the same phenotype

leading strand (continuous strand)

in DNA replication, the new strand of DNA that is synthesized in one continuous piece in a direction that follows the replication fork

multiple allelism

in a population, there are more than two common alleles for a locus

M-phase-promoting-factor (MPF)

induces M phase in all eukaryotes

kinetochore motor

kinetochore contains dyneins and other motor proteins. They are attached to the kinetochore's fibrous crown & are capable of "walking" down microtubules from their plus ends near the kinetochore toward their minus ends at the spindle.

nondisjunction that leads to problems in offspring occur in

meiosis 1 and 2

During what phases in the cell cycle would you expect there to be large changes in the polymerization or depolymerization of microtubules? Why are these changes necessary?

microtubules are actively polymerized during the start of M phase, when the mitotic spindle is produced. During anaphase, the kinetochore microtubules are depolymerized as daughter chromosomes move to opposite poles of the cell. At the end of M phase, the spindle microtubules are depolymerized to remove the spindle before entering G1.

State the haploid number, ploidy, and total number of chromosomes present in a male Drosophila.

n=4, the organism is diploid, 2n=8

M Phase (mitosis or meiosis)

occurs when cells are in the process of separating their chromosomes

The genes for the traits that Mendel worked with are either located on different chromosomes or behave as if they were How did this help Mendel recognize the principle of independent assortment?

otherwise his dihybrid crosses would not have produced a 9:3:3:1 ratio of F2 phenotypes

environmental effects

phenotype influenced by both genotype and the environment

apoptosis

programmed cell death

telomere

repetitive DNA at the end of a eukaryotic chromosome

cyclins

proteins that regulate the timing of the cell cycle in eukaryotic cells

Meiosis Cytokinesis

reduces chromosome number, cell divides

x-linkage (x-linked)

referring to a gene located on the X chromosome or a trait associated with a gene on the X chromosome

y-linkage (y-linked)

referring to a gene located on the Y chromosome or a trait associated with a gene on the Y chromosome

DNA replication at the ends of linear chromosomes requires the special enzyme telomerase because...

removal of the last RNA primer on the lagging strand leaves a recessed end that the DNA

dispersive replication

replication results in both original and new DNA dispersed among the two daughter strands

gametes

reproductive cells (sperm and eggs)

cell cycle

series of events that cells go through as they grow and divide

Meiosis anaphase 2

sister chromatids separate and move to opposite poles

Chiasma

site of crossing over

Meiosis Propahse 2

spindles form in each haploid daughter cell and attaches to the centromere to move the individual chromosomes to the middle of the cell

spindle apparatus

structure made of spindle fibers, centrioles, and aster fibers that is involved in moving and organizing chromosomes before the cell divides

What is the function of primase?

synthesis of a short RNA strand that is complementary to single-stranded DNA

replication fork

the Y-shaped region where the parental DNA double helix is separated into single strands and copied

Compare and contrast the effects of removing growth factors from asynchronous cultures of human cells hat are normal and those that are cancerous.

the absence of growth factors in normal cells would cause the cells to arrest in G1 phase, and eventually all the cells in the culture would be in G1. The cancerous cells would be unlikely to depend on these growth factors, so those cells would not arrest and would continue through the cell cycle

When a fruit fly embryo first begins to develop, a large cell is generated that contains over 8000 genetically identical nuclei. What is most likely responsible for this result?

the embryo passes through multiple rounds of the cell cycle, but cytokinesis does not occur during the M phases

Explain how a single allele can exhibit both complete dominance and codominance.

the form of dominance of an allele is relative to that of another particular allele. This means that if one allele is paired with another, say IA with i, IA may be dominant to i, but if IA is paired with a different allele, say IB, IA may be codominant with IB.

what is the outcome of genetic recombination?

the new combination of maternal and paternal chromosome segments that results when homologs cross over

diploid number

the number of chromosomes present in a diploid cell; symbolized 2n

haploid number

the number of different types of chromosomes in a cell; symbolized by n

ploidy

the number of each type of chromosome

gene interaction

the phenotype associated with an allele depends on which alleles of another gene are present

interphase

the resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.

What major events occur during anaphase of mitosis?

the sister chromatids on replicated chromosomes separate, and the spindle poles are pushed farther apart

Why is the pea wrinkled-seed allele a recessive allele?

the trait associated with the allele is not exhibited in heterozygotes

Which statement about the daughter cells following mitosis and cytokinesis is correct?

they are genetically identical to each other and to the parent cell

polygenic traits

traits controlled by two or more genes

T/F crossing over occurs between genes on different homologs of a homologous chromosome pair

true

T/F the farther apart genes are on a chromosome, the more likely there is to be a crossover between these genes during meiosis

true

p53 protein

tumor-suppressor protein that responds to DNA damage by stopping the cell cycle and triggering apoptosis

linkage

two or more genes are on the same chromosome

After S phase, what makes up a single chromosome?

two sister chromatids

excision repair system

works on DNA damage caused by ultraviolet light and many different chemicals