Genetics Trivia Quiz: Chromosomes And Cellular Reproduction

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Genetics Trivia Quiz: Chromosomes And Cellular Reproduction - Quiz

All living things have chromosomes within them, which are useful when it comes to cellular reproduction. Cells usually break apart to form new ones and in so doing the chromosomes duplicate themselves. Just how much do you know about the different chromosomes within our bodies and the process of cell reproduction? Take up this test and get to find out!


Questions and Answers
  • 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

    Correct Answer
    E. 168
    Explanation
    In G2 phase, the cell has already replicated its DNA, resulting in two identical sister chromatids held together at the centromere. Each chromatid has one telomere at the end, so there are 2 telomeres per chromatid. Since there are 42 chromosomes in the rat cell, and each chromosome has 2 chromatids, there are a total of 84 chromatids. Therefore, there are 2 telomeres per chromatid, resulting in a total of 168 telomeres in the rat cell in G2.

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  • 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

    Correct Answer
    B. 42
    Explanation
    During metaphase I of meiosis, the cell undergoes homologous chromosome pairing and aligns them at the equator of the cell. Each homologous pair consists of two sister chromatids, so the total number of chromosomes present in the cell remains the same. Since the diploid somatic cell from a rat has a total of 42 chromosomes, the total number of chromosomes present in the cell during metaphase I of meiosis is also 42.

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  • 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

    Correct Answer
    A. 21
    Explanation
    During metaphase I of meiosis, the cell undergoes a process called homologous chromosome pairing, where homologous chromosomes line up at the center of the cell. Since a diploid somatic cell from a rat has a total of 42 chromosomes, during metaphase I of meiosis, there will be half of that number, which is 21 chromosomes. This is because during meiosis I, the cell undergoes reduction division, where the chromosome number is reduced by half. Therefore, the correct answer is 21.

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  • 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)

    Correct Answer
    D. M (anaphase)
    Explanation
    When a dividing eukaryotic cell is treated with a drug that inhibits the molecular motors associated with kinetochores, it would stop at the stage of M (anaphase). This is because during anaphase, the kinetochores are responsible for pulling the sister chromatids apart, ensuring that each daughter cell receives the correct number of chromosomes. By inhibiting the molecular motors associated with kinetochores, the drug prevents this separation, causing the cell to stop at this stage.

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  • 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)

    Correct Answer
    A. G1
    Explanation
    If a eukaryotic cell in G1 has a mutation that prevents cyclin B from being made, this cell would stop at the G1 stage. Cyclin B is necessary for the progression of the cell cycle from G1 to S phase. Without cyclin B, the cell cannot proceed to the next stage and would remain in G1.

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  • 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

    Correct Answer
    E. Anaphase of meiosis II
    Explanation
    The correct answer is anaphase of meiosis II. This is because in anaphase of meiosis II, the sister chromatids of each chromosome separate and move towards opposite poles of the cell. This results in the formation of haploid cells with half the number of chromosomes as the original cell. Since the question states that the diploid chromosome number in this organism is four, the process shown must be anaphase of meiosis II.

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  • 7. 

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

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Chromosome separation errors, also known as chromosomal abnormalities, can have significant negative effects on an organism. These errors can lead to genetic disorders or developmental issues that can impact the organism's health and survival. Therefore, it is incorrect to say that errors in chromosome separation are rarely a problem for an organism.

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  • 8. 

    The prokaryotes include both the eubacteria and the archaea.  

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The statement is true because prokaryotes are a group of organisms that lack a nucleus and membrane-bound organelles. This group includes both the eubacteria, which are commonly referred to as bacteria, and the archaea. Both eubacteria and archaea are single-celled organisms that have a simple cell structure and lack a nucleus. Therefore, the statement that prokaryotes include both the eubacteria and archaea is correct.

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  • 9. 

    Archaea are more closely related to eukaryotes than they are to eubacteria.  

