BIOL Unit 1 Review

Describe the process of binary fission in bacteria (The type of cell division for Prokaryotes) (Have DNA but no nucleus)

The bacterial chromosome, a single circular DNA molecule, begins to replicate at the origin of replication and one of these duplicated origins moves to the opposite pole of the cell. The 2 daughter chromosomes actively move apart. Replication is completed as the cell doubles in size, and the plasma membrane pinches inward to divide the two identical daughter cells.

Define Polyploidy:

* A condition in which an organism has more than 2 complete sets of chromosomes. *Common in plants, not animals. *more normal in appearance that aneuploids. *One extra chromosome, one less

Explain why extranuclear genes are not inherited in a Mendelian fashion

* The only extranuclear genes possessed by any organisms are the genes in mitochondria (and, in plants, in chloroplasts). During sexual reproduction (in either plants or animals), it is only the nuclear genes which are passed-down from the male partner. The sperm (or pollen grain) contributes a nucleus, but no mitochondria (or chloroplasts). The mitochondria (or chloroplasts) are only found in the egg cell - so they are only inherited from the female partner.

Define: Monohybrid cross

*A mating between 2 individuals who have different alleles at one genetic locus of interest

Explain the significance of the research of Rosalind Franklin

*After DNA was accepted as the genetic material, the challenge was to determine how its structure accounts for its role in heredity. Wilkins and Franklin used a technique called X-ray crystallography to study molecular structure. Franklin produced a picture of the DNA molecule and Watson used that to deduce DNA was helical.

Compare cytokinesis in animals and plants.

*Animals: the cell splits by process known as cleavage into two with a cleavage furrow made of microfilaments in the middle *Plants: a cell plate forms in between the splitting cells. Plants have a cell wall so they cannot duplicate the same as animal cells. Vesicles form a cell plate then the wall of parent cell forms the cell plate and a new cell wall forms daughter cells.

Distinguish between asexual and sexual reproduction.

*Asexual Reproduction: is a form of reproduction which w/o meiosis, ploidy reduction, fertilization and without fusion of gametes. one parent produces genetically identical offspring by mitosis. (clone) *Sexual Reproduction: Is 2 processes: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve genetic recombination.

List the phases of the cell cycle and describe the sequence of events that occurs during each phase. ~INTERPHASE~ 90% cell cycle

*INTERPHASE: Cell growth and copying of chromosomes in preparation for cell division. Cell grows in all phases, but chromosomes are only duplicated in S PHASE *G1 Phase: all cellular contents of the cell, excluding the chromosomes are duplicated. The cell grows, ensures it has enough nutrients, and space. *S phase: Cell receives signal and the chromosomes are all duplicated. *G2 phase: where the cell double checks for error and ensure the chromosomes were duplicated properly.Cell continues to grow. Chromosomes replicate but are not visible as discrete structures. Centrosomes duplicate.

Define Triploidy:

*(3n) Is three sets of chromosomes

~Describe the process of DNA replication, including the role of the origins of replication and replication forks ~Explain the role of DNA polymerase in replication ~Distinguish between the leading strand and the lagging strand ~Explain how the lagging strand is synthesized even though DNA polymerase can add nucleotides only to the 3' end. ~Describe the significance of Okazaki fragments ~Explain the roles of DNA ligase, primer, primase and helicase.

*At the origin of replication, the 2 strands separate serving as templates for making new strands. This results in a replication bubble. Eukaryotic chromosome has many origins of replication. *At the end of each replication bubble is a replication fork, a Y-shaped region where new DNA strands are elongating. *Helicases are enzymes that untwist the double helix at replication forks. (Opens the 2 strands at fork) *Single-strand binding proteins bind to and stabilize single-stranded DNA. Only binds after replication fork. It prevents Hydrogen bonds between the bases of the parental DNA and from them rejoining. *An initial nucleotide strand, a short RNA primer, must be added in order for it to start replicating somewhere. *An enzyme called primase (an RNA primer), can start an RNA chain and adds RNA nucleotides one at a time using parental DNA as template. Primer is short, 5-10 nucleotides long, and the 3' end serves as the staring point for the new DNA strand. *Topoisomerase: breaks a covalent bond in backbone of parent strand to relieve strain caused by unwinding of DNA. It binds ahead of the replication fork and repairs broken bond. *DNA polymerase III: Adds nucleotides to the 3' end but does not initiate synthesis, primase does. *Leading strand: one of the strands that is built continuously *Lagging strand: built in pieces or fragments (Okazaki strands) *Synthesis of the Leading strand: DNA polymerase III builds a new strand of DNA by adding DNA nucleotides one at a time. Each new nucleotide must pair up with its complementary pair. (adding new nucleotides works same with both leading and lagging). *Synthesis of Lagging strand: Each piece begins with a short segment of RNA. A clamp surrounds RNA and attaches to DNA polymerase III which builds the rest of the new piece of DNA. Once that fragment is finished, it is released and pieces of lagging strand are joined together by DNA polymerase I that removes RNA and replaces it with DNA, but does not connect them. An enzyme called DNA Lygase joins the fragments together. *New daughter strands run antiparallel to parental strands.

