Biology Exam 3 Study Guide
Biology Exam 3 Study Guide 200001
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This 10 page Study Guide was uploaded by Olivia Sutton on Thursday April 14, 2016. The Study Guide belongs to 200001 at Boston College taught by Danielle Taghian in Spring 2016. Since its upload, it has received 28 views. For similar materials see Molecules and Cells in Biology at Boston College.
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Date Created: 04/14/16
Molecules and Cells (Taghian and Chiles) Exam 3 Study Guide Highlight = Important Principle Highlight = Important Concept Highlight = Key Term Chapter 9: Cellular Respiration and Fermentation (Fermentation Only) Fermentation Metabolic pathway that regenerates NAD+ by oxidizing stockpiles of NADH. Electrons taken from NADH are transferred to pyruvate instead of the Electron Transport Chain o Lactic acid fermentation: pyruvate is converted to lactate; replaces aerobic respiration during intense exercise o Alcohol fermentation: pyruvate is converted into 2 acetylaldehyde (2 carbon dioxides come off; why bread rises in the oven) o Inefficient compared to cellular respiration (produces only 2 molecules of ATP per glucose molecule; cellular respiration produces 29 per glucose molecule!) Test Your Knowledge 1. Which of the following would cause cells to switch from cellular respiration to fermentation? a. The final electron acceptor in the ETC is not available b. The protonmotive force shuts down c. NADH and FADH su2plies are low d. Pyruvate is not available 2. What is the function of the reactions in a fermentation pathway? a. To generate NADH from NADH+ so electrons can be donated to the electron transport chain b. To synthesize pyruvate from lactate c. To generate NAD+ from NADH so glycolysis can continue d. To synthesize electron acceptors so the cellular respiration can continue 3. Why does aerobic respiration produce more ATP than anaerobic respiration? Aerobic respiration utilizes oxygen, which is the normal procedure of cellular respiration. Anaerobic respiration relies on exchanges between NADH and NAD+, which is not enough to sustain the body. 4. What is the difference between Catabolic and Anabolic pathways? a. Catabolic synthesizes larger molecules from smaller components while anabolic is the breakdown of molecules and the production of ATP b. Catabolic needs high energy electrons while anabolic does not c. Catabolic uses carbon containing molecules while anabolic only uses electrons d. Catabolic includes the breakdown of molecules to produce ATP while anabolic synthesizes larger molecules from smaller components Chapter 12: The Cell Cycle The Cell Cycle Responsible for growth, wound repair, and reproduction. Consists of the replication of chromosomes (DNA double helix wrapped around histones in a highly organized manner) o Replication: genome is duplicated. Mechanisms in the nucleus repairs errors in duplication process o Restriction point: ensures that cells are ready to replicate genomes by temporarily blocking the cycle o Mitosis is the production of various cell types while Meiosis is the production of gametes There are five phases of mitosis, where microtubules play a role in moving chromosomes o S phase: part of interphase where replication of genetic material occurs o Cytokinesis: immediately follows telophase; actin microfilaments wrap around circumference of the cell and causing a cleavage furrow (contraction until cells pinch apart Control of the Cell Cycle M PhasePromoting Factor: group of proteins that are active in M phase; they are sufficient by themselves to promote mitosis, are present in all eukaryotes, and are composed of two distinct subunits o Cyclin B: regulatory protein o CyclinDependent Protein Kinase (cdk): catalyzes phosphorylation of a target protein using ATP o Cyclin protein levels oscillate with the cell cycle, increasing in Interphase, peaking in M phase, and decrease afterwards. Cdk1 is active only when bound to Cyclin B; the higher the concentrations of cyclin, the more active MPF is and the more target proteins get phosphorylated (initiating mitosis) Cycle checkpoints prevent the division of cells that are damaged or that have other problems o Social control: cells responding to signals from other cells; cells divide only when their growth benefits the whole organism o Growth factors: polypeptides or small proteins released by cells that stimulate division in other cells o Cancer cells divide without growth. They are not subject to social control at t1 G checkpoint (restriction site is lost) Cancer is a complex family of diseases caused by cells that grow uncontrollably and invade nearby tissues. Cancers have two types of defects: o Proteins required for cell growth are active all the time o Tumor suppressor genes are prevented from shutting down the cell cycle o Most cancers develop after several genes have been damaged. Each type of cancer is caused by a unique combination of errors Rb protein: enforces the G1 checkpoint, keeping the cell in0G . Excessive growth factors can override the inhibitory effects of Rb Cyclin is overproduced, permanently activating Cdk, which continuously phosphorylates its target proteins. P53 protein: