bio 2, exam 1 week 3 connections – Flashcards
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Random orientation of homologous chromosomes occurs in ________ of meiosis. prophase II metaphase II anaphase I prophase I metaphase I
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Metaphase I
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Consider a cell that has four pairs of chromosomes. What is the number of possible chromosome orientations in that cell? 32 24 8 4 16
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16
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Consider a cell that has three pairs of chromosomes. What fraction of the gametes produced from this cell will contain only maternal chromosomes? 1/12 1/2 1/8 1/4 1/6
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1/8
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Random orientation of chromosomes during meiosis increases the amount of variation in the next generation. What other process during meiosis leads to an increase in variation in the next generation? Crossing over between homologous chromosomes. All of these lead to increased variation in the next generation. Attachment of the spindle fibers to homologous chromosomes. The formation of 4 haploid daughter cells. Two distinct phases, meiosis I and meiosis II.
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Crossing over between homologous chromosomes.
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Consider a cell that has a diploid chromosome number of 10 (2N=10). How many possible gametes can this cell produce? 16 100 1024 10 32
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32 (2^n)
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In a human somatic cell (normal body cell) that is in G1, what would be true about chromosome number and structure? Check all that apply. These cells would be considered haploid (n). These cells would be considered diploid (2n). These cells would be considered tetraploid (4n). These cells would contain homologous chromosomes. These cells would contain sister chromatids. These cells would contain condensed chromosomes.
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These cells would be considered diploid (2n). These cells would contain homologous chromosomes.
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As the hamster cell replicates, what structures condense and line up on the cell's equator? chromosomes centrioles centromeres spindles
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chromosomes
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What happens immediately after the chromosomes line up on the cell's equator? The nucleolus reappears in the two new daughter cells. Chromosomes separate and move to opposite ends of the cell. The microtubules of the mitotic spindle disintegrate. Homologous chromosomes pair and begin a second round of cell division.
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Chromosomes separate and move to opposite ends of the cell.
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What is the most likely reason that chromosomes must line up on the cell equator before being divided and moving to the opposite sides of the cell? to stabilize the hamster cell so that it will not rupture to allow the nucleolus to rematerialize in the periphery of the cytoplasm to enable the microtubules to attach to the kinetochores properly so chromosomes can be separated into chromatids for equal genetic distribution
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to enable the microtubules to attach to the kinetochores properly
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The body cells of hamsters have 44 chromosomes. After mitosis and cell division, how many chromosomes should each hamster cell have? 11 22 44 88
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44
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what phase of mitosis take the longest? anaphase prophase metaphase telophase
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prophase
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The spindle apparatus is fully formed by the end of metaphase II. anaphase II. prometaphase II. telophase II. prophase II.
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prometaphase II.
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Separation of ________ occurs in anaphase II of meiosis. the two nuclei homologous chromosomes non-homologous chromosomes cytoplasm sister chromatids
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sister chromatids
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At the end of meiosis II, there are four haploid cells, with each chromosome containing two sister chromatids. two haploid cells, with each chromosome containing two sister chromatids. four haploid cells, with each chromosome consisting of a single chromatid. two haploid cells, with each chromosome consisting of a single chromatid. four diploid cells, with each chromosome consisting of a single chromatid.
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four haploid cells, with each chromosome consisting of a single chromatid.
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Why are two phases of meiosis necessary? In order to produce 4 gametes. In order to maximize variation in the next generation. In order to both reduce the chromosome number and separate sister chromatids. In order to produce two daughter cells. All of these.
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In order to both reduce the chromosome number and separate sister chromatids.
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When do sister chromatids differ Meiosis II separates sister chromatids. What might make sister chromatids differ from each other? If sister chromatids were recombined during crossing over. If sister chromatids come from different homologous chromosomes. If sister chromatids were heterozygous. None of these, sister chromatids will always be identical. If sister chromatids were randomly assorted during meiosis I.
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If sister chromatids were recombined during crossing over.
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If sister chromatids failed to separate during meiosis II, what would the resulting gametes look like? 2 gametes will be normal and 2 gametes will have 2 of the effected chromosomes chromosomes. 2 gametes will be normal and 2 gametes will have 0 of the effected chromosomes chromosomes. 2 gametes will be normal, 1 gamete will have 2 of the effected chromosomes, and 1 gamete will have 0 of the effected chromosomes. None of the gametes will have any of the effected chromosomes. 2 gametes will have 2 of the effected chromosomes and 2 gametes will have 0 of the effected chromosomes.