Distinguish between autosome and sex chromosome:

*Autosome: Any chromosome except the X & Y chromosome (22 chromosomes) *Sex Chromosome: The X & Y chromosome that distinguishes the sex

Compare a bacterial chromosome and a eukaryotic chromosome.

*Bacterial chromosome:" A double-stranded, circular DNA molecule associated with a small amount of protein. Bacterial DNA condenses by supercoiling into a tight ball, nucleoid. *Eukaryotic chromosome: have linear DNA molecules associated with a large amount of protein. Chromatin, a complex of DNA and protein, is found in the nucleus. Chromosomes fit through an elaborate multilevel system of packing. *Bacterial chromosomes don't have non-coding regions or introns.

Explain why linked genes do not assort independently. Explain how crossing over can unlink genes.

*Because linked genes are within the same chromosome. In order for independent assortment to occur, the genes must be on different chromosomes. *Crossing over can unlink genes because if it occurs between the two loci, then they will be separated and will unlink.

Explain how Mendel's particulate mechanism differed from the blending of theory of inheritance.

*Blending theory: Idea that genetic material from the 2 parents blends together (blue and yellow blends to make green) *Particulate theory: Idea that parents pass on discrete heritable units (genes) (retain separate identities like a deck of card shuffled) ~This hypothesis can explain why the reappearance of traits after several generations~

Describe the polymerase chain reaction (PCR) and explain the advantages and limitations of this procedure.

*Can produce many copies of a specific target segment of DNA (Millions from one original copy) *Goal is to amplify a specific region, the target DNA *Solution contains Taq polymerase which is a heat stable DNA polymerase. It continues to function normally at high temperatures which allows researchers to separate DNA strands using heat w/o destroying polymerase. Cycle repeated 35 times. 1.) DENATURATION: solution heated to 95*C. The heat breaks hydrogen bonds between DNA strands and separate. Taq polymerase remains active despite heat 2.) PRIMER ANNEALING: Temp dropped to 60*C. At this lower temp, primers can form hydrogen bonds w/ single-stranded DNA. 2 primer types created, each complementary in sequence to one of the two ends of target DNA. To make primers, sequences at the ends of target DNA must be known. 3.) EXTENSION: Temp increased to 72*C optimal temp at which Taq polymerase functions. Primers are essential because they provide free 3' hydroxyl groups, to which the polymerase can add additional dNTP's. Each new dNTP that joins growing strand is complementary to nucleotide in opposite strand. *Advantages: Quick way to have millions of duplicates of a DNA fragment from just one copy *Limitations: Can only copy a short segment, not all DNA

Explain the effect of multiple crossovers between loci

*Cause underestimation of distance?

Describe the inheritance of the ABO blood system and explain why the IA and IB alleles are said to be codominant.

*Codominance: two dominant alleles affect the phenotype in separate, distinguishable ways. *the enzyme encoded by the IA allele adds the A carbohydrate, enzyme encoded by IB allele adds the B carbohydrate. The enzyme encoded by the i allele adds neither. *They are codominant because carbohydrates A and B can be on the same cell.

Explain the roles of DNA polymerase, mismatch repair enzymes and nuclease in DNA proofreading and repair

*DNA Polymerases: proofread newly made DNA, replacing any incorrect nucleotides *In Mismatch repair: of DNA, repair enzymes correct errors in base pairing, usually as they're made. *a Nuclease: a nucleotide excision repair, cuts out and replaces damaged stretches of DNA. So nuclease cuts out a piece of DNA, DNA polymerase fills the gap, and lygase seals them.

