Bio Test 3 (Part 2)

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Biology Quizzes & Trivia

Bio test part 2 of 5.55 question test.


Questions and Answers
  • 1. 

    Repressor proteins

    • A.

      Prevent binding of RNA polymerase to DNA.

    • B.

      Cause the DNA regions that contain the operator to twist or loop.

    • C.

      Inactivate operon genes when their products are not required.

    • D.

      Bind to sets of operators.

    • E.

      All of these.

    Correct Answer
    E. All of these.
    Explanation
    Repressor proteins can prevent the binding of RNA polymerase to DNA, causing a blockage in gene transcription. They can also cause the DNA regions that contain the operator to twist or loop, further inhibiting gene expression. Additionally, repressor proteins can inactivate operon genes when their products are not required, regulating gene expression based on the needs of the cell. Finally, repressor proteins bind to sets of operators, allowing them to control the expression of multiple genes simultaneously. Therefore, all of these statements accurately describe the functions of repressor proteins.

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  • 2. 

    The obvious advantage of the lactose operon is that

    • A.

      It allows bacteria to survive in the presence of lactose.

    • B.

      Lactose-metabolizing enzymes need not be made when lactose is not present.

    • C.

      It enables bacteria to make lactose only in the presence of the proper enzymes.

    • D.

      It negates the need for milk in the diet of adult humans.

    • E.

      It enables glucose to substitute for lactose in the diet of lactose intolerant persons.

    Correct Answer
    B. Lactose-metabolizing enzymes need not be made when lactose is not present.
    Explanation
    The lactose operon allows bacteria to regulate the production of lactose-metabolizing enzymes based on the presence or absence of lactose. When lactose is not present, the operon prevents the unnecessary production of these enzymes, conserving energy and resources for the bacteria. This regulation ensures that lactose-metabolizing enzymes are only made when lactose is available, allowing bacteria to efficiently utilize lactose as a source of energy and survive in its presence.

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  • 3. 

    Which of the following accounts for the negative control of operons?

    • A.

      Promoters

    • B.

      Repressors

    • C.

      Structural genes

    • D.

      Operators

    • E.

      All of these

    Correct Answer
    B. Repressors
    Explanation
    The negative control of operons is achieved through the action of repressors. Repressors are proteins that bind to the operator region of the operon and prevent the transcription of the structural genes. By binding to the operator, repressors physically block the RNA polymerase from binding to the promoter region, thereby inhibiting gene expression. This negative control mechanism allows for regulation and control of gene expression in response to various environmental cues or signals.

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  • 4. 

    The positive control of the lactose operon in bacteria is

    • A.

      Activated by a repressor protein.

    • B.

      Independent of glucose concentration.

    • C.

      Activated by the CAP.

    • D.

      Regulated by RNA polymerase.

    • E.

      All of these.

    Correct Answer
    C. Activated by the CAP.
    Explanation
    The positive control of the lactose operon in bacteria is activated by the CAP. The CAP (catabolite activator protein) binds to a specific site on the DNA called the CAP site, which is located upstream of the promoter region of the lactose operon. When glucose levels are low, cAMP (cyclic AMP) levels increase, and cAMP binds to the CAP protein, causing a conformational change that allows the CAP protein to bind to the CAP site. This binding of CAP to the CAP site enhances the binding of RNA polymerase to the promoter region, leading to increased transcription of the lactose operon genes. Therefore, the CAP protein plays a crucial role in activating the lactose operon in the presence of low glucose levels.

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  • 5. 

    Refer to Figure 15-3 to answer the following questions.As a result of the action illustrated in the figure,

    • A.

      Structural genes are transcribed.

    • B.

      Lactose is broken down.

    • C.

      The lactose operon is repressed.

    • D.

      The regulatory gene is inactivated.

    • E.

      Lactose production is enhanced.

    Correct Answer
    C. The lactose operon is repressed.
    Explanation
    Based on the given information, the figure likely shows a mechanism where the lactose operon is repressed. This means that the genes involved in the lactose operon are not being transcribed or expressed. This repression could be due to the presence of a repressor protein that binds to the operator region of the operon, preventing transcription. This repression would result in the downregulation of lactose production.

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  • 6. 

    Lamarck's contribution to the theory of evolution is the concept of

    • A.

      Natural selection.

    • B.

      Catastrophism.

    • C.

      Inheritance of acquired characteristics.

    • D.

      Mutation.

    • E.

      Geographic distribution of organisms.

