BIO-120 - Unit 3 Study Guide.docx

**[LIFE 120 -- Unit 3 Study Guide]** **Chapter 9 -- Cell Cycle** 1. Describe the various purposes of cell division. - Allows cell to produce more if its own. - Organism reproduction. - Supports continuity of life. - Tissue growth, muscle growth, etc. 2. Define and distinguish the fo...

**[LIFE 120 -- Unit 3 Study Guide]** **Chapter 9 -- Cell Cycle** 1. Describe the various purposes of cell division. - Allows cell to produce more if its own. - Organism reproduction. - Supports continuity of life. - Tissue growth, muscle growth, etc. 2. Define and distinguish the following terms: genome, chromosome, chromatin, homologous chromosomes, duplicated chromosome, sister chromatids, centromere. Genome: all of a cell's genetic information (DNA). Chromosome: a long strand of DNA double helix wrapped around protein (consists of DNA and proteins). Chromatin: the entire complex of DNA and proteins that is the building material of chromosomes. Homologous Chromosomes: a pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci (one homologous chromosome is inherited from the father, the other from the mother). Duplicated Chromosome: a replicated chromosome that contains two identical copies of the same information. Sister Chromatids: joined copies of the original chromosome. Centromere: the region on each sister chromatid where it is most closely attached to its sister chromatid by proteins. 3. Describe the DNA content and ploidy of human somatic and germ cells. Somatic Cells: cells that do not give rise to offspring (ex; skin cells, brain cells, muscle cells)- contain 46 chromosomes, 23 homologous pairs. Germ Cells (Gametes): cells that give rise to offspring (ex; sperm and eggs)- contain 23 chromosomes, one from each homologous pair of chromosomes. 4. Describe the events that occur and the DNA content of the cell during each phase of the cell cycle. Interphase: makes up roughly 90% of the cell cycle (divided into sub-phases/the cell grows during each subphase, DNA is duplicated). Prophase: chromosomes condense, and duplicated chromosomes appear as sister chromatids (the mitotic spindle begins to form, and the centromeres begin to move away from each other). Prometaphase: the nuclear envelope begins to fragment (microtubules "invade" nuclear area and attach to chromatids via kinetochores/chromosomes pulled "back and forth" by microtubules. Metaphase: centrosomes are located at opposite poles (chromosomes align at the center of the cell along the metaphase plate/kinetochores of sister chromatids are attached to microtubules from opposite poles). Anaphase: sister chromatids separate and are pulled towards opposite poles (two ends of the cell gain full sets of chromosomes). Telophase: nuclear envelope reforms around chromosomes (chromosomes become less condensed). Cytokinesis: Cell membrane pinches off leaving us with two identical cells. 5. Design an experiment to determine the length of each phase of the cell cycle. Set a timer over the course of 24 hours and create a time lapse showing when and where the cell goes through the different phases. - Label parts of the cell beforehand. 6. List the phases of mitosis in the correct temporal order. Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase, Cytokinesis. 7. Describe the major events that occur during each phase of mitosis, particularly with regards to spindle formation and chromosome movements. Interphase: chromosomes duplicate. Prophase: chromosomes condense in the center of the cell. Mitotic spindle begins to form, and centrosomes move away from each other. Prometaphase: chromosomes pulled "back and forth" by microtubules that have formed from the centrosomes. Metaphase: chromosomes align along the center of cell at the metaphase plate. The centrosomes have reached opposite poles. Anaphase: sister chromatids separate and move towards opposite ends of the cell. Two ends of the cell contain full sets of chromosomes. Telophase: chromosomes become less condensed. Spindle depolymerizes. Cytokinesis: each new set of DNA is surrounded by a new nuclear envelope. Cell splits into two, each with identical sets of DNA. 8. Describe the structure of microtubules, how they are formed, and how they shrink. Microtubules are narrow tubes comprised of tubulin proteins. - Microtubules are oriented- plus end and minus end. - Microtubules are dynamic- grow by adding tubulin to the plus end- shrink by losing tubulin from the minus end. Microtubule length is dictated by the addition and subtraction of subunits from each end. - Microtubules reorganize to form the mitotic spindle and segregate chromosomes. - There are two microtubule motor proteins. Dynein: moves toward the minus end. Kinesin: moves toward the plus end. 9. Understand the relationship between motor protein activity and microtubule movement. Motor proteins help the pull apart of chromosomes during anaphase by walking along the microtubules. They can do one of three things: 1. Chromosomes could be "walked in" by the motor that anchor themselves to the chromosome. 