Distinguish among deletions, duplications, inversions, and translocations.

*Deletion: removes a chromosomal segment *Duplication: repeats a segment *Inversion: reverses a segment within a chromosome *Translocation: moves a segment from one chromosome to a nonhomologous chromosome

Distinguish between dominant and recessive:

*Dominant: determines organism's appearance *Recessive: has no noticeable effect on appearance

State Mendel's law of independent assortment and describe how this law can be explained by the behavior of chromosomes during meiosis.

*Each pair of alleles segregates independently of other pair of alleles during gamete formation *Only applies to genes on different, non-homologous chromosomes or those far apart on the same chromosome (not for linked genes)

Explain how the creation of sticky ends by restriction enzymes is useful in producing a recombinant DNA molecule

*Hundreds of restriction enzymes known, each cuts at specific sites leaving the same complementary ends. Mixing DNAs allows for the sticky ends to bind. DNA ligase seals backbones and recombinant DNA is created. *The most useful restriction enzyme cleave the DNA in a staggered manner to produce sticky end which can bond to complementary sticky ends of other fragments. Which allows a recombinant DNA molecule to be formed.

List the phases of meiosis 1 and Meiosis 2 and describe the events and characteristics of each phase. Recognize the phases of meiosis from diagrams.

*First division (MEIOSIS I) separates homologous chromosomes Results in 2 daughter cells with duplicated chromosomes. (n) *Prophase I: Chromosomes coil & compact. Homologous pairs come together by synapsis. Each pair with 4 chromatids is called a tetrad. Non-sister chromatids exchange genetic info by crossing over (location: chiasmata) to increase genetic variation *Metaphase I: Tetrads align at the cell equator (46 chromosomes present (23 pairs) 92 chromatids present, 2 per chromosome) *Anaphase I: Homologous pairs separate and move toward opposite poles of cell. (Sister chromatids stay attached) *Telophase I: Duplicated chromosomes reached the poles, nuclear envelope forms, each nucleus has haploid number *Cytokinesis: 2 haploid cells result. (23 chromosomes in one cell, 46 chromatids present) *Second division (MEIOSIS II) separates sister chromatids. Results in 4 daughter cells with half as many chromosomes as parent cells. with unduplicated chromosomes. (n) *Prophase II: Chromosomes coil and become compact *Metaphase II: Duplicated chromosomes align at the cell equator *Anaphase II: Sister chromatids separate and chromosomes move toward opposite poles *Telophase II: Chromosomes reach opposite poles of cell. Nuclear envelope forms around each set of chromosomes *Cytokinesis II: Forms 4 haploid cells. (23 chromosomes present in one cell, 0 chromatids (unreplicated, reffered to as a chromosome, no longer chromatid))

Define: F1 generation

*First offspring (hybrid) from a cross of 2 varieties int eh P generation. shows all dominant traits (all purple)

Explain how Watson and Crick deduced the structure of DNA and describe the evidence they used.

*Franklin's X-ray of crystallographic images of DNA enabled Watson to deduce that DNA was helical *The X-ray images also enabled Watson to deduce the width of the Helix and the spacing of the nitrogenous bases. The pattern in the photo suggested that the DNA molecule was made up of 2 strands, forming a double helix.

Explain how the experiments performed by the following scientists provided evidence that DNA is a genetic material. ~Frederick Griffith ~Alfred Hershey and Martha Chase ~Erwin Chargaff

*Frederick Griffith: He worked with 2 strains of bacterium, one pathogenic and one harmless. When he mixed heat-killed remains of the pathogenic strain with living cells of the harmless strain, some living cells became pathogenic. This phenomenon was called "Transformation" (assimilation of foreign DNA). 16 years later another group of scientists announced that the transforming substance was DNA based on experimental evidence that only DNA worked in transforming harmless bacteria into pathogenic bacteria. *Alfred Hershey and Martha Chase: performed experiments showing that DNA is the genetic material of a phage known as T2. They designed an experiment showing that only one of the 2 components of T2 (DNA or PROTEIN) enters an E. coli cell during infection. They used radioactive isotopes. -In a first experiment, they labeled the DNA of phages with radioactive Phosphorus-32 (the element phosphorus is present in DNA but not present in any of the 20 amino acids from which proteins are made). They allowed the phages to infect E. coli, then removed the protein shells from the infected cells with a blender and separated the cells and viral coats by using a centrifuge. They found that the radioactive tracer was visible only in the pellet of bacterial cells and not in the supernatant containing the protein shells. In a second experiment, they labeled the phages with radioactive Sulfur-35 (Sulfur is present in the amino acids cysteine and methionine, but not in DNA). After separation, the radioactive tracer then was found in the protein shells, but not in the infected bacteria, supporting the hypothesis that the genetic material which infects the bacteria is DNA. ~Erwin Chargaff: He reported that DNA composition varies from one species to the next. The evidence of diversity made DNA a more credible candidate for the genetic material. Chargaff's rules: 1.) The base composition of DNA varies between species, 2.) In any species the number of A and T bases are equal and the number of G and c bases are equal.

