2GT3 Chapter 5
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Questions and Answers

Which chromosome does not determine sex in Drosophila?

  • Autosome
  • X chromosome
  • Y chromosome (correct)
  • Z chromosome

    • In Drosophila, what is the ratio of X chromosomes to haploid sets of autosomes in normal males?

  • 1:3
  • 1:2 (correct)
  • 1:1
  • 2:1

    • Which theory states that the balance between X and autosomes determines sex differentiation in Drosophila?

  • Chromosomal Aberration Theory
  • Genomic Imprinting Theory
  • Genic Balance Theory (correct)
  • Genetic Determination Theory

    • Which environmental factor influences sex determination in reptiles like crocodiles and turtles?

    <p>Temperature</p> Signup and view all the answers

    In reptiles with temperature-dependent sex determination, what happens at low temperatures?

    <p>100% females are produced</p> Signup and view all the answers

    Which region of the Y chromosome shares homology with regions on the X chromosome and recombines with it during meiosis?

    <p>Pseudoautosomal Regions (PARs)</p> Signup and view all the answers

    What is the function of the SRY gene located adjacent to the pseudoautosomal region of the Y chromosome?

    <p>Triggers testes formation</p> Signup and view all the answers

    Which gene on the Y chromosome is responsible for male sex determination in mammals?

    <p>SRY gene</p> Signup and view all the answers

    What is the primary sex ratio reflective of in a population?

    <p>Proportion of males to females conceived</p> Signup and view all the answers

    Which region of the Y chromosome is classified as heterochromatic?

    <p>Male-specific Region of the Y (MSY)</p> Signup and view all the answers

    What is the most common characteristic found in males with 47,XYY karyotype?

    <p>Subnormal intelligence</p> Signup and view all the answers

    During early embryonic development, the embryo is initially hermaphroditic, which means:

    <p>The gonadal phenotype is sexually indifferent</p> Signup and view all the answers

    The Y chromosome in humans has approximately how many genes?

    <p>900-1400 genes</p> Signup and view all the answers

    Which chromosome is responsible for triggering the differentiation of gonadal ridges into ovaries or testes in humans?

    <p>Y chromosome</p> Signup and view all the answers

    Which gene on the Y chromosome plays a crucial role in male sexual differentiation?

    <p>SRY gene</p> Signup and view all the answers

    What is the primary role of the Y chromosome in determining maleness?

    <p>The Y chromosome contains genes that trigger the differentiation of the gonadal ridges into testes.</p> Signup and view all the answers

    What is the primary cause of Klinefelter syndrome?

    <p>Nondisjunction during meiosis, resulting in an extra X chromosome.</p> Signup and view all the answers

    What is the primary characteristic of Turner syndrome?

    <p>Female external genitalia and internal ducts but ovaries are rudimentary.</p> Signup and view all the answers

    What is the most common characteristic found in males with 47,XYY karyotype?

    <p>Tall stature</p> Signup and view all the answers

    What is the primary function of the pseudoautosomal region of the Y chromosome?

    <p>It shares homology with regions on the X chromosome and recombines with it during meiosis.</p> Signup and view all the answers

    What is the most common karyotype associated with Triplo-X syndrome?

    <p>47,XXX</p> Signup and view all the answers

    Which chromosomal phenomenon is responsible for dosage compensation between males and females?

    <p>Random X chromosome inactivation</p> Signup and view all the answers

    What is the significance of Barr bodies observed in female somatic cells?

    <p>They represent the inactivated X chromosome</p> Signup and view all the answers

    What is the key characteristic of individuals with Klinefelter syndrome (47,XXY)?

    <p>They have two active X chromosomes</p> Signup and view all the answers

    What is the primary reason why females with Turner syndrome (45,XO) are not entirely normal?

    <p>They lack an active X chromosome</p> Signup and view all the answers

    What is the primary reason why females with triple or tetra Xs (47,XXX or 48,XXXX) are not entirely normal?

    <p>They have an imbalance in X chromosome dosage</p> Signup and view all the answers

    What is the primary function of the SRY gene located on the Y chromosome?

    <p>It triggers the differentiation of gonads into testes</p> Signup and view all the answers

    What is the primary role of the pseudoautosomal regions (PARs) on the Y chromosome?

    <p>To facilitate synapsis and recombination with the X chromosome during meiosis</p> Signup and view all the answers

    What is the role of the SRY (sex-determining region) gene on the Y chromosome?

    <p>It triggers the formation of testes during embryonic development</p> Signup and view all the answers

    What is the primary cause of Klinefelter syndrome?

    <p>The presence of an extra X chromosome (47,XXY)</p> Signup and view all the answers

    What is the primary cause of Turner syndrome?

    <p>The absence of a functional Y chromosome</p> Signup and view all the answers

    What is the primary sex ratio reflective of in a population?

    <p>The proportion of males to females conceived</p> Signup and view all the answers

    What is the primary function of the male-specific region (MSY) of the Y chromosome?

    <p>To encode proteins responsible for male sexual differentiation</p> Signup and view all the answers

    What is the primary cause of the male phenotype in individuals with Klinefelter syndrome (47,XXY)?

    <p>The extra X chromosome is inactivated through a process similar to X-inactivation in females.</p> Signup and view all the answers

    What is the primary reason for the tall stature observed in individuals with 47,XYY syndrome?

    <p>The extra Y chromosome carries genes that promote increased height.</p> Signup and view all the answers

    What is the primary factor that triggers the differentiation of gonadal ridges into ovaries or testes during early embryonic development in humans?

    <p>The presence or absence of the Y chromosome.</p> Signup and view all the answers

    In individuals with 47,XXX syndrome (Triplo-X), what is the primary reason for the observed phenotypic variability?

    <p>The degree of X-inactivation and the specific genes affected vary between individuals.</p> Signup and view all the answers

    What is the primary reason for the male phenotype in individuals with a normal 46,XY karyotype?

    <p>The presence of the Y chromosome triggers male development through the SRY gene.</p> Signup and view all the answers

    What is the primary reason for the observed intellectual disability in some individuals with 47,XXX syndrome (Triplo-X)?

    <p>The degree of X-inactivation and the specific genes affected vary between individuals.</p> Signup and view all the answers

    What is the primary function of the XIST RNA in mammals?

    <p>It binds to and inactivates one of the X chromosomes</p> Signup and view all the answers

    In Drosophila, what determines sex?

    <p>The ratio of X chromosomes to autosomes</p> Signup and view all the answers

    Which of the following patterns of temperature-dependent sex determination (TSD) in reptiles is correct?

    <p>Low temperatures yield females, and high temperatures yield males</p> Signup and view all the answers

    Which human chromosomal condition is associated with the presence of an extra X chromosome in females?

    <p>47,XXX syndrome (Triplo-X)</p> Signup and view all the answers

    What is the primary role of the Y chromosome in human sex determination?

    <p>It triggers the differentiation of gonadal ridges into testes</p> Signup and view all the answers

    Which chromosomal condition in humans is associated with the presence of an extra Y chromosome?

    <p>Klinefelter syndrome (47,XXY)</p> Signup and view all the answers

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