2. Chromosomes could be reeled in by the motors that anchor themselves to the centrosome. 3. Chromosomes could be walked in and reeled in at the same time. 10. Predict the results of a microtubule photobleaching experiment based on different modes of chromosome movement. 1. Microtubules are coupled to a fluorescent marker. 2. A region of the microtubule is photobleached. - What will happen to the fluorescent and bleached regions of the microtubules if chromosomes are both "reeled in" and "walked in" by motor proteins? - The region to the left of the bleached area will shorten. - The bleached region will move to the left. - The region to the right of the bleached area will shorten. 11. Describe actin and myosin proteins support the formation and contraction of the cleavage furrow. 1. Actin forms long filaments. 2. Antiparallel myosin motors move these filaments. 3. Actin-myosin complexes make up contractile ring. 4. Myosin activity causes ring to contract, form cleavage furrow. 12. Distinguish differences in bacterial cell division from eukaryotic cell division. Prokaryotes (bacteria and archaea): reproduce by a type ofc ell division called binary fission. - In E. coli, the single chromosome replicates, beginning at the origin of the replication. - The two daughter chromosomes actively move apart while the cell elongates. - The plasma membrane pinches inward, dividing the cell. Eukaryotic cells go through mitosis or meiosis. 13. Cite reasons for why cell division needs to be regulated, mechanisms for how cell division is regulated, and consequences if cell division goes unregulated. Cell division needs to be regulated so that we can help ensure that cell division happens successfully; and so that way cells don't divide uncontrollably. - Cancer results from the uncontrollable division of cells. - Cell division is regulated through a series of checkpoints where various signals determine whether a cell can proceed through the cell cycle. - If cell division goes unregulated, one can develop cancer. **Chapter 10 -- Meiosis** 1. Identify organismal characteristics that are influenced by genetics versus characteristics that are also shaped by environmental conditions. - Organisms pass genetic blueprints from one generation to the next. - Offspring tend to resemble their parents due to genetic factors. Characteristics influenced by genetics = skin color, eye color, face shape, hair color, etc. Characteristics shaped by environmental conditions = skin type, amount of melanin, ability to stand certain temperatures, diseases, etc. Heredity = the transmission of traits from one generation to the next. Variation = demonstrated by the differences in appearance that offspring show from parents and siblings. 2. Define the terms gene and allele and describe what these terms refer to within DNA. Gene: units of heredity, refer to a particular region of DNA. Allele: variants of a given gene, due to slight differences in DNA sequence. 3. Describe how different alleles lead to different traits. Alleles: variants of a given gene, due to slight differences in the DNA sequence. - Ex; you may have the gene for soft hair, but your hair is brown, black, or blonde. - Alleles are found on the same spot, but code for different variants of that gene. 4. Distinguish between homologous chromosomes, duplicated chromosomes, chromatids, and sister chromatids, and apply these terms within the context of mitosis and meiosis. Homologous Chromosomes: are the same size. - Show the same banding pattern. - Have the same genes at the same loci. - May have different alleles at a given loci. - DNA sequences are nearly identical but have important differences giving rise to different alleles. Duplicated Chromosomes: completely identical to each other (copies of the same book). Chromatids: one single chromosome of the duplicated chromosomes. Sister Chromatids: the two identical chromatids. In Mitosis: homologous chromosomes make duplicated chromosomes, then the chromatids split and go towards opposite ends. In Meiosis: homologous chromosomes split in the first anaphase, then sister chromatids split in the second anaphase. 5. Describe the sex chromosome system for humans. Sex Chromosomes: determine the sex of the organism. - Humans have X and Y chromosomes. - Genetic females have homologous pair of X chromosomes (XX). - Genetic males have one X and one Y chromosome (XY). - The remaining 22 pairs of chromosomes are called autosomes. 