Biology Exam 4 Pt. 1

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Biology Quizzes & Trivia

Questions and Answers
  • 1. 

    A bacterial cell gives rise to two genetically identical daughter cells by a process known as

    • A.

      Nondisjunction.

    • B.

      Mitosis.

    • C.

      Meiosis.

    • D.

      Fission.

    • E.

      Fertilization.

    Correct Answer
    D. Fission.
    Explanation
    Fission is the correct answer because it is the process by which a bacterial cell divides into two genetically identical daughter cells. During fission, the bacterial cell replicates its DNA and then divides into two separate cells, each containing a complete copy of the genetic material. This process is different from mitosis and meiosis, which are involved in the division of eukaryotic cells, and fertilization, which is the fusion of gametes to form a zygote. Nondisjunction refers to the failure of chromosomes to separate properly during cell division and is not relevant to bacterial cell division.

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  • 2. 

    In order for a prokaryote cell to divide, which of the following must occur?

    • A.

      A reproductive signal, replication, segregation of DNA and cytokinesis

    • B.

      DNA replication, crossing over, and segregation of DNA

    • C.

      DNA replication and segregation of DNA

    • D.

      Cell growth and cytokinesis

    • E.

      DNA replication, segregation of DNA, and cytokinesis

    Correct Answer
    A. A reproductive signal, replication, segregation of DNA and cytokinesis
  • 3. 

    Bacteria typically have ____, whereas eukaryotes have ____

    • A.

      One chromosome that is circular; many chromosomes that are linear

    • B.

      Several chromosomes that are circular; many chromosomes that are linear

    • C.

      One chromosome that is linear; many chromosomes that are circular

    • D.

      Two chromosomes that are circular; eight chromosomes that are linear

    • E.

      None of the above

    Correct Answer
    A. One chromosome that is circular; many chromosomes that are linear
    Explanation
    Bacteria typically have one chromosome that is circular, whereas eukaryotes have many chromosomes that are linear. This is because bacteria have a simpler cellular structure and their genetic material is organized in a single circular chromosome located in the nucleoid region. On the other hand, eukaryotes have a more complex cellular structure and their genetic material is organized in multiple linear chromosomes located within the nucleus. This difference in chromosome structure is one of the key distinctions between bacteria and eukaryotes.

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  • 4. 

    Which of the following statements about mitosis is true?

    • A.

      The chromosome number in the resulting cells is halved.

    • B.

      DNA replication is completed in prophase.

    • C.

      Crossing over occurs during prophase.

    • D.

      Two genetically identical daughter cells are formed.

    • E.

      It consists of two nuclear divisions.

    Correct Answer
    D. Two genetically identical daughter cells are formed.
    Explanation
    During mitosis, a single cell divides into two genetically identical daughter cells. This process ensures that each daughter cell receives an exact copy of the parent cell's genetic material. The other statements are incorrect: the chromosome number is not halved but remains the same, DNA replication occurs in the S phase of interphase and not in prophase, crossing over occurs during meiosis and not mitosis, and mitosis consists of only one nuclear division.

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  • 5. 

    DNA replication occurs

    • A.

      During both mitosis and meiosis

    • B.

      Only during mitosis

    • C.

      Only during meiosis

    • D.

      During the S phase

    • E.

      During G2

    Correct Answer
    D. During the S phase
    Explanation
    DNA replication occurs during the S phase of the cell cycle. This is the phase where the cell prepares to divide by duplicating its DNA. During mitosis, the replicated DNA is separated into two daughter cells, while during meiosis, the replicated DNA is divided into four daughter cells. Therefore, DNA replication occurs during both mitosis and meiosis, but it specifically takes place during the S phase of the cell cycle.

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  • 6. 

    The cells of the intestinal epithelium are continually dividing, replacing dead cells lost from teh surface of the intestinal lining.  If you examined a population of intestinal epithelial cells under the microscope, most of the cells would 

    • A.

      Be in meiosis.

    • B.

      Be in mitosis.

    • C.

      Be in interphase.

    • D.

      Have condensed chromatin.

    • E.

      Both b and d

    Correct Answer
    C. Be in interphase.
    Explanation
    The correct answer is "be in interphase." Interphase is the longest phase of the cell cycle and is characterized by cell growth and DNA replication. In the context of the intestinal epithelium, where cells are constantly dividing to replace dead cells, most of the cells would be in interphase because they are actively preparing for division. Meiosis is a type of cell division that occurs in reproductive cells to produce gametes, not in the intestinal epithelium. Mitosis is a type of cell division that occurs in somatic cells, but it is a relatively short phase compared to interphase. Condensed chromatin is a characteristic of cells undergoing division, but not all cells in the population would be in this state. Therefore, the correct answer is that most of the cells would be in interphase.