Describe the structure of DNA. Explain the base-pairing rule and describe its significance.

*From most basic to most complex. A nucleotide is the basic unit of DNA structure, the "monomer of DNA." A monomer is a small molecule that gets repeated many times to form a large molecule called a polymer. *The structure of a nucleotide monomer: the center or the deoxyribose is the molecule of sugar (constant in each nucleotide) and has 5 sides. Phosphate molecule on the left is the chemical group that contains an atom of phosphorous surrounded by 4 oxygen atoms. Nitrogen base is on the right side of sugar. There are 4 bases (A T C G) 2 of them have one hexagonal ring (Cytosine and Thymine are PYRIMIDINE), 2 have 2 rings, one 5 sided and one 6 sided (Adenine and Guanine are PURINE) In DNA polymer, one nucleotide is bonded to the sugar of the next nucleotide. A DNA strand is a polynucleotide, a polymer made from nucleotides.2 polynucleotides strands stick together forming one molecule of DNA. Hydrogen bonds hold bases together in properly matched pairs. Molecule of DNA twists around itself in a double helix. Outside are the two sugar and phosphate backbones and bases in middle hold it together. *Adenine (A) and Thymine (T) are complementary. They have 2 hydrogen bonds. The amount of A=T *Guanine (G) and Cytosine (C) are complementary. They have 3 hydrogen bonds. The amount of G=C *Purine and Pyrimidine width is consistent with x-ray data *A & T bond easier to break than the G & C because it has one less hydrogen bond. *Between phosphodiester bonds (Phosphorous and sugar) and hydrogen bonds, hydrogen bonds separate most easily.

Distinguish between genotype and phenotype:

*Genotype: genetic makeup *Phenotype: physical appearance -An organism's traits do not always reveal its genetic composition

Explain how haploid and diploid cells differ from each other; state which cells in the human body are diploid and which are haploid.

*Haploid cells (n): have half the 46 chromosomes, so 23. Only the sperm cells in the ova are haploid (one set) *Diploid cells (2n): have the full set of 46 chromosomes. Body cells are mostly all diploid (two sets)

Explain how the Sturtevant created linkage maps. Define a map unit.

*He used recombination frequencies to make linkage maps of fruit fly genes. He believed that the further apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency. *Map unit: the difference between chromosome positions; a unit for measuring genetic linkage

Distinguish between Heterochromatin and Euchromatin

*Heterochromatin: a few highly condensed regions of chromatin (centromeres and telomeres). During interphase. -Dense packing of heterochromatin makes it difficult for the cell to express genetic info coded in these regions Euchromatin: Loosely packed chromatin "True-chromatin" contains genes.

Distinguish between heterozygous and homozygous:

*Heterozygous: A dominant and a recessive allele, shows as if dominant (Aa) *Homozygous: Can be both dominant alleles or both recessive alleles (AA) or (aa) -2 identical alleles for characteristics

Describe a simple model for polygenic inheritance and explain why most polygenic characters are described in quantitative terms.

*Polygenic inheritance: several genes dictating a particular trait *Quantitative characters: are those that vary in the population along a continuum *Usually indicates polygenic inheritance, an additive effect of 2 or more genes on a single phenotype (Skin color) (Height)

Describe the process of X inactivation in female mammals. Explain how this phenomenon produces the tortoiseshell collaboration in cats.

*If a female is heterozygous for a particular gene located on the x chromosome, she would be a mosaic for that character. *If female is heterozygous for a gene on X chromosome, she is a mosaic for that character. *Tortoiseshell example: X-linked heterozygous genes randomly turned off Black allele on one X; orange allele on the other Half of the cells have inactivated black, the other orange

Explain how nondisjunction can lead to aneuploidy.