6. Describe differences in the chromosome content of somatic and germ line cells. Somatic Cells: do not give rise to reproductive cells. - Have 46 total chromosomes. - Two sets of 23 homologous chromosomes. - One set from mother, one set from father. - Each pair of homologous chromosomes includes one chromosome from each parent. Gametes: produced by germ cells located in reproductive organs (ovaries and testes), involved in reproduction. - It has 23 total chromosomes. - One complete set of chromosomes. - Each chromosome is either maternally or paternally derived. 7. Apply the concept of ploidy to describe cells as they progress through cell division. Ploidy: number of sets of chromosomes. - N = number of chromosomes in single set. - Humans: n = 23 chromosomes. Diploid: having two sets of chromosomes. - Human somatic cell: 2n = 46. Haploid: having one set of chromosomes. - Human gametes: 1n = 23. 8. Draw a diagram depicting the steps that occur during the human life cycle and indicate the ploidy of cells at different phases of this life cycle. 9. Draw a diagram depicting the steps that occur during an alteration of generations life cycle and indicate the ploidy of cells at different phases of this life cycle. 10. List the phases of meiosis in proper order and describe the movement of chromosomes that occurs at each phase. Meiosis Phases: meiosis 1 separates homologs and meiosis 2 separates sister chromatids. - Prophase 1: chromosomes condense, and each chromosome pairs up with its homolog. - Metaphase 1: pairs of homologous chromosomes line up at the metaphase plate with one chromosome of each pair facing each pole. - Anaphase 1: homologs move toward opposite poles, guided by spindle apparatus. - Telophase/Cytokinesis: when telophase 1 begins, each half of the cell has a complete haploid set of duplicated chromosomes. Each chromosome is composed of 2 sister chromatids. Cytokinesis forms two haploid cells. - Prophase 2: chromosomes, each still composed of two chromatids associated at the centromere, are moved by microtubules toward the metaphase 2 plate. - Metaphase 2: chromosomes are positioned at the metaphase 2 plate. - Anaphase 2: sister chromatids separate towards opposite poles as individual chromosomes. - Telophase/Cytokinesis: nuclei form, chromosomes begin decondensing. Cytokinesis produces four daughter cells each with a haploid set of chromosomes. 11. Compare and contrast the events of mitosis with that of meiosis I and meiosis II, particularly with regards to the pairing and separation of chromosomes and the overall ploidy of each cell. Mitosis: chromosomes duplicate, then separate producing two identical cells with a diploid number of cells. Meiosis: chromosomes duplicate, separate into two haploid gametes, then separate again into four daughter cells each with a haploid number of chromosomes. 12. Draw and label a picture of a homologous chromosome pair as it moves through mitosis vs meiosis. 13. Describe how an error in chromosome separation could lead to an offspring with an extra copy of a chromosome or an offspring lacking a copy of a chromosome. There could be an error in anaphase. 1. Homologous chromosomes fail to separate causing there to be only one gamete still with a diploid number of chromosomes. - There could be an error in anaphase. 2. Chromatids fail to separate into four daughter cells. 14. Describe how the independent assortment of chromosomes produces gamete diversity. Homologous pairs of chromosomes orient randomly at metaphase I of meiosis. - In independent assortment, each pair of chromosomes sorts maternal and paternal homologs into daughter cells independently of the other pairs. - The number of combinations possible when chromosomes assort independently into gametes is 2n, where n is the haploid number. - For humans (n=23), there are more than 8 million (223) possible combinations of chromosomes for gametes. 15. Describe where and when in meiosis crossing over occurs and which structures participate in information exchange. Crossing over occurs between prophase I and metaphase I and is the process where two homologous chromosome non-sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosome sister chromatids. 16. Describe how random fertilization increases the variation present within a population. Random fertilization adds to genetic variation because any sperm can fuse with any ovum (unfertilized egg). - The fusion of two gametes (each with 8.4 million possible chromosome combinations from independent assortment) produces a zygote with any of about 70 trillion diploid combinations. **Chapter 11 -- Genetics** 1. Distinguish between a genetic character and trait. Character: a heritable feature that varies among individuals (ex; flower color, height). Trait: a variant of a particular character (ex; purple flowers, tall height). 