transcriptional regulator that’s associated with blocking cell cycle progression and inducing apoptosis in some systems. Test Your Knowledge 1. Which statement about the daughter cells following mitosis and cytokinesis is correct? a. They are genetically different from each other and from the parent cell b. They are genetically identical with each other and with the parent cell c. They are genetically identical with each other but different from the parent cell d. Only one of the two daughter cells is genetically identical with the parent cell 2. After S phase, what compromises a single chromosome? a. Two daughter chromosomes b. A doublestranded DNA molecule c. Two singlestranded molecules of DNA d. Two sister chromatids 3. What major events occur during anaphase of mitosis? a. Chromosomes replicate so each chromosome consists of two identical sister chromatids b. Chromosomes condense and the nuclear envelope disappears c. Sister chromatids separate, and the spindle poles are pushed farther apart d. The chromosomes end up at opposite ends of the cell, and two nuclear envelopes form around them 4. Why are cyclins called cyclins? Explain the relationship to MPF activity Cyclins concentrations oscillate during the cell cycle, peaking at M phase and inducing MPF. Chapter 13: Meiosis Meiosis I Chromosomes that are the same size and shape are called homologous chromosomes (homologs). Homologs carry the same genes, but each one contains different alleles. o Early Prophase I: Chromosomes condense, the nuclear envelope breaks up, and spindle apparatus forms to break chromosomes apart o Late Prophase I: Nonsister chromatids cross over and DNA pieces switch sides o Metaphase I: Tetrads (homologs that have crossed over) line up instead of individually like in mitosis o Anaphase I: Homologs separate and move to opposite sides of the cell o Telophase I and Cytokinesis results in complete cell division Replicated and unreplicated chromosomes are still considered single chromosomes, even though replicated chromosomes have two sister chromatids Ploidy The combination of the number of sets and the haploid number (n). The letter n stands for the number of distinct types of chromosomes in a cell. o Haploid (“singleform”): organisms have cells that contain only one of each type of chromosome. Sex chromosomes are counted as a single type in the haploid number if present. In humans, n is 23. o Diploid (“doubleform”): organisms have two versions (alleles) of each type of chromosome and each gene o The haploid number (n) indicates the number of distinct types of chromosomes present and a cell’s ploidy (2n, 3n, etc.) indicates the number of each type of chromosome preset. The more differences between two genes, the more likely they will cross over. Genes that are close together are considered linked genes o Nondisjunction: failure of homologous chromosomes to separate. Can occurs in as many as 10% of meiotic divisions and causes Down Syndrome. o Aneuploid Zygotes: cells with too few or too many chromosomes that typically do not survive to produce offspring o Trisomy: three copies of one chromosome. Much more common, correlating with the age of the mother and errors in chromosome 21. o Monosomy: one copy of one chromosome Genetic Variation At a chiasma, the nonsister chromatids from each homolog have been physically broken at the same point and attached to each other. Chromosomes are exchanged. o Each daughter cell gets a random assortment of maternal and paternal chromosomes. o Crossing over produces new combinations of alleles within a chromosome. Test Your Knowledge 1. What are homologous chromosomes? a. Chromosomes that are similar in their size, shape, and gene content b. Similar chromosomes that are found in different individuals of the same species c. The two “threads” in a replicated chromosome (they are identical copies) d. The products of crossing over, which contain a combination of segments from maternal chromosomes and segments from paternal chromosomes 2. Explain the relationship between homologous chromosomes and sister chromatids Homologous chromosomes are comprised of sister chromatids, which contributes to the fact that homologous chromosomes are so similar with each other. 3. Meiosis II is similar to ______ Mitosis 4. What is an outcome of genetic recombination? a. The synapsing of homologs during prophase and meiosis I b. The new combination of maternal and paternal chromosome segments that results when homologs cross over c. The new combinations of chromosomes segments that result when self fertilization occurs d. The combination of a haploid phase and a diploid phase in a life cycle Chapter 14: Mendel and the Gene Mendel’s Studies Mendel experimented with garden pease after becoming interested in inheritance in 1865 o Trait: any characteristic of an individual o Phenotype: individual’s observable features o The Monohybrid Cross: differing in only one trait (in Mendel’s experiments, round seeds vs. wrinkled seeds) o Dominant: observed phenotype in individuals carrying both genetic determinants o Recessive: hidden phenotype o Reciprocal Cross: it does not matter whether the genetic determinants are located in the male or female parent, as long as they are on autosomes