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Archaea are more closely related to eukaryotes than they are to eubacteria because they share several genetic and biochemical characteristics with eukaryotes. These include similarities in the structure of their DNA, RNA, and ribosomes, as well as the presence of introns in their genes. Additionally, archaea and eukaryotes both have similar membrane lipids, while eubacteria have different types of lipids. These similarities suggest a closer evolutionary relationship between archaea and eukaryotes.

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  • 10. 

    Generally, chromosomes of eukaryotes are circular.  

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    The statement is false because chromosomes in eukaryotes are not generally circular. In eukaryotes, chromosomes are linear structures that contain DNA and proteins. They are organized into multiple linear strands and are located in the nucleus of the cell. The circular shape is more commonly found in prokaryotes, such as bacteria.

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  • 11. 

    Cells with a single set of chromosomes are called diploid.  

    • A.

      True

    • B.

      False

    Correct Answer
    B. False
    Explanation
    Cells with a single set of chromosomes are actually called haploid, not diploid. Diploid cells have two sets of chromosomes.

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  • 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)  

    Correct Answer
    mitosis, 2, 2, zygote, 3
    Explanation
    The correct answers are as follows:
    (a) The microsporocyte cells divide by mitosis to produce sperm.
    (b) A pollen grain delivers 2 sperm to the ovary through the pollen tube.
    (c) Fusion of a sperm with an egg produces a 2n cell called a zygote.
    (d) To provide food for the developing embryo, endosperm is produced through double fertilization.
    (e) Endosperm has a ploidy of 3n.

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  • 13. 

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

    Correct Answer
    the origin of replication
    origin of replication
    Explanation
    The correct answer is "the origin of replication". In prokaryotes, replication begins at a specific place on the chromosome called the origin of replication. This is the site where the replication machinery attaches and initiates the process of DNA replication. The origin of replication is a crucial element in ensuring that the entire chromosome is duplicated accurately during cell division.

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  • 14. 

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

    Correct Answer
    nuclear matrix
    Explanation
    The nuclear matrix refers to the highly organized internal scaffolding of the nucleus. It provides structural support and organization to the nucleus, helping to maintain its shape and integrity. The nuclear matrix also plays a role in various nuclear processes such as DNA replication, transcription, and RNA processing. It acts as a framework for the attachment of chromatin and other nuclear components, facilitating their interactions and functions within the nucleus.

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  • 15. 

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

    Correct Answer
    centromere
    Explanation
    The centromere is the attachment point on the chromosome for spindle microtubules. It is a region of DNA that holds the sister chromatids together during cell division and plays a crucial role in ensuring the proper separation of chromosomes. The spindle microtubules attach to the centromere and exert forces that pull the sister chromatids apart, allowing them to be distributed equally into the daughter cells.

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  • 16. 

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

    Correct Answer
    Cytokinesis
    Explanation
    Cytokinesis refers to the process of dividing the cytoplasm of a cell, resulting in the formation of two separate daughter cells. This occurs after the nuclear division (mitosis or meiosis) and is essential for the completion of cell division. During cytokinesis, a contractile ring composed of actin and myosin filaments forms around the equator of the cell, constricting and eventually pinching the cell into two daughter cells. This process ensures that each daughter cell receives a complete set of genetic material and organelles, allowing for growth and development.

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  • 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.

    Correct Answer
    D. They are circular.
    Explanation
    Prokaryotic chromosomes do not have telomeres because they are circular. Unlike eukaryotic chromosomes that are linear, prokaryotic chromosomes are circular in shape. Telomeres are specialized structures found at the ends of linear chromosomes in eukaryotes, which help protect the DNA from degradation and prevent the loss of genetic material during DNA replication. Since prokaryotic chromosomes are circular and do not have distinct ends, they do not require telomeres for the same purpose.

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  • 18. 

    In eukaryotes, chromosomes do not contain:  

    • A.

      Proteases

    • B.

      Chromatin

    • C.

      Proteins

    • D.

      Histones

    • E.