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  • 7. 

    A cell cycle consists of 

    • A.

      Mitosis and meiosis

    • B.

      G1, the S phase, and G2

    • C.

      Prophase, metaphase, anaphase, and telophase.

    • D.

      Interphase and mitosis.

    • E.

      Meiosis and fertilization.

    Correct Answer
    D. Interphase and mitosis.
    Explanation
    The correct answer is interphase and mitosis. The cell cycle is the sequence of events that occurs in a cell leading to its division into two daughter cells. Interphase is the longest phase of the cell cycle and includes three subphases: G1, S, and G2. During interphase, the cell grows, replicates its DNA, and prepares for division. Mitosis is the phase of the cell cycle where the nucleus divides into two identical daughter nuclei. It consists of four stages: prophase, metaphase, anaphase, and telophase. Therefore, the correct answer is interphase and mitosis, as these are the two main phases of the cell cycle.

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  • 8. 

    The initiation of the S phase and teh M phase of the cell cycle depends on a pair of biochemicals called ____ and ____.

    • A.

      Actin; myosin

    • B.

      Cdk's; cyclin

    • C.

      Ligand; receptor

    • D.

      MSH; MSH-receptor

    • E.

      ATP; ATPase

    Correct Answer
    B. Cdk's; cyclin
    Explanation
    The initiation of the S phase and the M phase of the cell cycle depends on a pair of biochemicals called Cdk's and cyclin. Cdk's, or cyclin-dependent kinases, are a group of enzymes that regulate the progression of the cell cycle. They become active when they bind to cyclin proteins, which are also involved in controlling the cell cycle. Together, Cdk's and cyclin play a crucial role in coordinating the events of the S phase and the M phase, ensuring that DNA replication and cell division occur at the appropriate times.

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  • 9. 

    During mitosis and meiosis the chromatin compacts.  Which of teh following processe3s takes place more easily because this compaction?

    • A.

      The orderly distribution of genetic material to two new nuclei

    • B.

      Teh replication of the DNA

    • C.

      Exposing the genetic information on the DNA

    • D.

      The unwinding of DNA from around the histones

    • E.

      The disappearance of the nuclear membrane

    Correct Answer
    A. The orderly distribution of genetic material to two new nuclei
    Explanation
    During mitosis and meiosis, the chromatin compacts to form chromosomes. This compaction allows for the orderly distribution of genetic material to two new nuclei. When the chromatin is compacted into chromosomes, it becomes easier for the cell to separate and distribute the genetic material evenly between the two daughter cells. This ensures that each new cell receives the correct number and type of chromosomes, maintaining the genetic integrity of the organism.

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  • 10. 

    When dividing cells are examined under a light microscope, chromosomes first become visible during

    • A.

      Interphase.

    • B.

      The S phase.

    • C.

      Prophase.

    • D.

      G1.

    • E.

      G2.

    Correct Answer
    C. Prophase.
    Explanation
    During prophase, the chromosomes condense and become visible under a light microscope. This is the first stage of mitosis, where the nuclear envelope breaks down and the spindle apparatus forms. In interphase, the cell is not actively dividing, and the chromosomes are not visible. The S phase is a part of interphase where DNA replication occurs. G1 and G2 are also phases of interphase where the cell prepares for DNA replication and cell division, respectively. Therefore, prophase is the correct answer as it is the stage where chromosomes become visible.

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  • 11. 

    The structures that line up the chromatids on the equatorial plate during metaphase are called

    • A.

      Asters.

    • B.

      Polar and kinetochore microtubules

    • C.

      Centrosomes.

    • D.

      Centrioles.

    • E.

      Histones.

    Correct Answer
    B. Polar and kinetochore microtubules
    Explanation
    During metaphase, the chromosomes align themselves along the equatorial plate of the cell. This alignment is facilitated by structures called polar and kinetochore microtubules. The polar microtubules extend from opposite poles of the cell and help to maintain the separation of the poles, while the kinetochore microtubules attach to the kinetochores of the chromosomes and play a crucial role in pulling the chromosomes towards the equatorial plate. Therefore, the polar and kinetochore microtubules are responsible for the proper alignment of the chromatids during metaphase.

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  • 12. 

    The microtubules of teh mitotic spindle attach to a specialized structure in the centromere region of each chromosome called the

    • A.

      Kinetochore.

    • B.

      Nucleosome.

    • C.

      Equatorial plate.

    • D.

      Aster.

    • E.

      Centrosome.

