Genetics Chapter 2

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 Genetics Chapter 2
Genetics Chapter 2

  
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  • 1. 
    A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of telomeres in a rat cell in G2?  
    • A. 

      21

    • B. 

      42

    • C. 

      84

    • D. 

      126

    • E. 

      168


  • 2. 
    A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of chromosomes present in the cell during metaphase I of meiosis?  
    • A. 

      21

    • B. 

      42

    • C. 

      84

    • D. 

      126

    • E. 

      168


  • 3. 
    A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of chromosomes present in the cell during metaphase I of meiosis?  
    • A. 

      21

    • B. 

      40

    • C. 

      41

    • D. 

      42

    • E. 

      84


  • 4. 
    A dividing eukaryotic cell is treated with a drug that inhibits the molecular motors associated with kinetochores. At which cell cycle stage would it stop?  
    • A. 

      G1

    • B. 

      S

    • C. 

      G2

    • D. 

      M (anaphase)

    • E. 

      M (telophase)


  • 5. 
    A eukaryotic cell in G1 has a mutation that prevents cyclin B from being made. At which cell cycle stage would this cell stop?  
    • A. 

      G1

    • B. 

      S

    • C. 

      G2

    • D. 

      M (anaphase)

    • E. 

      M (telophase)


  • 6. 

    The figure shows a chromosomal separation taking place. The letters stand for genes; capital and lowercase stand for different alleles. The diploid chromosome number in this organism is four. What process is shown?  
    • A. 

      Anaphase of mitosis

    • B. 

      Telophase of meiosis I

    • C. 

      Anaphase of meiosis I

    • D. 

      Telophase of mitosis

    • E. 

      Anaphase of meiosis II


  • 7. 
    Errors in chromosome separation are rarely a problem for an organism.  
    • A. 

      True

    • B. 

      False


  • 8. 
    The prokaryotes include both the eubacteria and the archaea.  
    • A. 

      True

    • B. 

      False


  • 9. 
    Archaea are more closely related to eukaryotes than they are to eubacteria.  
    • A. 

      True

    • B. 

      False


  • 10. 
    Generally, chromosomes of eukaryotes are circular.  
    • A. 

      True

    • B. 

      False


  • 11. 
    Cells with a single set of chromosomes are called diploid.  
    • A. 

      True

    • B. 

      False


  • 12. 
    In a flowering plant, the male part of the flower (the stamen) produces haploid microsporocyte cells that divide by _____(a)_______ to produce sperm. A pollen grain that lands on a stigma grows a pollen tube to deliver _____(b)_______  (how many?) sperm to the ovary. Fusion of a sperm with an egg produces a _____(c)_______  n cell called a _____(d)_______ . To provide food for the developing embryo, a tissue called endosperm is produced through double fertilization. Endosperm has a ploidy of _____(e)_______  n. answers: (a, b, c, d, e)  

  • 13. 
    In prokaryotes, replication usually begins at a specific place on the chromosome called ____________  

  • 14. 
    The ____________ is the highly organized internal scaffolding of the nucleus.  

  • 15. 
    The attachment point on the chromosome for spindle microtubules is the _____________.  

  • 16. 
    ____________ refers to the splitting of the cytoplasm, separating one cell into two.  

  • 17. 
    Prokaryotic chromosomes do not have telomeres because:  
    • A. 

      They do not go through mitosis.

    • B. 

      They do not go through DNA replication.

    • C. 

      They are in the cytoplasm.

    • D. 

      They are circular.

    • E. 

      They have no centromeres.


  • 18. 
    In eukaryotes, chromosomes do not contain:  
    • A. 

      Proteases

    • B. 

      Chromatin

    • C. 

      Proteins

    • D. 

      Histones

    • E. 

      DNA


  • 19. 
    In order to be functional, a chromosome requires all of the following except:  
    • A. 

      Centromeres

    • B. 

      Origins of replication

    • C. 

      Nucleomeres

    • D. 

      Telomeres


  • 20. 
    What process is unique to plants?  
    • A. 

      Meiosis

    • B. 

      Double fertilization

    • C. 

      Crossing over

    • D. 

      Haploid gametes

    • E. 

      Spermatogenesis


  • 21. 
    Chromosomes are in unseparated, sister-chromatid form, at the end of the phase(s)  
    • A. 

      Meiosis I prophase

    • B. 

      Meiosis I anaphase

    • C. 

      Meiosis II prophase

    • D. 

      Meiosis II anaphase

    • E. 

      Mitosis prophase

    • F. 

      Mitosis anaphase


  • 22. 
    The first stage after which a dividing cell that started as a diploid would be haploid  
    • A. 

      Meiosis I prophase

    • B. 

      Meiosis I anaphase

    • C. 

      Meiosis II prophase

    • D. 

      Meiosis II anaphase

    • E. 

      Mitosis prophase

    • F. 

      Mitosis anaphase


  • 23. 
    Sister chromatids separate during  
    • A. 

      Meiosis I prophase

    • B. 

      Meiosis I anaphase

    • C. 

      Meiosis II prophase

    • D. 

