Sex Determination and X-Linked Genes Quiz
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Questions and Answers

What is the physical basis of Mendelian inheritance?

  • Genes are located on chromosomes. (correct)
  • Genes are located only in the cytoplasm.
  • Genes are located in the nucleus but not on chromosomes.
  • Genes are not related to chromosomes.

    • In diploid cells, how are chromosomes and genes present?

  • In random combinations
  • In pairs (correct)
  • Individually
  • In triplets

    • What tends to happen to linked genes during inheritance?

  • They tend to separate during inheritance due to their proximity on the same chromosome.
  • They tend to be inherited together because they are located near each other on the same chromosome. (correct)
  • They exhibit independent assortment during inheritance.
  • They tend to recombine during inheritance regardless of their proximity.

    • What causes some genetic disorders according to the text?

    <p>Alterations of chromosome number or structure</p> Signup and view all the answers

    During meiosis I, what separates?

    <p>Homologous chromosomes</p> Signup and view all the answers

    What did Thomas Hunt Morgan use to trace a gene for eye color to a specific chromosome?

    <p>Mutant male with white eyes</p> Signup and view all the answers

    What did Morgan's experiments with Drosophila provide evidence for?

    <p>Chromosomes as the location of Mendel’s heritable factors</p> Signup and view all the answers

    What is the wild type phenotype in Drosophila?

    <p>Red eyes</p> Signup and view all the answers

    In Drosophila, what is the symbol for the allele for red eyes?

    <p>w+</p> Signup and view all the answers

    What did Morgan's mating of a white-eyed male fly with a red-eyed female suggest about eye color inheritance?

    <p>The wild-type allele is dominant</p> Signup and view all the answers

    How are human genes usually written?

    <p>In all capitals</p> Signup and view all the answers

    What did Morgan's experiments with Drosophila correlate the behavior of alleles with?

    <p>The behavior of a chromosome pair</p> Signup and view all the answers

    What is the total number of chromosomes in fruit flies?

    <p>8</p> Signup and view all the answers

    What separates during meiosis II?

    <p>Sister chromatids</p> Signup and view all the answers

    What is the allele symbol for the gene involved in Huntington’s disease?

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

    What duplicates before cell division?

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

    What is the inheritance pattern of X-linked alleles from fathers to their offspring?

    <p>X-linked alleles are passed to all daughters but none of their sons</p> Signup and view all the answers

    In humans, what is the role of the Y chromosome in sex determination?

    <p>Presence of the Y chromosome and activation of specific genes lead to testes development</p> Signup and view all the answers

    What is the inheritance pattern of X-linked alleles from mothers to their offspring?

    <p>X-linked alleles are passed to both sons and daughters</p> Signup and view all the answers

    How do females express X-linked recessive traits?

    <p>Females express X-linked recessive traits only if they are homozygous for the allele</p> Signup and view all the answers

    How do males express X-linked recessive traits?

    <p>Males express X-linked recessive traits if they inherit the recessive allele from their mother</p> Signup and view all the answers

    Which disorder is almost always inherited as an X-linked trait?

    <p>Color blindness</p> Signup and view all the answers

    What is the approximate number of X-linked genes in the human X chromosome?

    <p>1,100</p> Signup and view all the answers

    What is the approximate number of genes in the Y chromosome?

    <p>78</p> Signup and view all the answers

    What is the main role of the gene WNT4 in humans?

    <p>Promotes ovary development</p> Signup and view all the answers

    What is the sex determination process in humans?

    <p>Involves a network of gene products and is more complex than previously thought</p> Signup and view all the answers

    What is the impact of the inheritance pattern of X-linked genes on the transmission of X-linked recessive traits?

    <p>Leads to specific transmission of X-linked recessive traits</p> Signup and view all the answers

    How can the phenotypes of children resulting from a color-blind woman marrying a man with normal color vision be predicted?

    <p>Using the inheritance pattern of X-linked recessive traits</p> Signup and view all the answers

    What did Thomas Hunt Morgan conclude about the location of the gene for the white-eye trait based on his experiments with fruit flies?

    <p>It was located exclusively on the X chromosome</p> Signup and view all the answers

    What did the F2 generation in Morgan's experiment with fruit flies show in terms of the phenotypic ratio?

    <p>3 red-eyed flies to 1 white-eyed fly, with the white-eyed trait being recessive to the wild-type red-eye trait</p> Signup and view all the answers

    What did Morgan's conclusion about the expression of the recessive white-eye trait only in males in the F2 generation suggest?

    <p>The eye color gene was located on the X chromosome</p> Signup and view all the answers

    What did Morgan's work with fruit flies provide support for?

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

    What did Morgan's experiments with fruit flies indicate about genes located on a sex chromosome?

    <p>They exhibit unique inheritance patterns</p> Signup and view all the answers

    What would be the difference in the phenotypes of the F2 flies if the eye color gene was located on an autosome instead of a sex chromosome?

    <p>The phenotypes would differ from what was observed</p> Signup and view all the answers

    What is the physical basis of Mendelian inheritance according to the text?

    <p>The separation of homologs during anaphase I and the random arrangement of chromosome pairs at metaphase I</p> Signup and view all the answers

    What did Morgan's mating of a white-eyed male fly with a red-eyed female suggest about eye color inheritance?