    Correct Answer
    A. Kinetochore.
    Explanation
    During mitosis, the microtubules of the mitotic spindle connect to a specific structure in the centromere region of each chromosome known as the kinetochore. The kinetochore plays a crucial role in ensuring accurate chromosome segregation during cell division. It helps to align and separate the chromosomes by attaching to the microtubules and exerting force to move them towards opposite poles of the cell. This process is essential for the equal distribution of genetic material to the daughter cells.

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  • 13. 

    After the centromeres separate during mitosis, the chromatids, now called ____, move toward opposite poles of the spindle.

    • A.

      Centrosomes

    • B.

      Kinetochores

    • C.

      Half-spindles

    • D.

      Asters

    • E.

      Daughter chromosomes

    Correct Answer
    E. Daughter chromosomes
    Explanation
    After the centromeres separate during mitosis, the chromatids, now called daughter chromosomes, move toward opposite poles of the spindle. This is because the centromeres hold the sister chromatids together, and when they separate, each chromatid becomes an individual chromosome. These daughter chromosomes are then pulled towards opposite poles of the spindle by the spindle fibers, ensuring equal distribution of genetic material to the daughter cells.

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  • 14. 

    During mitotic anaphase, chromatids migrate

    • A.

      From the poles of the cell toward the mtaphase plate.

    • B.

      From the metaphase plate toward the poles.

    • C.

      Toward teh nuclear envelope.

    • D.

      Along with teir sister chromatids toward one pole.

    • E.

      Along with the other member of the homologous pair toward the metaphase plate.

    Correct Answer
    B. From the metaphase plate toward the poles.
    Explanation
    During mitotic anaphase, chromatids migrate from the metaphase plate toward the poles of the cell. This is a crucial step in cell division where the sister chromatids, which were previously aligned at the metaphase plate, separate and move towards opposite ends of the cell. This movement is facilitated by the shortening of microtubules attached to the kinetochores of the chromatids. As the microtubules shorten, the chromatids are pulled towards the poles, ultimately leading to the formation of two daughter cells with identical genetic material.

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  • 15. 

    At the milestone that defines metaphase, the chromosomes

    • A.

      Separate.

    • B.

      Come together.

    • C.

      Are at opposite poles.

    • D.

      Line up at the equatorial plate.

    • E.

      Cross over.

    Correct Answer
    D. Line up at the equatorial plate.
    Explanation
    During metaphase, the chromosomes align themselves along the equatorial plate of the cell. This alignment is crucial for the subsequent separation of the chromosomes during anaphase. The equatorial plate ensures that each daughter cell receives an equal and complete set of chromosomes. Therefore, the correct answer is "line up at the equatorial plate."

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  • 16. 

    The sizes and shapes of chromosomes can be observed most easily in a cell that is in

    • A.

      Prophase.

    • B.

      Metaphase.

    • C.

      Anaphase.

    • D.

      Telophase.

    • E.

      Cytokinesis.

    Correct Answer
    B. Metaphase.
    Explanation
    During metaphase, the chromosomes align themselves along the equatorial plane of the cell. This alignment allows for a clear and organized view of the sizes and shapes of the chromosomes. In prophase, the chromosomes are condensed and not yet aligned. Anaphase and telophase are stages where the chromosomes are moving and separating, making it difficult to observe their sizes and shapes. Cytokinesis is the final stage of cell division and does not involve the observation of chromosomes.

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  • 17. 

    At the milestone that defines telophase, the chromosomes

    • A.

      Separate.

    • B.

      Come together.

    • C.

      Are at opposite poles.

    • D.

      Line up.

    • E.

      Cross over.

    Correct Answer
    C. Are at opposite poles.
    Explanation
    At the milestone that defines telophase, the chromosomes are at opposite poles. Telophase is the final stage of mitosis, where the duplicated chromosomes have reached opposite ends of the cell. This is achieved through the action of spindle fibers, which pull the chromosomes towards their respective poles. During telophase, the nuclear envelope reforms around each set of chromosomes, and the chromosomes begin to decondense. Eventually, two separate nuclei will form, marking the completion of cell division. Therefore, the correct answer is "are at opposite poles."

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  • 18. 

    Chromosomes "decondense" into diffuse chromatin

    • A.

      At the end of telophase

    • B.

      At the beginning of prophase.

    • C.

      At the end of interphase.

    • D.

      At the end of metaphase.

    • E.

      Only in dying cells.

    Correct Answer
    A. At the end of telophase
    Explanation
    At the end of telophase, chromosomes decondense into diffuse chromatin. Telophase is the final stage of mitosis, where the separated sister chromatids reach opposite poles of the cell. During telophase, the nuclear envelope reforms around the chromosomes, and the chromosomes start to unwind and decondense. This decondensation allows the genetic material to become more accessible for gene expression and other cellular processes. Therefore, at the end of telophase is when chromosomes decondense into diffuse chromatin.

