Biology: Sex Ratios and Population Statistics
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Questions and Answers

What is the primary sex ratio?

  • The proportion of each sex born
  • The ratio of males to females in the population
  • The actual proportion of male to female offspring
  • The proportion of males to females conceived in the population (correct)
  • What is the assumed basis for the theoretical sex ratio of 1:1?

  • Segregation of X and Y chromosomes during meiosis
  • Equal viability and motility of X- and Y-bearing sperm
  • Equal receptivity of the egg surface to X- and Y-bearing sperm
  • All of the above (correct)
  • What is the purpose of dosage compensation in humans and other mammals?

  • To maintain a 1:1 sex ratio
  • To balance the dose of X chromosome gene expression between males and females
  • To prevent excessive expression of X-linked genes
  • Both a and b (correct)
  • Based on the 1969 worldwide census data, which population had the highest secondary sex ratio?

    <p>Korean population</p> Signup and view all the answers

    What does a secondary sex ratio of 1.06 for the Caucasian population in the United States indicate?

    <p>There were more males than females born</p> Signup and view all the answers

    What is the difference between primary and secondary sex ratio?

    <p>Primary sex ratio reflects the proportion of males to females conceived, while secondary sex ratio reflects the proportion of each sex born</p> Signup and view all the answers

    What determines the sex of an individual in Drosophila?

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

    What is the normal ratio of X chromosomes to haploid sets of autosomes in female Drosophila?

    <p>2X:2A</p> Signup and view all the answers

    What happens when the ratio of X chromosomes to haploid sets of autosomes exceeds unity in Drosophila?

    <p>An inviable female (metafemale) is produced</p> Signup and view all the answers

    How does Drosophila achieve dosage compensation for X-linked genes in females?

    <p>Increased transcription rate of X-linked genes in males</p> Signup and view all the answers

    What is the role of the Sxl (Sex-lethal) gene in Drosophila?

    <p>It induces female differentiation during sex determination</p> Signup and view all the answers

    Which of the following statements about Caenorhabditis elegans is true?

    <p>Hermaphrodites have both testes and ovaries, while males have only testes</p> Signup and view all the answers

    What is the primary reason for the deviation of the sex ratio from 1.0 in humans?

    <p>Differential survival rates of male and female embryos</p> Signup and view all the answers

    Which of the following statements about dosage compensation is correct?

    <p>It ensures equal expression of X-linked genes in males and females</p> Signup and view all the answers

    What is the primary determinant of sex in humans?

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

    Which of the following statements about sex chromosomes is correct?

    <p>The X and Y chromosomes are heteromorphic (dissimilar)</p> Signup and view all the answers

    Which of the following factors can influence the secondary sex ratio (at birth) in humans?

    <p>All of the above</p> Signup and view all the answers

    In which group of organisms is sex determination primarily influenced by temperature variation?

    <p>Many reptiles</p> Signup and view all the answers

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