*In nondisjunction, pairs of homologous chromosomes do not separate normally during meiosis. *As a result, one gamete receives 2 of the same type of chromosome, and another gamete receives no copy. (Happens in meiosis I or II) *Offspring with aneuploidy have an abnormal number of a particular chromosome

Give an example of incomplete dominance and explain why it does not support the blending theory of inheritance

*Incomplete dominance: The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties *interbreeding F1 hybrids (Pink made from red and white parents) produces F2 offspring with a phenotypic ratio of one red to two pink to one white. because heterozygous have a seperate phenotype, the genotypic and phenotypic ratios for the F2 are the same 1:2:1 *Doesn't support the blending theory of inheritance because it does not get its colour from the dominant plant in this case but from both.

Explain how independent assortment, crossing over, and random fertilization contribute to genetic variation in sexually reproducing organisms.

*Independent assortment: random lining up of the homologues during metaphase I of meiosis I. More than 8 million combinations possible *Crossing over: involves the switching of genes between the non-sister chromatids of homologous chromsomes which allows the novel mixture of maternal and paternal genetic material with new, recombinant chromosomes. *Random fertilization: it is complete random which sperm fertilizes which egg which creates even more potential variation in the offspring.

Describe the internal and external factors that influence the cell cycle control system.

*Internal signal: example- kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase *External signal: some external signals are growth factors, proteins released by certain cells that stimulate other cells to divide. *An external factor could be the fibroblasts which give a signal for the cell to go past the G1 checkpoint.

Explain how gel electrophoresis is used to analyze nucleic acids and to distinguish between the 2 alleles of a gene.

*It sorts DNA molecules based on size. The bigger the molecule is, the harder time it has moving through the gel, hence why the smaller molecules end up near the positive end. You can do this to several DNA molecules and compare them side by side and determine which DNA molecules have the same alleles because they will be lined up exactly. *This technique separates a mixture of nucleic acid based on length.

Explain why genetic dominance does not mean that the dominant allele subdues a recessive allele.

*It's not a matter of force, it's a matter of expression. Alleles don't interact that way *Alleles are variations in a gene's nucleotide sequence.

Describe how the packing of chromatin changes during the course of the cell cycle.

*Level of looseness has to do with genes being expressed and proteins being produced. DNA encode info to produce proteins. *They are negatively charged *In interphase, the chromatin is highly extended. Preparing for mitosis, the chromatin coils or condenses and forms chromosomes in metaphase. *Chromosomes consist of loops of supercoils, which are made up of tight helical fibers. These fibers are composed of nucleosomes, which consist of DNA wrapped around protein molecules. *In fiber, DNA unavailable for transcription, must unpack fiber to make it accessible for transfer. *Each nucleosome consists of DNA segment would around a protein core of 8 histone molecules. *Most chromatin is loosely packed in the nucleus during interphase and condenses prior to mitosis. In Telophase, DNA uncoils.

Define: Hybridization

*Mating or crossing of 2 true-breeding varieties (purple and white)

Explain why fertilization and meiosis must alternate in all sexual life cycles.

*Meiosis maintains the normal diploid number by halving the number to make the gametes and then allowing the diploid number to be restored through fertilization. *Meiosis makes haploid cells, fertilization makes diploid cells and the cycle continues **TO MAINTAIN CHROMOSOME NUMBER**

Draw the mitotic spindle, including centrosomes, kinetochore, microtubules, non-kinetochore microtubules, asters, and centrioles. Describe how motor proteins associated with the kinetochore microtubules bring about the poleward movement of chromosomes.

*Mitotic spindle: consists of fibers made of microtubules and associated proteins. *Centrosomes: assemble the spindle. Produce microtubules; *Kinetochore: proteins on top of centromeres bind to kinetochore microtubules. *Nonkinetochore microtubules: Overlap and elongate the cell *Centrioles: rod-like bodies that helps develop spindle fibers *When kinetochore microtubules move the separated sister chromatids to opposite ends of the cell, the microtubules shorten by motor proteins in charge of depolymerizing at their kinetochore ends. Kinetochores walk to opposite ends of the cell, they do not pull.