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2 gametes will be normal, 1 gamete will have 2 of the effected chromosomes, and 1 gamete will have 0 of the effected chromosomes.
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A cell biologist examines a diploid cell from a barley plant during prometaphase of mitosis and determines that 28 chromatids are present. The role of meiosis in this plant is to (Check all that apply) increase the number of chromosomes per cell from 14 to 28. produce 4 daughter cells that are genetically identical to each other. reduce the number of chromosomes per cell from 28 to 14. reduce the number of chromosomes per cell from 14 to 7. produce 4 daughter cells that are genetically identical to the parental cell.
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produce 4 daughter cells that are genetically identical to each other. reduce the number of chromosomes per cell from 14 to 7.
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The success of DNA replication is assessed during the ______ phase. G2 G1 M C S
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G2
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A eukaryotic cell that receives a "go-ahead" signal at the G1 checkpoint of the cell cycle will enter a resting stage. stop growing. move directly into the G2 phase. move directly into the M phase. complete the cycle and divide.
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complete the cycle and divide.
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DNA repair enzymes will probably be the most highly active during what phase of the cell cycle? G2 G1, G2, and cytokinesis G1 and G2 Cytokinesis G1
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G2
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A cell has a mutation that prevents cytokinesis from occurring. What is the most likely consequence of this mutation There will be no effect, because cytokinesis is not part of mitosis. The nuclear material will divide but the cell will not, resulting in a cell with multiple nuclei. The cell will be unable to replicate its DNA and divide; it will remain in the G1 phase. Both the nucleus and the cell will divide, but the resulting daughter cells will be misshapen and nonviable. The cell will be able to divide by meiosis but not by mitosis.
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The nuclear material will divide but the cell will not, resulting in a cell with multiple nuclei.
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A geneticist examines the karyotype of a diploid cell from a particular species of frog and determines that 12 chromosomes are present. If a germ-line cell from this species divides by meiosis, then at the end of meiosis I each cell will have (Check all that apply.) 12 centromeres 12 chromatids 6 chromosomes 6 chromatids
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12 chromatids 6 chromosomes
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The cell cycle is regulated by checkpoints during the _______ phases. G1, S and G2 G1, S, G2 and M G1, G2, and M G1, S and M G1, S and C
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G1, G2, and M
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Which of the following events do NOT occur in prophase of mitosis? nuclear membrane breaks down DNA condenses to form chromosomes nucleolus breaks down chromosomes are replicated mitotic spindle begins to form
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chromosomes are replicated
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Which of the following statements about microtubules during anaphase is TRUE? Those attached to chromosomes shorten, while those that are unattached elongate. Both attached and unattached microtubules elongate. Those attached to chromosomes elongate, while those that are unattached shorten. Both attached and unattached microtubules shorten. Both attached and unattached microtubules elongate at first and then shorten.
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Those attached to chromosomes shorten, while those that are unattached elongate.
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Why do chromosomes condense during prophase? All of these are TRUE. So that they will not be damaged when they are moved around the cell. So that kinetochore proteins will attach to them. So we can see them. So that sister chromatids will stay together.
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So that they will not be damaged when they are moved around the cell.
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Which of the following statements about the mitotic spindle is TRUE? Astral microtubules extend toward the opposite centrosome and overlap with polar microtubules to properly position the spindle. Microtubules in the mitotic spindle attach directly to the DNA in the centromere. Centrioles are necessary for the proper separation of sister chromatids. Kinetochore proteins make up kinetochore microtubules, which connect to the centromeres of the condensed chromosomes. Kinetochore microtubules in the mitotic spindle attempt to connect to kinetochore proteins in the centromeres of the condensed chromosomes.
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Kinetochore microtubules in the mitotic spindle attempt to connect to kinetochore proteins in the centromeres of the condensed chromosomes.
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The proteins ________ work together to free the transcription factor that is bound by the retinoblastoma protein. cyclin and cyclin dependent kinase p53 and cyclin cyclin dependent kinase and p53 cyclin and E2F p53 and p21
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cyclin and cyclin dependent kinase
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Mutated forms of the Rb protein do not bind to E2F thereby promoting uncontrolled cell division. bind to E2F thereby promoting uncontrolled cell division. bind to E2F thereby inhibiting cell division. bind to E2F but have no effect on cell division. do not bind to E2F thereby inhibiting cell division.
