BIO207H5S Introductory Genetics Winter 2024 Lecture 5: Sex Determination and Sex-linked Inheritance
38 Questions
3 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

In the XX-XY sex determination system, which of the following statements is true?

  • Males produce only X gametes.
  • Females produce both X and Y gametes.
  • All somatic cells in human females contain one X and one Y chromosome.
  • Males inherit their X chromosome from their father and their Y chromosome from their mother. (correct)

    • How many genes are there on the Y chromosome compared to the X chromosome in humans?

  • Equal number of genes on both X and Y chromosomes
  • 900–1400 genes on the Y chromosome and ~75 genes on the X chromosome (correct)
  • Y chromosome has more genes than the X chromosome
  • Both X and Y chromosomes have around 1000 genes

    • What determines maleness in the XX-XY sex determination system?

  • Sperm cells that carry the X chromosome
  • Females producing only X gametes
  • Presence of two X chromosomes
  • Sperm cells that carry the Y chromosome (correct)

    • During early development, every human embryo is potentially hermaphroditic until around which week of gestation?

    <p>Fifth week</p> Signup and view all the answers

    At what stage does the gonadal tissue of a human embryo become sexually indifferent or neutral?

    <p>Fifth week of gestation</p> Signup and view all the answers

    Which part of the neutral gonadal tissue may develop into a testis in a human embryo?

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

    In humans, how many X chromosomes do males inherit from each parent?

    <p>No X chromosomes from their father and one X chromosome from their mother</p> Signup and view all the answers

    Which type of sex cells do females produce in the XX-XY sex determination system?

    <p><strong>X</strong> gametes</p> Signup and view all the answers

    What can be distinguished at the stage where the gonadal phenotype is sexually indifferent?

    <p>Neither male nor female reproductive structures</p> Signup and view all the answers

    What determines maleness in humans according to the XX-XY sex determination system?

    <p>Sperm cells that carry the Y chromosome</p> Signup and view all the answers

    In the XX-XO system, which of the following accurately describes the determination of maleness?

    <p>Males carry only one X chromosome (XO)</p> Signup and view all the answers

    What is the role of the Wolffian ducts and Müllerian ducts in each embryo?

    <p>Differentiate into structures of the male reproductive tract</p> Signup and view all the answers

    What is the function of the testis determining factor?

    <p>Cause undifferentiated gonadal tissue to form testes</p> Signup and view all the answers

    What are the pseudoautosomal regions (PARs) critical for?

    <p>Segregation of the X and Y chromosomes during male gametogenesis</p> Signup and view all the answers

    What genetic consequences result from having more than two copies of pseudoautosomal regions (PARs)?

    <p>Klinefelter’s Syndrome (XXY)</p> Signup and view all the answers

    What is the function of Barr bodies in somatic cells of females?

    <p>Compensate for X chromosome dosage disparities</p> Signup and view all the answers

    According to the Lyon hypothesis, when does X chromosome inactivation occur?

    <p>At the blastocyst 4- to 8-cell stage of development</p> Signup and view all the answers

    What is the basis for sex determination in organisms with Haplodiploidy?

    <p>Number of chromosomes found per cell</p> Signup and view all the answers

    What is the mechanism of sex determination in organisms with XX-XY system?

    <p>Females have XX chromosomes and males have XY chromosomes</p> Signup and view all the answers

    In Drosophila melanogaster, which one of the following accurately describes the sex-linkage pattern for the gene controlling eye color?

    <p>F1 : Red eyed female : Red eyed male : white eyed male :: 2:1:1</p> Signup and view all the answers

    What did Calvin Bridges' observation of flies with unusual phenotypes cytogenetically confirm?

    <p>Non-disjunction of chromosomes during gamete formation</p> Signup and view all the answers

    Which statement accurately represents Morgan’s Hypothesis on X-linkage in Drosophila melanogaster?

    <p>Males have only one available gene site on their single X chromosome, whereas females have two available gene sites, one on each X chromosome.</p> Signup and view all the answers

    What was the significance of conducting reciprocal crosses in the study of sex-linkage in Drosophila?

    <p>It allowed researchers to test if a gene or trait is autosomal or sex-linked.</p> Signup and view all the answers

    What did the observation of unexpected phenotypes at a frequency more than the expected mutation rate in Morgan’s crosses indicate?

    <p>Non-disjunction of chromosomes during gamete formation</p> Signup and view all the answers

    What was one result of X-linkage according to Morgan’s hypothesis?

    <p>Phenotypic traits controlled by recessive X-linked genes are passed from homozygous mothers to all sons.</p> Signup and view all the answers

    Which of the following accurately describes the F1 offspring obtained in a reciprocal cross for an autosomal gene or trait?

    <p>All offspring will show the dominant phenotype for F1 for any monohybrid cross.</p> Signup and view all the answers

    In Morgan’s studies, what did the observation of a white eyed male fly as opposed to red eyed flies lead to?

    <p>Curiosity that led to documenting one of the first cases of sex-linkage in Drosophila.</p> Signup and view all the answers

    What genetic phenomenon did Calvin Bridges' observation confirm about the flies with unusual phenotypes?

    <p>Non-disjunction of chromosomes during gamete formation.</p> Signup and view all the answers

    What did Bridges' observation confirm about the flies' rare phenotypes?

    <p>They were associated with particular chromosomes due to non-disjunction during gamete formation.</p> Signup and view all the answers

    What is the sex determination system present in butterflies, birds, some reptiles, and amphibians?

    <p>ZZ-ZW system</p> Signup and view all the answers

    According to Bridges, what plays a critical role in sex determination in Drosophila melanogaster?

    <p>X chromosomes and autosomes</p> Signup and view all the answers

    What did Thomas H. Morgan observe in his Drosophila lab cultures, leading to his studies of sex-linkage?

    <p>A white eyed male fly</p> Signup and view all the answers

    What was Morgan's hypothesis regarding the allele for white eyes in Drosophila?

    <p>It is found on the X chromosome but absent from the Y chromosome</p> Signup and view all the answers

    What is the definitive method to test for sex-linkage?

    <p>Reciprocal crosses</p> Signup and view all the answers

    In a reciprocal cross, if the gene or trait is autosomal, what will be observed in the offspring?

    <p>All of the offspring will show the dominant phenotype for F1 for any monohybrid cross</p> Signup and view all the answers

    What is observed in the offspring of a reciprocal cross if the gene or trait is sex-linked?

    <p>The offspring in F1 or F2 obtained in a reciprocal cross will be different</p> Signup and view all the answers

    What did Calvin Bridges observe under the microscope to confirm his hypothesis regarding unusual phenotypes?

    <p>Chromosomes associated with particular phenotypes</p> Signup and view all the answers

    What did unexpected phenotypes appearing at a frequency more than the expected mutation rate provide definite proof for?

    <p>Chromosomal theory of inheritance</p> Signup and view all the answers

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser