Sex-Linked Inheritance Overview
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Questions and Answers

What term is used to describe the inability to see red color due to a hereditary condition?

  • Tritanopia
  • Deuteronopia
  • Achromatopsia
  • Protonopia (correct)

    • What is the genetic status of a male with color blindness?

  • Diploid
  • Homozygous
  • Hemizygous (correct)
  • Haploid

    • How is color blindness inherited in families?

  • From mother to son
  • From father to grandson through daughter (correct)
  • From mother to daughter only
  • From father to daughter

    • Which of the following statements is true regarding carriers of color blindness?

    <p>Carriers possess a dominant gene and a recessive gene.</p> Signup and view all the answers

    What represents the genetic expression of color blindness?

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

    What term is used to describe the inheritance of traits that are controlled by genes located on the sex chromosomes?

    <p>Sex-linked inheritance</p> Signup and view all the answers

    What type of inheritance is characterized by traits that appear in alternate generations due to the passage of these traits through daughters?

    <p>Criss-cross inheritance</p> Signup and view all the answers

    Which of the following diseases is an example of an X-linked trait?

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

    Which chromosome is primarily associated with the inheritance of X-linked characters?

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

    What is the fundamental reason why sex-linked traits are more common in men than in women?

    <p>The presence of only one X chromosome in men</p> Signup and view all the answers

    Which of the following is NOT a characteristic of sex-linked inheritance?

    <p>Often present in every generation</p> Signup and view all the answers

    Which gene inheritance pattern would include diseases like Retinitis pigmentosa?

    <p>XY-linked inheritance</p> Signup and view all the answers

    What is a common misconception about Y-linked genes?

    <p>Y-linked genes can be inherited from the mother</p> Signup and view all the answers

    What is the inheritance pattern demonstrated by color blindness when a carrier daughter marries a normal man?

    <p>Some sons are color blind</p> Signup and view all the answers

    What occurs when a color blind woman marries a normal man?

    <p>All sons will be color blind</p> Signup and view all the answers

    What is a characteristic of hemophilia?

    <p>Clotting is delayed significantly</p> Signup and view all the answers

    What is the role of antihemophilic globulin in blood clotting?

    <p>It speeds up the clotting process</p> Signup and view all the answers

    What pattern of inheritance is observed in color blindness according to the provided information?

    <p>Criss-cross inheritance</p> Signup and view all the answers

    In a family where the mother is a carrier for color blindness (Cc) and the father is normal (XY), what is the probability that their son will be color blind?

    <p>50% chance</p> Signup and view all the answers

    Who discovered hemophilia and when?

    <p>John Cottington in 1803</p> Signup and view all the answers

    What type of offspring do carrier daughters produce when married to color blind men?

    <p>Equal numbers of color blind and normal offspring</p> Signup and view all the answers

    What genetic basis does haemophilia have?

    <p>Recessive gene inheritance</p> Signup and view all the answers

    Which of the following describes the inheritance pattern of haemophilia?

    <p>Criss-cross inheritance</p> Signup and view all the answers

    Why is haemophilia more common in men than in women?

    <p>Men have only one X chromosome</p> Signup and view all the answers

    What is the genetic makeup of a male who is haemophilic?

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

    If a normal woman has a carrier daughter, what is the probability of her grandchildren being haemophilic when the daughter marries a normal man?

    <p>50%</p> Signup and view all the answers

    What characteristic makes males referred to as hemizygous regarding haemophilia?

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

    What can generally happen to haemophilic patients in terms of life expectancy?

    <p>They often die before reproductive age</p> Signup and view all the answers

    In a scenario where a haemophilic man marries a normal woman, what is the genetic status of their sons?

    <p>All sons are normal</p> Signup and view all the answers

    Study Notes

    Sex-Linked Inheritance

    • The transmission of traits from parents to offspring that are linked to sex chromosomes is called sex-linked inheritance.
    • Genes located on sex chromosomes are called sex-linked genes.
    • Traits controlled by sex-linked genes are called sex-linked characters.
    • Sex-linked inheritance was discovered by T.H. Morgan in 1910.
    • Common examples of sex-linked inheritance include color blindness, hemophilia, eye color in Drosophila, hypertrichosis (hair on the ear pinna), and Ichthyosis hystrix (scales on the body).

    X-Linked Inheritance

    • Genes located on the X chromosome are called X-linked genes.
    • Inheritance of X-linked genes is called X-linked inheritance.
    • Traits controlled by X-linked genes are called X-linked characters.
    • Examples of X-linked characters include hemophilia and color blindness.

    Y-Linked Inheritance

    • Genes located on the Y chromosome are called Y-linked genes.
    • Inheritance of Y-linked genes is called Y-linked inheritance.
    • Traits controlled by Y-linked genes are called Y-linked characters.
    • Examples of Y-linked characters include hypertrichosis (hair on the ear pinna) and Ichthyosis hystrix (scales on the body).

    XY-Linked Inheritance

    • Genes located on both the X and Y chromosomes are called XY-linked genes.
    • Inheritance of XY-linked genes is called XY-linked inheritance.
    • Traits controlled by XY-linked genes are called XY-linked characters.
    • Examples of XY-linked characters include Aeroderma pigmentosum, Retinitis pigmentosa, nephritis, etc.

    Criss-Cross Inheritance

    • Sex-linked traits are often recessive and more common in males than females.
    • The inheritance of a trait from a father to his grandson through his daughter is called criss-cross inheritance (also known as Ag-ag inheritance).
    • The sex-linked character appears in alternate generations.

    Color Blindness

    • Color blindness is a sex-linked character discovered by Wilson in 1911.
    • It is a hereditary disease in which affected individuals cannot distinguish between red and green colors.
    • Protonopia is red blindness.
    • Deuteronopia is green blindness.
    • Color blindness is a recessive trait caused by recessive genes represented by cc.
    • Normal individuals possess genes CC, Cc, or C alone.
    • The recessive genes prevent the proper development of color-sensitive cells in the retina.
    • The genes for color blindness are located on the X chromosome.
    • The presence of only one gene for a character is called hemizygous.
    • Men are hemizygous for color blindness because they have only one X chromosome.
    • Color blindness is more common in men than women.
    • Color blindness follows criss-cross inheritance, being transmitted from a father to his grandson through his daughter.
    • This character is never transmitted to the son from the father.
    • A woman who carries one recessive gene for color blindness is considered a carrier.
    • Carriers are normal in their vision, but they carry the recessive gene in one of their X chromosomes.

    Haemophilia (Bleeder's Disease)

    • Haemophilia is a hereditary blood disease discovered by John Cotto in 1803.
    • It is characterized by delayed blood clotting.
    • Haemophilia is caused by the absence of a blood clotting factor called antihaemophilic globulin, which is necessary for normal blood clotting.
    • Normal blood clotting takes 2 to 8 minutes.
    • In haemophilic patients, blood clotting is delayed for 20 minutes to 24 hours.
    • Haemophilic patients bleed continuously from wounds.
    • Haemophilia is a sex-linked recessive character caused by recessive genes represented by hh and the dominant gene H.
    • Haemophilia appeared as a mutant in Queen Victoria.
    • It was transmitted to her descendants, making it common among the Royal family of Queen Victoria. This is why haemophilia is also known as Royal disease.
    • The genes for hemophilia are located on the X chromosome.
    • Men are hemizygous for hemophilia.
    • Haemophilia, like other sex-linked characters, is more common in men than women.
    • Haemophilia follows criss-cross inheritance.
    • It is transmitted from the father to his grandson through his daughter.
    • Generally, haemophilic patients die before reaching reproductive age if they are exposed to severe bleeding.
    • When a normal woman marries a haemophilic man, their sons and daughters will be normal, but the daughters are carriers containing the recessive gene for haemophilia.
    • When a carrier daughter marries a normal man, all their granddaughters are normal, but 50% of their sons are haemophilic.

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    Sex Linked Inheritance PDF

    Description

    This quiz covers the fundamentals of sex-linked inheritance, including the definitions and examples related to sex-linked, X-linked, and Y-linked genes. Discover how traits are transmitted through sex chromosomes and understand their implications in genetics. Test your knowledge on the discoveries of T.H. Morgan and specific related conditions like hemophilia and color blindness.

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