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do not bind to E2F thereby promoting uncontrolled cell division.
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The protein ________ checks for damaged DNA, thereby acting as a "quality control" for the cell. cyclin dependent kinase E2F cyclin p53 p21
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p53
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What mutation would allow the cell to divide when it should not and could possibly lead to cancer? A mutation causing p21 to remain active, even in the absence of a signal from p53. A mutation preventing cycling from interacting with CDK. None of these will lead to cell proliferation. A mutation causing p53 to activate p21, even when it is not necessary. A mutation preventing p21 from dissociating from cyclin.
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None of these will lead to cell proliferation.
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Which mutation would allow the cell to pass the G1 checkpoint when it should not? A mutation in Rb, preventing it from dissociating with E2F. A mutation in cyclin, preventing it from associating with CDK. A mutation in Rb, preventing it from becoming phosphorylated. A mutation in Rb, preventing it from associating with E2F. A mutation in CDK, preventing in from phosphorylating Rb.
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A mutation in Rb, preventing it from associating with E2F.
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Which of the following events occur during prophase I? Condensation of chromosomes. Breakdown of nuclear envelope and condensation of chromosomes. Breakdown of nuclear envelope. Movement of centrosomes. Breakdown of nuclear envelope, condensation of chromosomes, and movement of centrosomes.
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Breakdown of nuclear envelope, condensation of chromosomes, and movement of centrosomes.
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How many bivalents are formed in a cell with 20 chromosomes at the beginning of meiosis I? 10 40 5 20 1
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10
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Which of the following events occur during anaphase I? lengthening of kinetochore microtubules. separation of homologous chromosomes and formation of synaptonemal complex. formation of synaptonemal complex. separation of homologous chromosomes, formation of synaptonemal complex, and lengthening of kinetochore microtubules. separation of homologous chromosomes.
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separation of homologous chromosomes.
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How can you compare the complement of DNA in an interphase (G1) diploid cell and a cell that has just completed meiosis I? The meiotic cell has twice as much DNA and twice as many chromosomes. The meiotic cell has half as much DNA and half as many chromosomes. They have the same number of chromosomes, but the meiotic cell has half as much DNA. They have the same amount of DNA, but the meiotic cell has half as many chromosomes. They have the same amount of DNA, but the meiotic cell has twice as many chromosomes.
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They have the same amount of DNA, but the meiotic cell has half as many chromosomes.
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What event in meiosis I leads to the cell becoming haploid rather than the separation of sister chromatids? Crossing over may occur during prophase once bivatents have formed. Formation of bivalents lead to spindle fibers from opposite poles attaching to homologous chromosomes. All of these are important in the formation of haploid cells. During anaphase, spindle fiber shorten, pulling chromosomes to opposite sites of the cell. During early prophase, centrosomes migrate to opposite ends of the cell and begin to form the spindle apparatus. ebook & resources
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Formation of bivalents lead to spindle fibers from opposite poles attaching to homologous chromosomes.
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Nondisjunction is the failure of homologous chromosomes to separate during meiosis I, or the failure of sister chromatids to separate during meiosis II or mitosis. As a result, both homologous chromosomes or both sister chromatids migrate to the same pole of the cell. This produces daughter cells with an imbalance of chromosomes. If 22 pairs of homologous chromosomes segregate normally during meiosis I in humans (n=23) but we have nondisjunction of 1 pair, then at the end of meiosis II we will have 3 cells with 24 chromosomes and 1 cell with 22 2 cells with 24 chromosomes and 2 cells with 22 2 cells with 23 chromosomes, 1 cell with 22, and 1 cell with 24 3 cells with 22 chromosomes and 1 cell with 24
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2 cells with 24 chromosomes and 2 cells with 22
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n a human somatic cell (normal body cell) that is in G2, what would be true about chromosome number and structure? Check all that apply. These cells would be considered haploid (n). These cells would be considered diploid (2n). These cells would be considered tetraploid (4n). These cells would contain homologous chromosomes. These cells would contain sister chromatids. correct The chromosomes will be aligned in the middle of the cell.
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These cells would be considered diploid (2n). These cells would contain homologous chromosomes. These cells would contain sister chromatids. correct
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Cells that have two sets of chromosomes are
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diploid
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Cells that have one set of chromosomes are
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haploid