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  • 19. 

    In plant cells, cytokinesis is accomplished by the formation of a(n)

    • A.

      Aster.

    • B.

      Membrane furrow.

    • C.

      Equatorial plate.

    • D.

      Cell plate.

    • E.

      Spindle.

    Correct Answer
    D. Cell plate.
    Explanation
    In plant cells, cytokinesis is accomplished by the formation of a cell plate. During cytokinesis, the cell plate forms in the middle of the dividing cell, eventually developing into a new cell wall that separates the two daughter cells. This process is unique to plant cells, as animal cells typically undergo cytokinesis through the formation of a cleavage furrow. The cell plate allows for the successful division of plant cells and the formation of new cell walls, enabling the growth and development of plants.

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  • 20. 

    The major drawback of asexual reproduction is that it

    • A.

      Takes a great deal of time

    • B.

      Generates variation

    • C.

      Prevents change.

    • D.

      Requires cytokinesis.

    • E.

      Produces a lack of variation among the progeny.

    Correct Answer
    E. Produces a lack of variation among the progeny.
    Explanation
    Asexual reproduction produces offspring that are genetically identical to the parent, resulting in a lack of variation among the progeny. This lack of genetic diversity can be a major drawback because it reduces the ability of the population to adapt to changing environments or to overcome new challenges. Without genetic variation, the offspring may be more susceptible to diseases or less able to survive in different conditions. In contrast, sexual reproduction allows for the mixing of genetic material from two parents, resulting in offspring with greater genetic diversity and a better chance of survival in changing environments.

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  • 21. 

    A haploid cell is a cell

    • A.

      In which the genes are arranged haphazardly.

    • B.

      Containing only one copy of each chromosome.

    • C.

      That has resulted from the process of mitosis.

    • D.

      With twice the number of chromosomes

    • E.

      None of the above.

    Correct Answer
    B. Containing only one copy of each chromosome.
    Explanation
    A haploid cell is a cell containing only one copy of each chromosome. This means that it has half the number of chromosomes compared to a diploid cell, which contains two copies of each chromosome. Haploid cells are typically found in reproductive cells, such as sperm and eggs, and are involved in sexual reproduction. In contrast, somatic cells in the body are usually diploid. The arrangement of genes in a cell is not related to whether it is haploid or diploid, so the option "in which the genes are arranged haphazardly" is incorrect. The other options, "that has resulted from the process of mitosis" and "with twice the number of chromosomes," are also incorrect as they do not accurately describe haploid cells.

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  • 22. 

    Sexual reproduction increase genetic variability through

    • A.

      The exchange of genetic information between male and female gaetes during eiosis I.

    • B.

      The random separation of homologous chromosomes.

    • C.

      The union of male and female gametes.

    • D.

      Crossing over, independent assortment,a nd random fertilization

    • E.

      Random assortment of male and female chromosomes.

    Correct Answer
    D. Crossing over, independent assortment,a nd random fertilization
    Explanation
    Sexual reproduction increases genetic variability through three main processes: crossing over, independent assortment, and random fertilization. Crossing over occurs during meiosis I when homologous chromosomes exchange genetic material, resulting in new combinations of alleles. Independent assortment refers to the random alignment and separation of homologous chromosomes during meiosis I, leading to different combinations of maternal and paternal chromosomes in gametes. Finally, random fertilization occurs when any sperm can fertilize any egg, resulting in a random combination of genetic material from two different individuals. These processes contribute to the creation of genetically diverse offspring.

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  • 23. 

    Diploid cells of the fruit fly Drosophila have ten chromosomes. How many chromosomes does a Drosophila gamete have?

    • A.

      One

    • B.

      Two

    • C.

      Five

    • D.

      Ten

    • E.

      Twenty

    Correct Answer
    C. Five
    Explanation
    A diploid cell contains two sets of chromosomes, while a gamete is a haploid cell that contains only one set of chromosomes. Since diploid cells of Drosophila have ten chromosomes, a Drosophila gamete would have half that number, which is five chromosomes. Therefore, the correct answer is five.

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  • 24. 

    Each diploid cell of a human female contains ____ of each type of chromosome.

    • A.

      One

    • B.

      Two

    • C.

      Four

    • D.

      A total of 23

    • E.