      DNA

    Correct Answer
    A. Proteases
    Explanation
    Chromosomes in eukaryotes do not contain proteases. Proteases are enzymes responsible for breaking down proteins. Chromosomes, on the other hand, are structures in the nucleus that contain DNA, histones, and other proteins. Chromatin refers to the complex of DNA and proteins that make up chromosomes. Therefore, the correct answer is proteases, as they are not a component of chromosomes in eukaryotes.

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  • 19. 

    In order to be functional, a chromosome requires all of the following except:  

    • A.

      Centromeres

    • B.

      Origins of replication

    • C.

      Nucleomeres

    • D.

      Telomeres

    Correct Answer
    C. Nucleomeres
    Explanation
    Chromosomes are structures found in the nucleus of cells that contain genetic material. They are made up of DNA and proteins, and are responsible for carrying and transmitting genetic information. Centromeres are essential for the proper segregation of chromosomes during cell division. Origins of replication are necessary for DNA replication to occur. Telomeres are protective caps at the ends of chromosomes that prevent degradation and fusion. Nucleomeres, on the other hand, are not a known component of chromosomes. Therefore, nucleomeres are not required for a chromosome to be functional.

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  • 20. 

    What process is unique to plants?  

    • A.

      Meiosis

    • B.

      Double fertilization

    • C.

      Crossing over

    • D.

      Haploid gametes

    • E.

      Spermatogenesis

    Correct Answer
    B. Double fertilization
    Explanation
    Double fertilization is a process that is unique to plants. It involves the fusion of two sperm cells with two different female gametes, resulting in the formation of both a zygote and endosperm. This process is essential for the development of seeds in flowering plants and is not found in any other organisms.

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  • 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

    Correct Answer(s)
    A. Meiosis I prophase
    B. Meiosis I anaphase
    C. Meiosis II prophase
    E. Mitosis prophase
    Explanation
    During the prophase of Meiosis I, the chromosomes condense and pair up with their homologous partner, forming a structure called a bivalent. Sister chromatids remain attached at their centromeres. During the anaphase of Meiosis I, the homologous chromosomes separate and move to opposite poles of the cell. In Meiosis II prophase, the chromosomes recondense after a brief interphase. In Mitosis prophase, the chromosomes condense and become visible. Therefore, the correct answer includes Meiosis I prophase, Meiosis I anaphase, Meiosis II prophase, and Mitosis prophase as the chromosomes are in unseparated, sister-chromatid form during these phases.

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  • 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

    Correct Answer
    B. Meiosis I anaphase
    Explanation
    During Meiosis I anaphase, the homologous chromosomes separate and move towards opposite poles of the cell. This results in the formation of two daughter cells, each containing one set of chromosomes. Therefore, at this stage, the dividing cell that started as a diploid becomes haploid, meaning it now contains half the number of chromosomes as the original cell.

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  • 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

    Correct Answer(s)
    D. Meiosis II anaphase
    F. Mitosis anaphase
    Explanation
    During anaphase of both Meiosis II and Mitosis, the sister chromatids separate. In Meiosis II, the sister chromatids separate and move towards opposite poles of the cell, resulting in the formation of haploid daughter cells. In Mitosis, the sister chromatids separate and move towards opposite poles of the cell, resulting in the formation of two identical daughter cells with the same number of chromosomes as the parent cell. Therefore, both Meiosis II anaphase and Mitosis anaphase involve the separation of sister chromatids.

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  • 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

    Correct Answer
    B. Meiosis I anaphase
    Explanation
    During Meiosis I anaphase, the homologous chromosomes separate and move to opposite poles of the cell. This random partitioning of chromosomes contributes to genetic diversity because it results in the formation of different combinations of alleles in the daughter cells. This process is known as independent assortment, and it allows for the shuffling of genetic material and the creation of new combinations of genes.

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  • 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

    Correct Answer
    A. Meiosis I prophase
    Explanation
    During meiosis I prophase, crossing over (genetic recombination) occurs. This is the stage where homologous chromosomes pair up and exchange genetic material, resulting in the mixing of genetic information between the chromosomes. This process increases genetic diversity and plays a crucial role in the formation of gametes.