    <p>That the white-eye trait is recessive to the red-eye trait</p> Signup and view all the answers

    What is the symbol for the allele for red eyes in Drosophila?

    <p>w+</p> Signup and view all the answers

    What separates during meiosis I according to the text?

    <p>Homologous chromosomes</p> Signup and view all the answers

    What is the wild type phenotype in Drosophila according to the text?

    <p>Red eyes</p> Signup and view all the answers

    What is the phenotypic ratio resulting from the dihybrid cross of pea plants for seed color and seed shape?

    <p>9:3:3:1</p> Signup and view all the answers

    In Drosophila, what determines the sex of the offspring?

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

    In some species, how is sex determined?

    <p>By environmental factors such as temperature</p> Signup and view all the answers

    In birds, some fishes, and some insects, which sex chromosome present in the egg determines the sex of the offspring?

    <p>Not the sperm</p> Signup and view all the answers

    What is the sex determination system in grasshoppers and some insects?

    <p>Females are XX, males have only one sex chromosome (X0)</p> Signup and view all the answers

    What did Morgan's discovery of a trait (white eyes) correlated with the sex of flies support?

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

    What determines the sex in humans and other mammals?

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

    What is the role of the Y chromosome in mammalian sex determination?

    <p>Determines sex based on the sperm cell containing an X or Y chromosome</p> Signup and view all the answers

    What is the approximate number of chromosome pairs in pea plants?

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

    What determines the sex in Drosophila?

    <p>Ratio of the number of X chromosomes to the number of autosome sets</p> Signup and view all the answers

    What is the sex determination system in birds, some fishes, and some insects?

    <p>The sex chromosomes present in the egg (not the sperm) differ and determine the sex of the offspring</p> Signup and view all the answers

    What is the role of the Y chromosome in sex determination in humans?

    <p>Determines sex based on whether the sperm cell contains an X or Y chromosome</p> Signup and view all the answers

    Study Notes

    Understanding Sex Determination and Inheritance of X-Linked Genes

    • In the haplo-diploid system, most bee and ant species lack sex chromosomes, with females being diploid and males being haploid, developing from unfertilized eggs.
    • In humans, the development of anatomical signs of sex depends on the presence of the Y chromosome and the activation of specific genes, such as SRY, for testes development.
    • X-linked genes in humans follow a specific inheritance pattern, with fathers passing X-linked alleles to all daughters but none of their sons, while mothers can pass X-linked alleles to both sons and daughters.
    • Females express X-linked recessive traits only if they are homozygous for the allele, while males, having only one locus, are hemizygous and will express the trait if they inherit the recessive allele from their mother.
    • Despite the higher probability of males inheriting X-linked recessive disorders, females can also inherit these traits, such as color blindness, which is almost always inherited as an X-linked trait.
    • Some X-linked disorders, like Duchenne muscular dystrophy, are more serious, affecting about one in 5,000 males and leading to progressive muscle weakening and loss of coordination.
    • The human X chromosome contains approximately 1,100 X-linked genes, while the Y chromosome contains 78 genes, with about half being expressed only in the testis and required for normal testicular functioning.
    • The Y chromosome is passed along virtually intact from father to son, with very few disorders being transferred from father to son on the Y chromosome due to the limited number of Y-linked genes.
    • The development of female gonads in humans requires a gene called WNT4, which promotes ovary development, while the sex determination process involves a network of gene products and is more complex than previously thought.
    • Sex determination research is ongoing and may yield a more sophisticated understanding in the future, as variations exist, including individuals with a different number of sex chromosomes or with intersex characteristics.
    • The inheritance pattern of X-linked genes differs from that of autosomal genes, leading to specific transmission of X-linked recessive traits, as demonstrated in the example of red-green color blindness.
    • The phenotypes of children resulting from a color-blind woman marrying a man with normal color vision can be predicted using the inheritance pattern of X-linked recessive traits.

    Chromosomal Basis of Inheritance and Sex Determination

    • Pea plant genes specify seed color (Y for yellow, y for green) and seed shape (R for round, r for wrinkled)
    • These genes are on different chromosome pairs, with seven chromosome pairs in total
    • Fertilization results in the 9:3:3:1 phenotypic ratio in the F2 generation
    • Morgan's discovery of a trait (white eyes) correlated with the sex of flies supported the chromosome theory of inheritance
    • Sex chromosomes X and Y determine sex in humans and other mammals
    • The Y chromosome is much smaller than the X chromosome
    • Mammalian X-Y system determines sex based on whether the sperm cell contains an X or Y chromosome
    • In Drosophila, sex depends on the ratio of the number of X chromosomes to the number of autosome sets
    • In some species, sex is determined by environmental factors such as temperature
    • In grasshoppers and some insects, females are XX, males have only one sex chromosome (X0)
    • In birds, some fishes, and some insects, the sex chromosomes present in the egg (not the sperm) differ, and thus determine the sex of offspring
    • Sex determination is a matter of chance, with a fifty-fifty chance of a zygote being XX (female) or XY (male)

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    Description

    Test your knowledge of sex determination and the inheritance of X-linked genes with this quiz. Explore topics such as the chromosomal basis of inheritance, X-linked disorders, and the role of sex chromosomes in determining sex in different species. Whether you're studying biology or simply curious about genetics, this quiz will challenge and expand your understanding of these fascinating concepts.

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