In Genetic Notational Convention, homozygous individuals have two copies of the same allele (RR, rr) while heterozygous individuals have different alleles (Rr). Pure lines are homozygous and offspring of heterozygotes express a dominant phenotype. Genes/Alleles/Genotypes Genetic determinants act like discrete particles/units o Genotype: all alleles present in one individual. Influences the expression of phenotypes in the individual o Dihybrid cross: parents mate with two different traits. Predicts 9 different offspring genotypes with 4 phenotypes (punnett squares; 9:3:3:1) SexLinked Traits Thomas Hunt Morgan’s Fly experiments revealed a relationship between the gender of the parent and inheritance, using fruit flies. o Sex chromosomes: X and Y chromosomes, determine the gender of the offspring (XX = female, XY = males) o Autosomes: all other chromosomes o Sex chromosomes pair during Meiosis I and segregate during Meiosis II Morgan proposed that the X chromosome carried the gene for eye color in fruit while the Y chromosome did not. Xlinked inheritance means that females would have two copies of a certain gene while males only have one. This applies to inheriting colorblindness, which is an Xlinked recessive genetic disorder that affects 7% males and 0.4% females Gene Linkage Linked genes are always transmitted together during gamete formation (unless crossing over occurs), violating the principle of independent assortment o Linkage: the physical association of 2 or more genes found on the same chromosome o SexDetermining Region of the Y Chromosome (SRY gene): in the 7 th week of development, it activates a number of genes and gonads develop testes. This only happens in males. Inappropriate crossing over can result in exchange of the SRY gene region onto the X, resulting in sex reversal Incomplete Dominance and Codominance Incomplete dominance: alleles of a gene are not always clearly dominant or recessive. Heterozygotes can have an intermediate phenotype Codominance: A heterozygote organism can display the phenotype of both alleles of a single gene. Neither allele is dominant or recessive Blood types in humans exhibit Codominance o A: glycoprotein “A” on plasma o B: glycoprotein “B” on plasma o AB: contains both “A” and “B” o O: lacks both “A” and “B” The Law of Segregation The chromosome theory of inheritance states that chromosomes are composed of Mendel’s hereditary determinants (genes) o Pedigrees: family trees; used to analyze the human crosses that already exist o Carriers: have the allele and transmit it without exhibiting the phenotype Recessive phenotypes only show up when both parents have the allele and pass it on to their offspring When a phenotype is due to an autosomal recessive gene, then individuals with the trait must be homozygous Autosomal dominant traits are expressed in any individual with at least one dominant allele If the trait appears equally often in males AND females, its autosomal If males are more likely to have the trait, then its Xlinked Xlinked Traits Recessive traits usually skip generations in a pedigree Dominant traits rarely skip generations and are indicated when an affected male had all affected daughters, but no affected sons Test Your Knowledge 1. Why is the allele for wrinkled seed shape in garden peas considered recessive? a. It “recedes” in the F2 generation when homozygous parents are crossed b. The trait associated with the allele is not expressed in heterozygotes c. Individuals with the allele have lower fitness than that of individuals with the dominant allele d. The allele is less common than the dominant allele (the wrinkled allele is a rare mutant) 2. The alleles found in haploid organisms cannot be dominant or recessive. Why? a. Dominance and recessiveness describe which allele is expressed in phenotype when different alleles occur in the same individual b. Because only one allele is present, alleles in haploid organisms are always dominant c. Alleles in haploid individuals are transmitted like mitochondrial DNA or chloroplast DNA d. Most haploid individuals are bacteria, and bacterial genetics is completely different from eukaryotic genetics 3. Why can you infer that individuals that are “pure line” are homozygous for the gene in question? a. Because they are highly inbred b. Because only two alleles are present at each gene in the populations to which these individuals belong c. Because in a pure line, phenotypes are not affected by environmental conditions or gene interactions d. Because no other phenotype is ever observed in a pure line population, this implies that only one allele is present 4. What is meant by the claim that Mendel worked with the simplest possible genetic system? a. Discrete traits, two alleles, simple dominance and recessiveness, no sex chromosomes, and unlinked genes are the simplest situation known b. The ability to selffertilize or crosspollinate made it simple for Mendel to set up controlled crosses c. Mendel was aware of meiosis and the chromosome theory of inheritance, so it was easy to reach the conclusions he did d. Mendel’s experiment designs and his rules of inheritance are actually neither complex or sophisticated
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