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  • 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

    Correct Answer
    B. False
    Explanation
    A diploid pea cell in G1 does not have 14 centrioles. Centrioles are structures that are involved in cell division and are usually found in pairs. In G1 phase, the cell is preparing for DNA replication and centrioles are not actively involved in this process. Therefore, a diploid pea cell in G1 would typically have two centrioles, not 14.

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  • 27. 

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

    Correct Answer
    7
    Explanation
    The correct answer is 7 because the question states that pea plants have seven different types of chromosomes. Therefore, the nucleus of a megaspore in a pea ovary would contain the same number of chromosomes, which is 7.

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  • 28. 

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

    Correct Answer
    21
  • 29. 

    A chromosome with a centromere at the very end is called  

    • A.

      Submetacentric

    • B.

      Metacentric

    • C.

      Acrocentric

    • D.

      Acentric

    • E.

      Telocentric

    Correct Answer
    E. Telocentric
    Explanation
    A chromosome with a centromere at the very end is called telocentric. In telocentric chromosomes, the centromere is located at one of the ends, resulting in a long arm and a very short or absent short arm. This configuration gives the chromosome a "T" shape when viewed under a microscope. Telocentric chromosomes are found in some species, including plants and insects, but are rare in mammals.

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  • 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

    Correct Answer(s)
    C. Chiasmata (chiasma)
    D. The synaptonemal complex
    Explanation
    During prophase I of meiosis, crossing over is indicated by the presence of chiasmata (also known as chiasma). Chiasmata are visible under a microscope and represent the physical exchange of genetic material between homologous chromosomes. This exchange occurs during the process of crossing over, where sections of DNA are swapped between chromatids. The synaptonemal complex, on the other hand, is a protein structure that holds homologous chromosomes together during prophase I but is not directly involved in indicating crossing over. Therefore, the correct answer is chiasmata (chiasma).

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  • 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.

    Correct Answer(s)
    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.
    E. Mitosis produces cells of the same ploidy; meiosis produces haploid cells from diploid cells.
    F. Meiosis has two consecutive divisions; mitosis has one.
    H. Mitosis produces identical daughter cells; meiosis produces four different daughter cells.
    Explanation
    Mitosis and meiosis are both processes of cell division, but they have several differences. Mitosis occurs in somatic (nonsex) cells, while meiosis occurs in sex cells to produce gametes. Meiosis involves chromosome pairing of homologous chromosomes, while mitosis does not. Mitosis produces nonsex cells, while meiosis produces gametes. Mitosis has two consecutive divisions, while meiosis has one. Mitosis produces cells of the same ploidy, while meiosis produces haploid cells from diploid cells. Finally, mitosis produces identical daughter cells, while meiosis produces four different daughter cells.

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  • 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.

    Correct Answer(s)
    A. Both involve the separation of replicated chromosomes during cell division.
    C. Both are processes to ensure that daughter cells in cell division receive a complete set of chromosomes.
    E. DNA replication must occur first.
    F. Cytokinesis usually occurs at the end of each.
    Explanation
    Mitosis and meiosis both involve the separation of replicated chromosomes during cell division. They are both processes that ensure that daughter cells receive a complete set of chromosomes. DNA replication must occur before both processes. Additionally, cytokinesis usually occurs at the end of both mitosis and meiosis.

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  • 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

    Correct Answer
    A. True
    Explanation
    The statement is true because a gene is indeed a unit of an organism's genome. It is a specific section of a chromosome that contains the instructions for producing an RNA molecule or a protein. Genes are responsible for determining various traits and characteristics of an organism.

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  • 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

    Correct Answer
    A. True
    Explanation
    The explanation for the given correct answer is that a centromere is indeed the physical location on a chromosome where the kinetochore and spindle microtubules attach. The kinetochore is a structure composed of proteins that assemble on the centromere, providing a site for the attachment of spindle microtubules. Therefore, the statement is true.