      Meiosis II anaphase

    • E. 

      Mitosis prophase

    • F. 

      Mitosis anaphase


  • 24. 
    Chromosomes are randomly partitioned during_____, contributing to genetic diversity.  
    • A. 

      Meiosis I prophase

    • B. 

      Meiosis I anaphase

    • C. 

      Meiosis II prophase

    • D. 

      Meiosis II anaphase

    • E. 

      Mitosis prophase

    • F. 

      Mitosis anaphase


  • 25. 
    Crossing over (genetic recombination) occurs in_________.  
    • A. 

      Meiosis I prophase

    • B. 

      Meiosis I anaphase

    • C. 

      Meiosis II prophase

    • D. 

      Meiosis II anaphase

    • E. 

      Mitosis prophase

    • F. 

      Mitosis anaphase


  • 26. 
    Pea plants have seven different types of chromosomes.  True or False? A diploid pea cell in G1 has 14 centrioles.  
    • A. 

      True

    • B. 

      False


  • 27. 
    Pea plants have seven different types of chromosomes. The nucleus of a megaspore in a pea ovary would contain how many chromosomes?  

  • 28. 
    Pea plants have seven different types of chromosomes. A nucleus in the pea endosperm contains how many chromosomes?  

  • 29. 
    A chromosome with a centromere at the very end is called  
    • A. 

      Submetacentric

    • B. 

      Metacentric

    • C. 

      Acrocentric

    • D. 

      Acentric

    • E. 

      Telocentric


  • 30. 
    During prophase I of meiosis, crossing over is indicated by what microscopically visible structure?  
    • A. 

      Telomere

    • B. 

      Mitotic cell

    • C. 

      Chiasmata (chiasma)

    • D. 

      The synaptonemal complex

    • E. 

      None of the above


  • 31. 
    List differences between mitosis and meiosis.  
    • A. 

      Mitosis occurs in somatic (nonsex) cells; meiosis occurs in sex cells to produce gametes.

    • B. 

      Meiosis involves chromosome pairing (of homologous chromosomes); mitosis does not.

    • C. 

      Mitosis produces nonsex cells; meiosis produces gametes.

    • D. 

      Mitosis has two consecutive divisions; Meiosis has one.

    • E. 

      Mitosis produces cells of the same ploidy; meiosis produces haploid cells from diploid cells.

    • F. 

      Meiosis has two consecutive divisions; mitosis has one.

    • G. 

      Mitosis involves chromosome pairing (of homologous chromosomes); meiosis does not.

    • H. 

      Mitosis produces identical daughter cells; meiosis produces four different daughter cells.


  • 32. 
    List similarities between mitosis and meiosis  
    • A. 

      Both involve the separation of replicated chromosomes during cell division.

    • B. 

      Cytokinesis usually occurs at the beginning of each.

    • C. 

      Both are processes to ensure that daughter cells in cell division receive a complete set of chromosomes.

    • D. 

      DNA replication occurs after Cytokinesis

    • E. 

      DNA replication must occur first.

    • F. 

      Cytokinesis usually occurs at the end of each.


  • 33. 
    The complete genetic makeup of any organism is its genome. A gene is a unit of that genome. A gene is a section of a chromosome that encodes an RNA molecule or a single polypeptide (protein).  
    • A. 

      True

    • B. 

      False


  • 34. 
    A centromere is the physical location on a chromosome where the kinetochore and spindle microtubules attach. The kinetochore is composed of proteins that assemble on the centromere to provide a site for the spindle microtubules to attach.  
    • A. 

      True

    • B. 

      False


  • 35. 
    G1 occurs before S phase and G2 occurs after S phase. During G1, cells grow in size, chromosomes are composed of a single chromatid, and cyclin B levels are low. During G1, cells pass a critical checkpoint (the G1/S checkpoint) after which they are committed to undergoing cell division. During G2, the chromosomes are composed of two chromatids and cyclin B levels rise. There is another checkpoint during G2 that ensures cells are prepared for mitosis. Cells typically spend more time in G1 than in G2.  
    • A. 

      True

    • B. 

      False


  • 36. 
    Homologous chromosomes have different alleles. Sister chromatids are duplicates and (except for errors in replication) are identical in sequence.  
    • A. 

      True

    • B. 

      False


  • 37. 
    Homologs pair and segregate in meiosis I. Sister chromatids are paired and segregate in meiosis II. Crossing over occurs in meiosis I, but not in meiosis II.  
    • A. 

      True

    • B. 

      False


  • 38. 
    The sporophyte is the diploid phase of a plant life cycle. The gametophyte is the haploid stage.  
    • A. 

      True

    • B. 

      False


  • 39. 
    Viruses can reproduce only within host cells. Thus, they must have evolved after cells.  
    • A. 

      True

    • B. 

      False


  • 40. 
    What feature of meiosis produces genetic variability in gametes?  
    • A. 

      Independent Assortment

    • B. 

      Crossing Over

    • C. 

      Chromosomes

    • D. 