2. Distinguish between the blending hypothesis and the particulate hypothesis. Describe how Mendel's experiments supported the particulate hypothesis. Blending Hypothesis: initial ideas on genetic inheritance were that genetic material tended to blend during successive generations. - Ex; a tall and short parent produces medium sized offspring. Particulate Hypothesis: parents pass on discrete heritable units (genes) that remain intact across generations. - Ex; brown eyed parents produce brown and blue-eyed offspring. 3. Explain why model organisms can be used to derive insights into human biology as well as benefits and limitations of using model organisms. Model Organisms: a non-human species that is studied to understand basic biological processes. - Ex; rats, mice, fruit flies, worms, frogs, fish, etc. 4. Cite particular benefits of using snow peas for genetic experiments. Benefit of Snow Peas: they have many characters with different traits that are visually discernable. - Ex; flower color -- purple vs white. - They can be grown in large enough numbers so that overall patterns can be determined by statistics. - Matings can be controlled between plants. 5. Describe how controlled matings can be done in snow peas. Snow peas normally self-fertilize. Controlled Matings: 1. Remove stamens from purple flowers. 2. Transfer sperm-bearing pollen from stamens of another flower. 3. Pollinated carpel matures into a pea pod. 4. Plant seeds from a pod. 5. Offspring develops. 6. Use genetic terminology to describe Mendel's mating strategy. Used plants that were true breeding for many generations. - True breeding plants produce offspring with the same trait when they self-pollinate. - Tracked plants through three different generations. Cross 1: Mendel mated two contrasting, true-breeding plants, a process called hybridization. - The true-breeding parents are the P generation. - Hybrid offspring of the P generation are called the F1 generation. Cross 2: Mendel allowed F1 individuals to self-pollinate or cross-pollinate with other F1 hybrids. - Offspring of the F1 generation are called the F2 generation. 7. Apply the four components of Mendel's model of genetic inheritance to a particular cross. 1. Alternative versions of genes account for variations in inherited characters. - Ex; the gene for flower color in pea plants exists in two versions, one for purple flowers and one for white flowers. - These alternative versions of a gene are now called alleles. - Each gene resides at a specific locus on a chromosome. 2. For each character, an organism inherits two alleles, one from each parent. - Mendel made this deduction without knowing about the existence of chromosomes. - Two alleles at a particular locus may be identical, as in the true-breeding plants of Mendel's P generation. - Alternatively, the two alleles at a locus may differ, as in the F1 hybrids. 3. If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance. - In the flower-color example, the F1 plants had purple flowers because the allele for that trait is dominant. 4. The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes. - This is now known as the law of segregation. - Thus, an egg or a sperm gets only one of the two alleles that are present in the organism. - This segregation of alleles corresponds to the distribution of homologs to different gametes in meiosis. 8. Apply the four components of Mendel's model of genetic inheritance to the process of meiosis. 1. Alternative versions of genes account for variations in inherited characters. - Ex; the gene for flower color in pea plants exists in two versions, one for purple flowers and one for white flowers. - These alternative versions of a gene are now called alleles. - Each gene resides at a specific locus on a chromosome. 2. For each character, an organism inherits two alleles, one from each parent. - Mendel made this deduction without knowing about the existence of chromosomes, - Two alleles at a particular locus may be identical, as in the true-breeding plants of Mendel's P generation. - Alternatively, the two alleles at a locus may differ, as in the F1 hybrids. 3. If the two alleles at a locus differ, then one (the dominant allele) determines the organism's appearance, and the other (the recessive allele) has no noticeable effect on appearance. - In the flower-color example, the F1 plants had purple flowers because the allele for the trait is dominant. 