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  • 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

    Correct Answer
    A. True
    Explanation
    During G1 phase, cells grow in size, chromosomes have a single chromatid, and cyclin B levels are low. This phase is followed by the G1/S checkpoint, where cells make the decision to undergo cell division. G2 phase occurs after S phase, where chromosomes have two chromatids and cyclin B levels increase. There is another checkpoint during G2 to ensure cells are ready for mitosis. It is true that cells typically spend more time in G1 phase than in G2 phase.

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  • 36. 

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

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Homologous chromosomes are pairs of chromosomes that contain the same genes, but may have different alleles (variations of a gene). Sister chromatids, on the other hand, are identical copies of each other formed during DNA replication. Therefore, it is true that homologous chromosomes have different alleles, while sister chromatids are duplicates and identical in sequence.

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  • 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

    Correct Answer
    A. True
    Explanation
    In meiosis I, homologous chromosomes pair up and segregate, while in meiosis II, sister chromatids separate. This is because meiosis I is the stage where crossing over occurs, which is the exchange of genetic material between homologous chromosomes. Meiosis II, on the other hand, is similar to mitosis, where sister chromatids separate to form haploid cells. Therefore, the statement that homologs pair and segregate in meiosis I, while sister chromatids pair and segregate in meiosis II, is true.

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  • 38. 

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

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    The explanation for the correct answer is that in the plant life cycle, the sporophyte stage is the diploid phase, meaning it has two sets of chromosomes. This stage is responsible for producing spores through meiosis. On the other hand, the gametophyte stage is the haploid stage, meaning it has only one set of chromosomes. This stage produces gametes through mitosis. Therefore, it is true that the sporophyte is the diploid phase and the gametophyte is the haploid stage in the plant life cycle.

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  • 39. 

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

    • A.

      True

    • B.

      False

    Correct Answer
    A. True
    Explanation
    Viruses can only reproduce within host cells because they lack the necessary cellular machinery to carry out their own replication. This dependence on host cells suggests that viruses evolved after cells, as they rely on pre-existing cellular structures and processes for their replication and survival. Therefore, the statement is true.

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  • 40. 

    What feature of meiosis produces genetic variability in gametes?  

    • A.

      Independent Assortment

    • B.

      Crossing Over

    • C.

      Chromosomes

    • D.

      A and B are correct

    Correct Answer
    D. A and B are correct
    Explanation
    Independent assortment and crossing over both contribute to genetic variability in gametes during meiosis. Independent assortment occurs during the separation of homologous chromosomes in meiosis I, where the orientation of the chromosomes on the metaphase plate is random. This random arrangement leads to different combinations of alleles in the gametes. Crossing over, on the other hand, occurs during prophase I of meiosis, where homologous chromosomes exchange genetic material. This exchange results in the recombination of alleles, further increasing genetic diversity in the gametes. Therefore, both independent assortment and crossing over are responsible for producing genetic variability in gametes.

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  • 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

    Correct Answer
    A. True
    Explanation
    In meiosis I, nonhomologous chromosomes distribute randomly during metaphase and anaphase. This means that the alignment and separation of one pair of homologous chromosomes is independent of how a different pair separates. As a result, different gametes will have different combinations of the paternally derived and maternally derived chromosomes. Since these chromosomes have different alleles for the same genes, the gametes will also have different combinations of alleles. Therefore, the statement "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" is true.

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  • 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

    Correct Answer
    A. True
    Explanation
    During meiosis I, specifically in prophase, crossing over occurs. This process involves portions of homologous chromosomes exchanging, resulting in a change in combinations of alleles of genes on a single chromosome. As a result, even sister chromatids are not identical after crossing over. Each gamete produced in meiosis has only one copy of each homolog, and due to crossing over, each homolog now possesses a unique combination of alleles. Therefore, the statement "Crossing over occurs in meiosis I, resulting in unique combinations of alleles on homologous chromosomes" is true.

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  • 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

    Correct Answer
    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.
    Explanation
    The correct answer is a pair of telocentric homologous chromosomes as they would appear in G2. This is because the question specifically asks for the chromosomes to be telocentric and homologous, and to indicate the centromeres and alleles on each chromatid.