    Correct Answer
    C. Inheritance of acquired characteristics.
    Explanation
    Lamarck's contribution to the theory of evolution is the concept of inheritance of acquired characteristics. According to Lamarck, organisms can acquire new traits during their lifetime as a response to their environment, and these acquired traits can be passed on to their offspring. This idea suggests that traits acquired through an organism's lifetime can lead to evolutionary change in a population over time. However, this concept has been largely discredited by modern genetics, as it contradicts the principles of inheritance discovered by Gregor Mendel.

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  • 7. 

    Which of the following would be a modern example of Lamarckianism?

    • A.

      A strain of houseflies resistant to insecticides emerges.

    • B.

      Squirrels separated by a river are found to be unable to interbreed.

    • C.

      A son is born with a portion of his right index finger missing, the same portion severed from his father's hand in an accident.

    • D.

      A strain of houseflies resistant to insecticides emerges; and squirrels separated by a river are found to be unable to interbreed.

    • E.

      A strain of houseflies resistant to insecticides emerges; and squirrels separated by a river are found to be unable to interbreed; and a son is born with a portion of his right index finger missing, the same portion severed from his father's hand in an accident.

    Correct Answer
    C. A son is born with a portion of his right index finger missing, the same portion severed from his father's hand in an accident.
    Explanation
    This answer is a modern example of Lamarckianism because it suggests that an acquired trait, in this case, the missing portion of the finger, can be passed on to the next generation. Lamarckianism is a theory that proposes that traits acquired during an organism's lifetime can be inherited by its offspring. In this scenario, the father lost a portion of his finger in an accident, and the son is born with the same missing portion, implying that the injury somehow influenced the genetic makeup of the son.

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  • 8. 

    Galapagos finches are examples of

    • A.

      Scavengers.

    • B.

      Morphological isolation.

    • C.

      Adaptive radiation.

    • D.

      Punctuated equilibrium.

    • E.

      The inheritance of acquired characteristics.

    Correct Answer
    C. Adaptive radiation.
    Explanation
    Galapagos finches are examples of adaptive radiation because they have evolved from a common ancestor into different species, each with unique adaptations to different ecological niches on the Galapagos Islands. This process of adaptive radiation allows species to diversify and occupy various habitats, leading to the development of new species with specialized traits. The finches' beak shapes, for example, have adapted to different food sources, such as seeds, insects, or nectar, enabling them to survive and reproduce in their respective environments.

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  • 9. 

    Natural selection operates to produce changes in

    • A.

      Individuals.

    • B.

      Populations.

    • C.

      Kingdoms.

    • D.

      Phyla.

    • E.

      Animals only.

    Correct Answer
    B. Populations.
    Explanation
    Natural selection is a process by which certain traits become more or less common in a population over time. It acts on the variation within a population and favors individuals with advantageous traits, allowing them to survive and reproduce more successfully. Therefore, natural selection operates on populations, as it leads to changes in the genetic makeup of a group of individuals rather than changes within individual organisms.

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  • 10. 

    One part of Darwin's theory is that individuals with certain traits have an increased competitive edge. The source of these traits is

    • A.

      Adaptation to the stress.

    • B.

      Development over a lifetime.

    • C.

      Inheritance at conception.

    • D.

      Mutation after birth.

    • E.

      All of these.

    Correct Answer
    C. Inheritance at conception.
    Explanation
    Darwin's theory suggests that individuals with certain traits have a competitive advantage. These traits are believed to be inherited at the time of conception. This means that individuals receive these traits from their parents through the passing on of genetic material. The theory does not suggest that these traits are a result of adaptation to stress or development over a lifetime. While mutations can occur after birth, they are not the primary source of these advantageous traits. Therefore, the correct answer is inheritance at conception.

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  • 11. 

    The operation of natural selection depends upon the fact that

    • A.

      The strong always survive, whereas the weak always die.

    • B.

      Some individuals have a better chance to produce more offspring.

    • C.

      Mutations are always harmful.

    • D.

      Acquired characteristics are inherited.

    • E.

      Reproduction of all members of a species is virtually the same.

    Correct Answer
    B. Some individuals have a better chance to produce more offspring.
    Explanation
    The correct answer is "some individuals have a better chance to produce more offspring." This answer is supported by the principle of natural selection, which states that individuals with traits that are advantageous for their environment are more likely to survive and reproduce. These individuals pass on their advantageous traits to their offspring, increasing the frequency of these traits in the population over time. This process leads to the evolution of species as the traits that provide a reproductive advantage become more common in subsequent generations.

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