      A total of 46

    Correct Answer
    B. Two
    Explanation
    Each diploid cell of a human female contains two of each type of chromosome. This is because humans have a diploid number of chromosomes, which means they have two sets of chromosomes, one inherited from each parent. In a female, the two sets of chromosomes include one set of sex chromosomes (XX) and one set of autosomes (non-sex chromosomes). Therefore, each diploid cell contains two copies of each type of chromosome.

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  • 25. 

    Which of the following statements about homologous chromosome pairs is false?

    • A.

      They come from only one of the individual's parents.

    • B.

      They usually contain slightly different versions of the same gtenetic information.

    • C.

      They separate from each other during meiosis I

    • D.

      They synapse during meiosis I

    • E.

      Each contains two sister chromatids at the beginning of the meiosis I

    Correct Answer
    A. They come from only one of the individual's parents.
    Explanation
    Homologous chromosome pairs do not come from only one of the individual's parents. In fact, homologous chromosomes are derived from both parents, with one chromosome in each pair coming from the mother and the other from the father. This is because during sexual reproduction, an individual inherits one set of chromosomes from each parent, resulting in a pair of homologous chromosomes. Thus, the statement that they come from only one of the individual's parents is false.

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  • 26. 

    Human males have ____ sex chromosomes.

    • A.

      XX

    • B.

      XY

    • C.

      XO

    • D.

      Three types of

    • E.

      23

    Correct Answer
    B. XY
    Explanation
    Human males have XY sex chromosomes. In humans, sex is determined by the presence or absence of the Y chromosome. Males have one X and one Y chromosome, while females have two X chromosomes. The combination of XY determines the development of male reproductive organs and secondary sexual characteristics.

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  • 27. 

    During meiosis, the sister chromatids separate during

    • A.

      Anaphase II.

    • B.

      Anaphase I.

    • C.

      The S phase.

    • D.

      Synapsis.

    • E.

      Telophase II.

    Correct Answer
    A. Anaphase II.
    Explanation
    During meiosis, the sister chromatids separate during anaphase II. This is the stage of meiosis where the sister chromatids, which are still connected by a centromere, are pulled apart towards opposite poles of the cell. This separation ensures that each resulting daughter cell receives one copy of each chromosome. Anaphase I, on the other hand, is when the homologous chromosomes separate. The S phase is the phase of the cell cycle where DNA replication occurs. Synapsis is the pairing of homologous chromosomes during prophase I. Telophase II is the final stage of meiosis where the nuclear envelope reforms around the separated sister chromatids.

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  • 28. 

    The processes of synapsis and the formation of chiasmata

    • A.

      Involve reciprocal exchange of chromosomal sections.

    • B.

      Involve the recombination of DNA on homologous chromosomes.

    • C.

      Bring about an increase in genetic variation.

    • D.

      provide evidence that an exchange of genetic material has occurred.

    • E.

      All of the above.

    Correct Answer
    E. All of the above.
    Explanation
    The processes of synapsis and the formation of chiasmata involve the reciprocal exchange of chromosomal sections, which is known as recombination. This recombination of DNA on homologous chromosomes brings about an increase in genetic variation. Furthermore, the formation of chiasmata provides evidence that an exchange of genetic material has occurred. Therefore, all of the given options are correct.

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  • 29. 

    The exchange of genetic material between chromatids on homologous chromosomes occurs during

    • A.

      Interphase.

    • B.

      Mitosis and meiosis.

    • C.

      Prophase I.

    • D.

      Anaphase I.

    • E.

      Anaphase II.

    Correct Answer
    C. Prophase I.
    Explanation
    During prophase I of meiosis, homologous chromosomes pair up and exchange genetic material through a process called crossing over. This exchange of genetic material between chromatids on homologous chromosomes increases genetic diversity and is a crucial step in meiosis. Therefore, the correct answer is prophase I.

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  • 30. 

    The number of chromosomes is reduced to half during

    • A.

      Anaphase of mitosis and meiosis.

    • B.

      Meiosis Ii.

    • C.

      Meiosis I.

    • D.

      Fertilization.

    • E.

      Interphase.

    Correct Answer
    C. Meiosis I.
    Explanation
    During meiosis I, the number of chromosomes is reduced to half. This is because meiosis I involves two rounds of cell division, resulting in the separation of homologous chromosomes. In the first division, known as meiosis I, homologous chromosomes pair up and exchange genetic material through a process called crossing over. Then, these homologous chromosomes separate, resulting in two daughter cells with half the number of chromosomes as the parent cell. Therefore, meiosis I is the correct answer as it is the specific stage where the reduction in chromosome number occurs.

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  • 31. 

    Accidents during meiosis that can result in trisomies and monosomies are called

    • A.

      Nondisjuncitons.

    • B.

      Inversions.

    • C.

      Reciprocal translocations.

    • D.