4. The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes. - This is now known as the law of segregation. - Thus, an egg or a sperm gets only one of the two alleles that are present in the organism. - This segregation of alleles corresponds to the distribution of homologs to different gametes in meiosis. 9. Define genotype, phenotype, homozygous, and heterozygous. Genotype: an organism's genetic makeup. Phenotype: an organism's physical appearance. Homozygous: having two identical alleles for a gene. Heterozygous: having two different alleles for a gene. 10. Describe how an organism's genotype leads to its phenotype. Yellow (Y) Green (y) Round (R) Wrinkled (r) Yy, YY = Yellow yy = green RR, Rr = round rr = wrinkled 11. Use a Punnett square to identify offspring proportions for a particular pair of organisms. Punnett squares show potential offspring. - Different possible gametes are placed on each axis. - Potential fertilization events are represented by gamete combinations in the center squares. 12. Describe how a testcross can be used to infer the genotype of an organism that expresses the dominant phenotype. The testcross is used to determine genotype of individual with dominant phenotype. - Cross with a homozygous recessive individual. - If any offspring display the recessive phenotype, then the original must have been heterozygous. 13. Predict genotype and phenotype ratios resulting from a dihybrid cross for genes located on the same chromosome and genes located on different chromosomes. When performing a dihybrid cross with genes located on different chromosomes, the expected phenotypic ratio is typically 9: 3: 3: 1. 14. Describe how independent assortment of chromosomes can produce offspring in the F2 generation of a dihybrid cross that have recombinant phenotypes. The result of Mendel's dihybrid experiments is the basis for the law of independent assortment. - It states that each pair of alleles segregates independently of each other pair of alleles during gamete formation. - This law applies to genes on different chromosomes or those far apart on the same chromosome. - Genes located near each other on the same chromosome tend to be inherited together. 15. Describe how recombination can produce offspring in the F2 generation of a dihybrid cross that have recombinant phenotypes. Sometimes when genes are in the same chromosome, crossing over will happen between them. - They will then end up being on different chromosomes after all. - That leads to them acting just like genes in separate chromosomes. 16. Compare the rates at which genes located close together on the same chromosome, far apart on the same chromosome, or on different chromosomes will produce offspring in the F2 generation of a dihybrid cross that have recombinant phenotypes. If genes are located further apart on the same chromosome, there is a greater chance that there will be a crossover between them. 17. Apply the multiplication and addition rules to calculate probabilities, including the probabilities of producing certain offspring because of a genetic cross. Multiplication Rule: the probability that 2 events will both happen together is the multiplication of the probability that those events will happen individually. - You figure out the probability of each event happening and then multiply them. - Ex; the chance you will get heads 3 times in a row (½) Addition Rule: the probability that an event that is mutually exclusive from each other will happen. - You figure out the chance of that even happening and then add them together. - Ex; chance you will get heads, heads, tails (1/8 + 1/8 + 1/8 = 3/8) 18. Define, provide examples, and conduct crosses for complex genetic inheritance patterns, including incomplete dominance, codominance, multiple alleles, and polygenic inheritance. Complete Dominance: a cell that has a genotype that is heterozygous or homozygous dominant will have the same phenotype. - Ex; whole Mendel's research. Incomplete Dominance: a cell with a heterozygous genotype will have a phenotype that is a mixture of the two homozygous phenotypes. - Ex; CC is a red flower; cc is a white flower. - The Cc flower will be pink. Codominance: 2 genes affect the same trait. - Ex; cows. - RR cows are red; WW cows are white. - RW cows are spotted. Multiple Alleles: more than two possible versions, more than multiple alleles. - Ex; blood type: Ia, Ib, or ii are the genotypes and they could make the phenotypes of A, B, AB, and O. - Therefore, Ia and Ib are codominant and i is recessive. Pleiotropy: one gene controls multiple characters. - Ex; sickle-cell disease. Polygenic Inheritance: many genes control one character. - Makes quantitative characters: the character varies in a continuum way. - You can use the probability rules. - Ex; skin color, height. 