Use the rule of multiplication to calculate the probability that a particular F2 individual will be homozygous recessive or dominant. Given a Mendelian cross, use the rule of addition to calculate the probability that a particular F2 individual will be heterozygous.

*Multiplication states that the probability that 2 or more independent events will occur together is the product of their individual probabilities. *Addition rule states that the probability that any of two or more exclusive events will occur is calculated by adding together their individual probabilities

Distinguish between parental and recombinant phenotypes

*Parental phenotypes: when offspring's phenotype matches parent's *Recombinant phenotypes: Offspring with non-parental phenotypes (new combination of traits) *50% frequency of recombination is observed for any 2 genes on different chromosomes.

Distinguish between the specific and broad interpretations of the terms phenotypes and genotypes

*Phenotypes: Doesn't refer to flower color or any specific physical appearance but the organism's entirety *Genotypes: refers to an organism's entire genetic makeup, not just its alleles for a single genetic locus

Define: True Breeding

*Plants that produce offspring of the same variety when they self-pollinate.

List the phases of mitosis and describe the events characteristics of each phase. Recognize the phases of mitosis from diagrams

*Prophase & Prometaphase: the chromatin condense to form chromosomes, chromosomes condense (now visible), centrosomes migrate to opposite sides of cell, microtubules organize to form spindle (PROPHASE), chromosomes attach via kinetochores and move toward center of cell (PROMETAPHASE), and the nuclear envelope disappears. *Metaphase: the chromosomes line up on equatorial plate and spindle fibers attach to them. *Anaphase: the sister chromatids are pulled apart to opposite poles giving each new daughter cell a copy of the original genome. *Telophase: Spindle breaks down and nuclear envelope reforms, DNA uncoils. *Cytokinesis: Partition of the cytoplasm. Cell divides into 2 separate cells. Occurs by process known as cleavage, forming a cleavage furrow. (Referred to as chromosomes again)

Explain why lethal dominant genes are much rarer than lethal recessive genes. Give an example of a late-acting lethal dominant in humans and explain how it may escape elimination by natural selection (Huntington's disease)

*Rare and arise by mutation in germ cells that produce gametes. Sometimes causes death before allele can be passed on to the next generation. It is very unlikely for this to happen. *Huntington's Disease: no obvious effects until individual is about 35 to 40 years old. Deteriorates the nervous system, once it begins it is irresistible and fatal.

Describe the natural function of restriction enzymes and explain how they are used in recombinant DNA technology.

*Restriction enzymes: recognize specific sequences and cut the DNA molecules at restriction sites. (It's a bacteria's defense mechanism) -Usually makes many cuts, yielding restriction fragments. -They make enzymes that cut foreign DNA and not their own because they label their own DNA with mwthyl groups. *Scientists prepare well-defined segments of DNA in identical copies (DNA cloning). Many bacteria contain plasmids, small circular DNA molecules that replicate separately from the bacterial chromosome. To clone, first must obtain a plasmid and insert DNA from the other sourc (foreign DNA). What results is recombinant DNA.

Define Trisomy:

*Results in 3 copies of a particular chromosome (Down syndrome)

Describe the semiconservative model of replication and the significance of the experiments of Matthew Meselson and Franklin Stahl.

*Semiconservative model of replication: predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or "conserved" from the parent molecule) and one newly made strand. *There were competing models: the conservative model (the two strands rejoin) and the dispersive model (each strand is a mix of old and new) *Experiments by Meselson and Stahl supported the semiconservative model. They labeled the nucleotides of the old strands with a heavy isotope of nitrogen, new nucleotides labeled with a lighter isotope. First replication produced a band of hybrid DNA, eliminating the conservative model. Second replication produced both light and hybrid DNA, eliminating the dispersive model and supporting the semiconservative model.

Distinguish between Somatic cell and gamete:

*Somatic cell: have a diploid number of chromosomes (2n) *Gamete: have a haploid number (n)

Describe the structure and function of telomeres. Explain the possible significance of telomerase in germ cells and cancerous cells.

*Telomeres: Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends. They do not code for anything, are repetitive, and are similar in all chromosomes. They are long strands, but the more replication that occurs, the shorter the strands become. They do not prevent the shortening of DNA molecules, but they do postpone the erosion of genes near the ends of DNA molecules. (protect an organism's genes from being shortened during successive DNa replication). *If chromosomes of germ cells became shorter in every cell cycle, essential genes would eventually be missing from the gametes they produce. Germ cells have enzymes called telomerase that catalyzes the lengthening of telomeres in germ cells. *It does not shoe inappropriate activity in some cancer cells. It's currently under study as a target for cancer therapies. *Telomerase is not active in most human somatic cells.