      Recombinations.

    • E.

      Acrocentricities.

    Correct Answer
    A. Nondisjuncitons.
    Explanation
    Accidents during meiosis that can result in trisomies and monosomies are called nondisjunctions. Nondisjunction occurs when chromosomes fail to separate properly during cell division, leading to an unequal distribution of chromosomes in the resulting cells. This can result in the formation of gametes with an extra chromosome (trisomy) or a missing chromosome (monosomy). Nondisjunction can occur in both sex chromosomes and autosomes, and it is a common cause of genetic disorders such as Down syndrome.

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  • 32. 

    The fact that most monosomies and trisomies are lethal to human embryos illustrates the

    • A.

      Importance of the orderly distribution of genetic material during meiosis.

    • B.

      Exchange of genetic information during crossing over.

    • C.

      Advantage of sexual reproduction to the survival of a population.

    • D.

      Fact that each chromosome contains a single molecule of DNA.

    • E.

      Formation of haploid gametes as a result of meiosis.

    Correct Answer
    A. Importance of the orderly distribution of genetic material during meiosis.
    Explanation
    The fact that most monosomies and trisomies are lethal to human embryos suggests that the orderly distribution of genetic material during meiosis is crucial. Meiosis is the process by which gametes are formed, and any errors in the distribution of chromosomes can result in genetic abnormalities. This underscores the importance of meiosis in maintaining the correct number of chromosomes in offspring and ensuring their viability.

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  • 33. 

    One difference between mitosis and meiosis I is that 

    • A.

      Homologous chromosome pairs synapse during mitosis.

    • B.

      Chromosomes do not replicate in the interphase preseding meiosis.

    • C.

      Homologoous chromosome pairs synapse during meiosis but not during mitosis.

    • D.

      Spindles composed of microtubules are not required during meiosis.

    • E.

      Sister chromatids separate during meiosis but not during mitosis.

    Correct Answer
    C. Homologoous chromosome pairs synapse during meiosis but not during mitosis.
    Explanation
    During meiosis, homologous chromosome pairs synapse, meaning they come together and align with each other. This allows for crossing over of genetic material between the homologous chromosomes, resulting in genetic variation. In mitosis, however, homologous chromosome pairs do not synapse. Instead, sister chromatids separate, resulting in two identical daughter cells. Therefore, the correct answer is that homologous chromosome pairs synapse during meiosis but not during mitosis.

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  • 34. 

    Many chromosome abnormalities (trisomies and menosomies) are not observed in teh human population because

    • A.

      They are lethal and cause spontaneous abortion of the embryo early in development.

    • B.

      All trisomies and monosomies are lethal early in childhood.

    • C.

      Meiosis distributes chromosomes to daughter cells with great precision.

    • D.

      They are so difficult to count.

    • E.

      the human meiotic spindle is self-correcting

    Correct Answer
    A. They are lethal and cause spontaneous abortion of the embryo early in development.
    Explanation
    Chromosome abnormalities such as trisomies and monosomies are not observed in the human population because they are lethal and cause spontaneous abortion of the embryo early in development. This means that when these abnormalities occur, the embryo is unable to develop properly and is naturally terminated, preventing the abnormality from being passed on to future generations.

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  • 35. 

    The process of programmed cell death is called 

    • A.

      Necreosis.

    • B.

      Lysis.

    • C.

      Apoptosis.

    • D.

      Cell displacement.

    • E.

      Cellular suicide.

    Correct Answer
    C. Apoptosis.
    Explanation
    Apoptosis is the correct answer because it refers to the process of programmed cell death. This process is crucial for maintaining tissue homeostasis and eliminating damaged or unnecessary cells. Unlike necreosis, which is not a recognized term, apoptosis is a well-defined and extensively studied mechanism. Lysis refers to the breaking down of cells, but it does not specifically refer to programmed cell death. Cell displacement and cellular suicide are not accurate terms to describe programmed cell death.

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  • 36. 

    If two strains of true-breeding plants that have different alleles for a certain character are crossed, their progeny are called

    • A.

      The P generation

    • B.

      The F1 generation

    • C.

      The F2 generation

    • D.

      F1 crosses.

    • E.

      F2 progeny

    Correct Answer
    B. The F1 generation
    Explanation
    When two strains of true-breeding plants with different alleles for a specific trait are crossed, their offspring are called the F1 generation. The F1 generation represents the first filial generation and consists of hybrids that inherit one allele from each parent. These hybrids usually display a combination of traits from both parents.

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  • 37. 

    Mendel's crossing of spherical-seeded pea plants with wrinkled-seeded pea plants resulted in progeny that all had spherical seeds.  This indicates that the wrinkled-seed trait is

    • A.