      A and B are correct


  • 41. 
    In meiosis I—metaphase and anaphase—nonhomologous chromosomes distribute randomly. Alignment and separation of one pair of homologous chromosomes is independent of how a different pair separates. Different gametes have different combinations of the paternally derived and maternally derived chromosomes. These chromosomes have different alleles for the same genes, so the gametes have different combinations of alleles.  
    • A. 

      True

    • B. 

      False


  • 42. 
    Crossing over.  In meiosis I—prophase—portions of homologous chromosomes exchange, changing combinations of alleles of genes on a single chromosome, so not even sister chromatids are identical after crossing over. Each gamete has only one copy of each homolog, and each homolog now has a unique combination of alleles.  
    • A. 

      True

    • B. 

      False


  • 43. 

     
    • A. 

      A pair of telocentric homologous chromosomes as they would appear in G2. Indicate centromeres with a small circle, and place the alleles A and a on each of the chromatids.

    • B. 

      A pair of telocentric heterozygous chromosomes as they would appear in G2. Indicate centromeres with a small circle, and place the alleles A and a on each of the chromatids.

    • C. 

      Both A and B

    • D. 

      Neither A or B


  • 44. 

     
    • A. 

      A pair of telocentric homologous chromosomes as they would appear in G1. Place the alleles A and a on each of the chromatids.

    • B. 

      A pair of telocentric homologous chromosomes as they would appear in G2. Place the alleles A and a on each of the chromatids.

    • C. 

      Both A and B

    • D. 

      Neither A nor B


  • 45. 
    Why is mitosis important within the cell cycle?  
    • A. 

      A single cell and all its genetic information is duplicated.

    • B. 

      Each cell contains a full complement of chromosomes.

    • C. 

      Both A and B

    • D. 

      Neither A or B


  • 46. 
    Explain why mitosis does not produce genetic variation and how meiosis leads to the production of tremendous genetic variation.  
    • A. 

      Mitosis produces cells that are genetically identical to the parent cell.

    • B. 

      Viruses replicate using binary fission

    • C. 

      Meiosis includes two distinct processes that contribute to the generation of genetic variation: crossing over shuffles alleles on the same chromosome into new combinations, whereas the random distribution of maternal and paternal chromosomes shuffles alleles on different chromosomes into new combinations.


  • 47. 
    Microscopy to look at a cell's chromosomes is often done when the cell is in mitotic metaphase. For example, karyotypes that extract chromosomes from a single cell and photograph them to look for abnormalities are done on metaphase, rather than interphase, cells. Why?  
    • A. 

      In metaphase, chromosomes are condensed and are more easily visualized.

    • B. 

      In metaphase, chromosomes are expanded and are more easily visualized.

    • C. 

      Both A and B

    • D. 

      Neither A or B


  • 48. 

    Find and describe at least four errors in the drawing below of mitotic anaphase.  
    • A. 

      Spindles are replicating

    • B. 

      Chromosomes that are separating are still duplicated.

    • C. 

      Not enough information

    • D. 

      Spindles are not coming from a common spindle-pole body.

    • E. 

      Sister chromatids do not have identical alleles for the B gene.

    • F. 

      Two alleles of the D gene are on one chromosome.

    • G. 

      No alleles of the A gene are on the homologous chromosome.

    • H. 

      Homologous chromosomes appear to have paired and to be segregating.


  • 49. 
    The mitochondria within eukaryotic cells have their own genomes. Imagine that a mutation arises on the mitochondrial genome and, at the time of cytokinesis of the host cell, 10% of the mitochondria in that cell have that mutation. In the two daughter cells, what percentage of the mitochondria will possess that mutation?  
    • A. 

      Although the cytoplasm containing the mitochondria will be equally divided between the two cells, there is no precise mechanism for ensuring that the organelles are equally divided.

    • B. 

      One cannot accurately predict what the percentages will be in each cell.

    • C. 

      50% each

    • D. 

      A and B only

    • E. 

      None of the above


  • 50. 
    What events during sexual reproduction are significant in contributing to genetic diversity?  
    • A. 

      Crossing over changes allele combinations on chromosomes, so, after meiosis I, even sister chromatids are not genetically identical.

    • B. 

      Independent assortment of non-homologous chromosomes ensures each gamete has a different combination of alleles for genes on nonhomologs.

    • C. 

      Sister chromatids are always genetically identical.

    • D. 

      Two genetically unique gametes from each parent combine during fertilization to form a novel, genetically unique individual.


  • 51. 
    In tissue from the intestinal epithelium of a frog, the following proportions of cells were found at each stage of the cell cycle: Stage Proportion of Cells Interphase 0.90 Prophase 0.04 Prometaphase 0.02 Metaphase 0.01 Anaphase 0.02 Telophase 0.01 If the entire cell cycle in frog epithelium cells requires 20 hours for completion, what is the average duration of each stage?  
    • A. 

      0.9 × 10 = 9 hours, 0.04 × 10 = 0.4 hours, .02 × 10 = .2 hours, etc.

    • B. 

      0.9 × 20 = 18 hours, 0.04 × 20 = 0.8 hours, .02 × 20 = .4 hours, etc.

    • C. 

      Not enough information to predict

    • D. 

      None of the above


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