Explain why Mendel did not find linkage between seed color and flower color, despite the fact that these genes are on the same chromosome.

*The 2 genes were far enough apart and that crossing over would occur so they would assort independently.

Describe the major events of cell division that enable the genome of one cell to be passed on to two daughter cells.

*The S phase ensures that all 46 chromosomes are duplicated for the cell to give to each daughter cell. *G2 phase checks them for error *mitosis happens in which the cell divides to give each daughter cell the same genome. *Reproductive signal: to initiate cell division *Replication: of DNA *Segregation: distribution of the DNA into the new cells *Cytokinesis: separation of the new cells

Describe the role of checkpoints in the cell cycle control system.

*The checkpoints in the cell cycle, ensure that there are no errors or mistakes in each part of the cycle. *Cyclin is a regulatory protein that a kinase much be attached to. The maturation promoting factors give the go ahead signals at the checkpoints after the cell has been checked. *Cyclins and cyclin-dependent kinases are chemicals that allow cell to continue through checkpoints (regulatory proteins). *MPF (maturation-promoting factor) is a cyclin-Ddk complex that triggers a cell's passage past the G2 checkpoint into the M phase.

Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls.

*They ignore checkpoints and signals and keep dividing without any regulation. Because of this an overabundance of cells is created and tumors may appear. *Cancer cells do not respond normally to the body's control mechanisms. Cancer cells may not need growth factors to grow and divide. -They make their own growth factor -may convey a growth factor's signal w/o the presence of the growth factor -They may have an abnormal cell cycle control system

Define: P generation

*True-breeding parents (has a purple flower and a white flower. Dominant: purple, Recessive: white. *First 2 individuals to mate in genetic cross

Define: F2 generation

*When F1 individuals self pollinate or cross pollinate with other F1 hybrids, the F2 generation is produced. Ratio of 3:1 (showed most purple, some white) *Factor for white flowers was not dilluted or destroyed because it reappeared in the F2 generation.

Explain why researchers originally thought protein was the genetic material

*When T.H. Morgan's group showed that genes are located on the chromosomes, the 2 components of chromosomes (DNA and PROTEIN) became candidates for being the genetic material. *Most researchers thought protein was the genetic material because; proteins were macromolecules with great heterogeneity and functional specificity. Little was known about nucleic acids. The physical and chemical properties of DNA seemed too uniform to account for the multitude of inherited traits.

Describe how sex is genetically determined in humans and explain the significance of the SRY gene

*X and a Y chromosomes. XX Female, XY Male *only the ends of the Y chromosome have regions that are homologous with corresponding regions of the X chromosome *The SRY gene on the Y chromosome codes for protein that directs the development of male anatomical features.

Explain why sex-linked diseases are more common in human males. Describe the inheritance patterns and symptoms of color blindness, Duchenne muscular dystrophy, and hemophilia.

*X linked genes follow specific patterns of inheritance. For a recessive x-link to be expressed, a female needs 2 copies of allele (homozygous), and a male needs only one copy of the allele, this is why sex linked disorders are more common in males than females *Color blindness: (mostly x-linked): Males are affected more often than females, because the gene is located on the X chromosome. *Duchenne muscular dystrophy: (affects 1 in every 35oo males,progressive weakening of muscles and loss of coordination) Same as color blindness. *Hemophilia: Common in the monarchies in 1800 because of inbreeding to keep the royal bloodline "pure"

Distinguish between the 3 life cycle patterns characteristic of eukaryotes.