      Codominant.

    • B.

      Dominant.

    • C.

      Recessive.

    • D.

      Both a and b

    • E.

      Both a and c

    Correct Answer
    C. Recessive.
    Explanation
    When Mendel crossed spherical-seeded pea plants with wrinkled-seeded pea plants and obtained progeny with only spherical seeds, it suggests that the spherical-seed trait is dominant over the wrinkled-seed trait. This means that the offspring inherited the dominant spherical-seed allele from one parent and the recessive wrinkled-seed allele from the other parent. As a result, the recessive wrinkled-seed trait was not expressed in the offspring, indicating that it is a recessive trait.

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  • 38. 

    The physical appearance of a character is called

    • A.

      The genotype

    • B.

      The phenotype.

    • C.

      An allele

    • D.

      A trait

    • E.

      A gene.

    Correct Answer
    B. The phenotype.
    Explanation
    The physical appearance of a character is referred to as the phenotype. This term encompasses the observable traits or characteristics of an organism, such as its hair color, eye color, height, and so on. The phenotype is determined by the interaction of an organism's genotype (its genetic makeup) with environmental factors. Genotype refers to the specific combination of alleles (different forms of a gene) that an organism carries, while an allele is one of the variant forms of a gene. A gene, on the other hand, is a segment of DNA that contains the instructions for building a specific protein or performing a particular function.

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  • 39. 

    Different forms of a gene are called

    • A.

      Traits

    • B.

      Phenotypes

    • C.

      Genotypes

    • D.

      Alleles

    • E.

      None of the above

    Correct Answer
    D. Alleles
    Explanation
    Alleles are different forms of a gene that exist within a population. They are responsible for the variation in traits or characteristics observed among individuals. Each individual inherits two alleles for each gene, one from each parent. The combination of alleles determines the genotype, which in turn influences the phenotype or observable traits of an organism. Therefore, alleles are the correct term to describe the different forms of a gene.

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  • 40. 

    The site on the chromosome occupied by a gene is called a(n)

    • A.

      Allele

    • B.

      Region

    • C.

      Locus

    • D.

      Type

    • E.

      Phenotype

    Correct Answer
    C. Locus
    Explanation
    A locus refers to the specific site or position on a chromosome where a gene is located. It is the physical location where genetic information is found. Therefore, the correct answer is locus.

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  • 41. 

    A particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait is referred to as a 

    • A.

      Parental cross.

    • B.

      Dihybrid cross.

    • C.

      Filial generation mating.

    • D.

      Reciprocal cross.

    • E.

      Test cross.

    Correct Answer
    E. Test cross.
    Explanation
    A test cross is a particular genetic cross in which the individual in question is crossed with an individual known to be homozygous for a recessive trait. This cross is performed to determine the genotype of the individual in question. By observing the phenotypes of the offspring, one can determine whether the individual is homozygous dominant or heterozygous for the trait in question. The test cross allows for the determination of the unknown genotype by crossing it with a known genotype.

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  • 42. 

    A pea plant with red flowers is test crossed, and one half of the resulting progeny have red flowers, while the other half has white flowers.  Therefore, the genotype of the test-crossed parent was 

    • A.

      RR.

    • B.

      Rr.

    • C.

      Rr.

    • D.

      Either RR or Rr.

    • E.

      This cannot be answered without more information.

    Correct Answer
    B. Rr.
    Explanation
    The test-crossed parent must have the genotype Rr. This is because when a pea plant with red flowers is test crossed (crossed with a homozygous recessive individual), half of the resulting progeny will have the same phenotype as the test-crossed parent (red flowers) and the other half will have the phenotype of the recessive parent (white flowers). If the test-crossed parent had the genotype RR, then all of the progeny would have red flowers. Therefore, the only possible genotype for the test-crossed parent is Rr.

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  • 43. 

    A dihybrid cross

    • A.

      Results in a genotypic ration of 2:1.

    • B.

      Involves genes located on the sex chromosomes.

    • C.

      Results in offspring of lower quality than that of the parents

    • D.

      Results in two different phenotypes in the F2 generation

    • E.

      Is a cross between identical double heterozygotes.

    Correct Answer
    E. Is a cross between identical double heterozygotes.
    Explanation
    A dihybrid cross is a breeding experiment that involves the crossing of two individuals who are heterozygous for two different traits. In this case, the answer states that it is a cross between identical double heterozygotes. This means that both parents have the same two heterozygous alleles for the traits being studied. This type of cross allows for the observation of the inheritance patterns of both traits simultaneously.

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  • 44. 

    Mendel's dihybrid crosses

    • A.