19. Interpret the basic features of a pedigree and infer a disease inheritance pattern from a diseased family. Humans genetic research has certain limitations: - Generation time is long, parents produce relatively few offspring, controlled breeding is not feasible. - A pedigree is a family tree describing the relationships of parents and children across generations. Pedigrees can help determine: 1. If a disease has dominant or recessive inheritance. 2. If certain individuals are carriers of a disease allele. - Carrier: heterozygous for the disease allele but does not show the disease phenotype. 3. The probability of offspring inheriting disease alleles. **Chapter 12 -- Chromosomes** 1. Explain characteristics of recessive and dominant disease alleles that would allow them to remain in a population over many generations. Recessive disorders only show up if the child is homozygous recessive and both parents must have been carriers. - This usually does not happen because if the disease is rare there is a low chance that two carriers will breed and have the 25% chance offspring that is homozygous recessive. - Some diseases are more apparent in certain populations because they breed with each other. Why don't diseases go away after a while? - Arise through random mutations in the gametes (it just happens, you have no choice). - Disease allele does not affect a person's ability to have children (you can still have kids/ex; dwarfs and Huntington's disease). - Does affect reproduction but has an advantage in other areas (ex; sickle-cell disease). 2. Describe how the sickle cell disease mutation gives rise to irregularly shaped blood cells. Sickle Cell Disease: a hereditary disorder characterized by production of abnormal hemoglobin proteins. - A mutation within the gene that encodes hemoglobin leads to a change in polypeptide sequence and clumping of hemoglobin proteins. - Clumping of hemoglobin causes red blood cells to form a sickle shape. - Sickle-shaped blood cells are less able to pass through small blood capillaries. 3. Describe the different phenotypes that can result from sickle cell genotypes. Homozygous Recessive: have abnormal hemoglobin that aggregates individuals affected by the disease, symptoms include anemia and other problems associated with restricted blood flow. - Recessive carrier: sometimes called sickle cell trait, they have enough normal hemoglobin that their red blood cells do not sickle, these individuals are phenotypically normal. - At low oxygen concentrations, hemoglobin tends to aggregate and cause red blood cells to sickle. 4. Provide a reasonable hypothesis for why the sickle cell allele occurs more commonly in populations that are exposed to malaria. Sickle cell allele occurs more commonly in populations that are exposed to malaria because malaria involves a parasite that affects the red blood cells; so those that are being expose to malaria are already at risk of having their red blood cells damaged which is what sickle cell further does. 5. Explain how consanguineous mating can increase the likelihood of an individual being born with a rare recessive condition. Consanguineous Matings: matings between individuals who are closely related can increase the likelihood of a person being homozygous for a rare recessive disease allele. - Hemophilia, a blood clotting disorder, is relatively rate within the general population. - It is unlikely that a person will be homozygous for the disease allele. - However, the disease allele was common within European royalty, and matings between relatives were also common. - Thus, a disproportionately high number of royal children were born with the disease. 6. Describe the process of X-inactivation and predict the phenotypes that will result for X-linked recessive traits because of X-inactivation in females. In mammalian females, one of the two X chromosomes in each cell is randomly inactivated during embryonic development. - The inactive X condenses into a Barr body. - If a female is heterozygous for a particular gene located on the X chromosome, she will display a mosaic phenotype for that character. 7. Predict the genotype ratios that will result from a cross with linked versus unlinked genes. Linked genes tend to produce parental phenotypes. - Genes on different chromosomes ratio = 1: 1 : 1 : 1. - Genes on the same chromosomes ratio = 1: 1: 0: 0. 8. Describe how the frequency of recombinant phenotypes can be used to estimate the distance between two linked genes. The lower the recombination frequency, the closer the linked genes are. - 50% is the highest recombination frequency two chromosomes can have. - Usually that means they're on a different chromosome.