*differ in the timing of meiosis and fertilization *In animals: produce gametes which don't divide before fertilization. Gametes fuse (fertilization) to form a diploid zygote that divides by mitosis to develop into a multicellular organism. (MEIOSIS, FERTILIZATION, MITOSIS) *Plants and Algae: includes a diploid and haploid multicellular stage. Diploid organism (sporophyte) makes haploid spores by meiosis, spores grow by mitosis into haploid organism (gametophyte) which makes haploid gametes by mitosis. Fertilization of gametes results in a diploid organism. Mitosis creates a diploid multicellular organism (Sporophyte). (MEIOSIS, MITOSIS, MITOSIS, FERTILIZATION, MITOSIS) Spores can further divide! *Fungi and some Protists: Only diploid stage is single-celled zygote. No multicellular diploid stage. Zygote produces haploid cells by meiosis. Each haploid cell grows by mitosis into a haploid multicellular organism. Haploid adult produces gametes by mitosis. (MEIOSIS, MITOSIS, MITOSIS, FERTILIZATION) Gametes can no further divide, they only fertilize to become zygotes

Distinguish between Linked genes and sex-linked genes

*linked genes: tend to be inherited together because they are located near each other on the same chromosome. So when crossing over happens, they usually stay together. *Sex-linked genes: Refers to a single gene on a single chromosome. Results in more genetic variation

Explain how a lethal recessive allele can be maintained in a population. Describe the inheritance and expression of cystic fibrosis and sickle-cell disease

*many genetic disorders are inherited recessively, recessive inherited disorders show up only in individuals (homozygous) who inherits one recessive allele from each parents. *Carriers for the recessive allele are heterozygous but it's not likely that the offspring will be homozygous recessive *Consanguineous matings (inbreeding) increases the chance of mating between 2 carriers of the same rare allele. *Cystic fibrosis: allele results in defective or absent chloride transport channels in plasma membranes leading to a buildup of chloride ions outside the cell. Most common lethal genetic disease in US *Sickle-cell disease: caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells (mutation). Cannot bind to oxygen as well as normal blood cells and gets stuck in capillaries. People who are heterozygous experience some symptoms but not as many and are susceptible to malaria.

Explain why Drosophila melanogaster is a good experimental organism for genetic studies

*they breed at high rate, a generation can be bred every 2 weeks, they have only 4 pairs of chromosome

This segment of DNA is cut at restriction sites 1 and 2, which creates restriction fragments A, B, and C. _A_[_______B_______]__C__ Which of the following electrophoretic gels represents the separation of these fragments?

-_B_____C_A__+

Describe 3 events that occur during Meiosis I but not during Mitosis:

1.) Synapsis and crossing over in Prophase I: Homologous chromosomes physically connect and exchange genetic info 2.) There are paired homologous chromosomes (Tetrads) at metaphase plate, instead of individual replicated chromosomes 3.) There are 2 divisions of chromosomes- first in Anaphase I where the homologous chromosomes separate and then in Anaphase II where the sister chromatids separate. Similar because there's only one duplication of chromosomes.

If a segment of DNA (circular or linear) is able to replicate, it must include which of the following?

2. At least one origin of replication

The following 5 strands of DNA are generated during a sequence run. The star at the end indicates a ddNTP. What is the 5' to 3' order of the bases on the template strand? 5'xxxxxA* 5'xxxT 5'xxxxxxG* 5'xxxxC* 5'xxT*

5'xxTTCAG* from shortest to longest 3' AAGTC Complementary base pairs 5' CTGAA Sequencing complementary strand.

Explain in general terms how traits are inherited from parents to offspring.

An organism's traits and appearance are controlled by specific forms of proteins contained in DNA. When gametes are formed, the male and female parents pass along their DNA into their respective gametes. Fertilization fuses the gametes and combines the genetic contribution of each parent into the new offspring.

At the end of DNA replication, but before cell division, the nucleus contains: (G2)

C. Four copies of every gene

Which of the following is true about heterochromatin and not of euchromatin?

E. It remains highly condensed at the G1 phase of the cell cycle.

Explain why it was important that Mendel used large sample sizes in his studies

Mendel used large sample size to get a better idea of the chances of the pea plant offspring having various traits. In other words, he hoped to understand all possible variation in pea plant offspring.

Explain how cell division functions in reproduction, growth, and repair.

Mitosis causes growth and repair by providing more identical cells to replace old, damaged or missing cells for repair or to produce more tissue for growth. It also helps with reproduction by creating haploid cells to form zygotes for reproduction.

Use a punnett square to predict the results of a monohybrid cross, stating the phenotypic and genotypic ratios of the F2 generation

Rr x Rr = RR, Rr, Rr, rr

How do the leading and lagging strands differ?

The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Use a punnett square to predict the results of a dihybrid cross and state the phenotypic and genetic ratios of the F2 generation

YyRr x yyrr = YR x yr, Yr x yr, yR x yr, yr x yr