      Resulted in four different phenotypes.

    • B.

      Produced recombinant phenotypes.

    • C.

      Lead to the formation of the law of independent assortment.

    • D.

      involved genes located on separate chromosomes.

    • E.

      All of the above.

    Correct Answer
    E. All of the above.
    Explanation
    The given answer, "All of the above," is correct because Mendel's dihybrid crosses resulted in four different phenotypes, produced recombinant phenotypes, lead to the formation of the law of independent assortment, and involved genes located on separate chromosomes. This means that all of these statements are true and accurately describe the outcomes of Mendel's dihybrid crosses.

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  • 45. 

    Despite the law of independent assortment, when two loci are on the same chromosome, the phenotypes of the progeny sometimes do not fit the predicted phenotypes due to

    • A.

      Translocation.

    • B.

      Inversions.

    • C.

      Chromatid affinities

    • D.

      Linkage.

    • E.

      reciprocal chromosomal exchanges.

    Correct Answer
    D. Linkage.
    Explanation
    When two loci are on the same chromosome, they are said to be linked. This means that the genes at these loci tend to be inherited together rather than independently assorting. Linkage occurs because the loci are physically close to each other on the same chromosome, making it less likely for them to be separated during crossing over. As a result, the phenotypes of the progeny may not fit the predicted phenotypes based on independent assortment. Therefore, the correct answer is "linkage."

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  • 46. 

    Genetic mutations are

    • A.

      Rare

    • B.

      Stable

    • C.

      Inherited changes in DNA.

    • D.

      Random

    • E.

      All of the above

    Correct Answer
    E. All of the above
    Explanation
    Genetic mutations can occur randomly and are considered rare events. They can also be stable, meaning that they persist over time and are passed on to future generations. Additionally, genetic mutations can be inherited, meaning they are passed from parents to their offspring. Therefore, the correct answer is "All of the above."

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  • 47. 

    If the same allele has two or more phenotypic effects, it is said to be

    • A.

      Codominant.

    • B.

      A marker.

    • C.

      Linked.

    • D.

      Pleiotropic.

    • E.

      Hemizygous.

    Correct Answer
    D. Pleiotropic.
    Explanation
    When the same allele has multiple phenotypic effects, it is referred to as pleiotropic. Pleiotropy occurs when a single gene influences multiple traits or characteristics. This can happen because the gene product is involved in multiple biochemical pathways or has multiple functions within the cell. The effects of pleiotropy can be observed in various genetic disorders and traits, where a mutation in a single gene can lead to multiple symptoms or traits. Therefore, in this case, the correct answer is pleiotropic.

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  • 48. 

    How many autosomes do humans have?

    • A.

      23 pairs

    • B.

      22 pairs

    • C.

      1 pair

    • D.

      45

    • E.

      16

    Correct Answer
    B. 22 pairs
    Explanation
    Humans have 22 pairs of autosomes. Autosomes are the non-sex chromosomes, meaning they are not involved in determining the sex of an individual. Humans have a total of 23 pairs of chromosomes, with one pair being the sex chromosomes (XX in females and XY in males) and the remaining 22 pairs being autosomes.

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  • 49. 

    What is the pattern of inheritance for a rare dominant allele?

    • A.

      Every affected person has an affected parent.

    • B.

      Unaffected parents can produce children who are affected.

    • C.

      Unaffected mothers have affected sons and daughters who are carriers.

    • D.

      None of the above.

    Correct Answer
    A. Every affected person has an affected parent.
    Explanation
    The pattern of inheritance for a rare dominant allele is that every affected person has an affected parent. This means that if an individual has the rare dominant allele and displays the associated trait or condition, at least one of their parents must also have the allele and display the trait. This pattern follows the principle that a dominant allele will be expressed in the phenotype even if only one copy is present.

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  • 50. 

    What fraction of offspring of the cross AaBb x AaBb is homozygous for all the dominant alleles, assuming that they are on different chromosomes?

    • A.

      1/4

    • B.

      1/8

    • C.

      1/16

    • D.

      1/32

    • E.

      1/64

    Correct Answer
    C. 1/16
    Explanation
    When two individuals with the genotype AaBb are crossed, they can produce offspring with four different combinations of alleles: AB, Ab, aB, and ab. Out of these four combinations, only one combination (AB) has both dominant alleles. This means that there is a 1/4 chance of any individual offspring having the AB combination. However, since the question asks for the fraction of offspring that are homozygous for all dominant alleles, we need to square this fraction. Therefore, the correct answer is 1/4 * 1/4 = 1/16.

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  • Mar 16, 2023
    Quiz Edited by
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  • May 10, 2010
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