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  • 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

    Correct Answer
    A. A pair of telocentric homologous chromosomes as they would appear in G1. Place the alleles A and a on each of the chromatids.
    Explanation
    The correct answer is a pair of telocentric homologous chromosomes as they would appear in G1. This is because in G1 phase of the cell cycle, the chromosomes are fully replicated and consist of two sister chromatids held together by a centromere. The alleles A and a are placed on each of the chromatids, indicating that they are present on both copies of the chromosome. In G2 phase, the chromosomes have undergone DNA replication but have not yet separated, so the correct answer is not G2.

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  • 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

    Correct Answer
    D. Neither A or B
    Explanation
    Mitosis is important within the cell cycle because it allows for the division of a single cell into two identical daughter cells. This process ensures that each new cell receives a full complement of chromosomes, which is crucial for the maintenance of genetic information and the proper functioning of the organism. Therefore, the correct answer is neither A nor B.

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  • 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.

    Correct Answer(s)
    A. Mitosis produces cells that are genetically identical to the parent cell.
    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.
    Explanation
    Mitosis does not produce genetic variation because it involves the replication and division of a single cell, resulting in two identical daughter cells. There is no exchange or shuffling of genetic material during mitosis. On the other hand, meiosis includes two processes that contribute to the production of genetic variation. Crossing over occurs during prophase I, where homologous chromosomes exchange genetic material, leading to new combinations of alleles on the same chromosome. Additionally, during the random distribution of maternal and paternal chromosomes in anaphase I, different combinations of alleles on different chromosomes are shuffled, further increasing genetic variation.

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  • 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

    Correct Answer
    A. In metaphase, chromosomes are condensed and are more easily visualized.
    Explanation
    In metaphase, chromosomes are condensed and tightly packed, making them easier to visualize under a microscope. This is because during metaphase, the chromosomes have already replicated and have formed sister chromatids that are held together by a structure called the centromere. The condensed and organized nature of the chromosomes in metaphase allows for better identification and analysis of their structure, number, and any abnormalities that may be present. In contrast, during interphase, chromosomes are in a less condensed and more dispersed state, which makes it more difficult to observe and analyze them accurately.

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  • 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.

    Correct Answer(s)
    B. Chromosomes that are separating are still duplicated.
    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.
    Explanation
    The drawing of mitotic anaphase contains several errors. Firstly, the chromosomes that are separating are still duplicated, which is incorrect as they should be fully separated. Secondly, the spindles are not coming from a common spindle-pole body, which is a mistake as they should originate from the poles. Thirdly, the sister chromatids do not have identical alleles for the B gene, which is inaccurate as they should have the same genetic information. Fourthly, two alleles of the D gene are on one chromosome, which is incorrect as each chromosome should only have one allele. Additionally, no alleles of the A gene are present on the homologous chromosome, which is incorrect as there should be alleles present. Lastly, the homologous chromosomes appear to have paired and be segregating, which is incorrect as they should be fully separated.

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  • 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

    Correct Answer
    D. A and B only
    Explanation
    During cytokinesis, the cytoplasm containing the mitochondria is divided equally between the two daughter cells. However, there is no precise mechanism for ensuring that the organelles are equally divided. Therefore, it is not possible to accurately predict the percentages of mitochondria with the mutation in each cell. Hence, both options A and B, which state that the percentages cannot be determined accurately, are correct.

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  • 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.

    Correct Answer(s)
    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.
    D. Two genetically unique gametes from each parent combine during fertilization to form a novel, genetically unique individual.
    Explanation
    During sexual reproduction, crossing over occurs during meiosis I, which changes the allele combinations on chromosomes. This results in even sister chromatids being genetically different. Additionally, independent assortment of non-homologous chromosomes ensures that each gamete has a different combination of alleles for genes on non-homologs. Finally, two genetically unique gametes from each parent combine during fertilization to form a novel, genetically unique individual. These events contribute to genetic diversity by introducing new combinations of alleles and creating unique individuals.

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  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
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    Quiz Created by
    Andreazza

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