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Questions and Answers
What is the hereditary disease that causes an inability to distinguish between red and green colors?
What is the hereditary disease that causes an inability to distinguish between red and green colors?
What is the genetic makeup of a male who is color blind?
What is the genetic makeup of a male who is color blind?
How is the inheritance pattern of color blindness typically described?
How is the inheritance pattern of color blindness typically described?
Which term is used to describe a daughter who carries one recessive gene for color blindness but does not express the condition?
Which term is used to describe a daughter who carries one recessive gene for color blindness but does not express the condition?
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Why do sons never inherit color blindness from their fathers?
Why do sons never inherit color blindness from their fathers?
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What is the primary characteristic of genes associated with sex-linked inheritance?
What is the primary characteristic of genes associated with sex-linked inheritance?
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Which of the following examples is NOT a known sex-linked inheritance condition?
Which of the following examples is NOT a known sex-linked inheritance condition?
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What type of inheritance describes the passing of a sex-linked character from a father to his grandson through a daughter?
What type of inheritance describes the passing of a sex-linked character from a father to his grandson through a daughter?
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Which chromosome is most commonly associated with X-linked inheritance?
Which chromosome is most commonly associated with X-linked inheritance?
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What is the most common inheritance pattern for sex-linked characters?
What is the most common inheritance pattern for sex-linked characters?
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Which of the following conditions is a Y-linked inheritance characteristic?
Which of the following conditions is a Y-linked inheritance characteristic?
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What term describes genes that are located on both X and Y chromosomes?
What term describes genes that are located on both X and Y chromosomes?
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Who discovered sex-linked inheritance?
Who discovered sex-linked inheritance?
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Which statement accurately describes the inheritance of color blindness in sons?
Which statement accurately describes the inheritance of color blindness in sons?
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What is the result when a color blind woman marries a normal vision man regarding their sons?
What is the result when a color blind woman marries a normal vision man regarding their sons?
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What role does the antihaemophilic globulin play in the blood?
What role does the antihaemophilic globulin play in the blood?
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How long does it take for normal individuals to clot their blood compared to hemophiliacs?
How long does it take for normal individuals to clot their blood compared to hemophiliacs?
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What happens to daughters of a color blind father when they marry men with normal vision?
What happens to daughters of a color blind father when they marry men with normal vision?
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In criss-cross inheritance, who is primarily responsible for passing the color blindness gene to grandsons?
In criss-cross inheritance, who is primarily responsible for passing the color blindness gene to grandsons?
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What is a major characteristic of hemophilia?
What is a major characteristic of hemophilia?
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When carriers of the color blindness gene marry, what is likely to occur?
When carriers of the color blindness gene marry, what is likely to occur?
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What type of inheritance pattern does haemophilia follow?
What type of inheritance pattern does haemophilia follow?
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Why is haemophilia more common in men than in women?
Why is haemophilia more common in men than in women?
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If a normal woman marries a haemophilic man, what will be the status of their sons?
If a normal woman marries a haemophilic man, what will be the status of their sons?
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What is the probability of haemophilia in the sons of a carrier woman who marries a normal man?
What is the probability of haemophilia in the sons of a carrier woman who marries a normal man?
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What type of gene causes haemophilia?
What type of gene causes haemophilia?
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Which of the following represents the normal condition in terms of haemophilia genotype?
Which of the following represents the normal condition in terms of haemophilia genotype?
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What is the expected outcome for the granddaughters of a haemophilic man and a normal woman?
What is the expected outcome for the granddaughters of a haemophilic man and a normal woman?
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What happens to haemophilic patients who experience severe bleeding?
What happens to haemophilic patients who experience severe bleeding?
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Study Notes
Sex Linked Inheritance
- The transmission of physical traits from parents to offspring, alongside sex, is called sex-linked inheritance. This means that the genes responsible for these traits are located on the sex chromosomes (X and Y).
- Sex-linked inheritance was discovered by T.H. Morgan in 1910.
- Common examples of sex-linked inheritance include colour blindness, haemophilia, eye colour in Drosophila, hypertrichosis (hair in the ear pinna), and ichthyosis hystrix.
- Genes located on the X chromosome are called X-linked genes, and the inheritance pattern is called X-linked inheritance.
- Examples of X-linked characters include haemophilia, colour blindness, and eye colour in Drosophila.
- Genes located on the Y chromosome are called Y-linked genes, and the inheritance pattern is called Y-linked inheritance. Examples of Y-linked characters include hypertrichosis and ichthyosis hystrix.
- Genes located on both X and Y chromosomes are called XY-linked genes, with the inheritance pattern being called XY-linked inheritance. Examples include Aeroderma pigmentosum, Retinitis pigmentosa, nephritis.
Colour Blindness
- Colour blindness is a sex-linked recessive trait discovered by Wilson in 1911.
- Affected individuals cannot distinguish red and green colours.
- Red blindness is called protonopia, and green blindness is called deuteronopia.
- The recessive genes responsible for colour blindness are represented by 'cc'. Normal individuals have either CC or Cc, or just C alone (in males).
- Colour blindness genes are located on the X chromosome, with no alleles present on the Y chromosome.
- Men are hemizygous for colour blindness, meaning they only have one gene for this trait.
- Colour blindness is more common in men than women.
- Colour blindness follows criss-cross inheritance, meaning it is transmitted from father to grandson through his daughter. It only appears in alternate generations.
- Colour blindness is never transmitted directly from father to son.
- Female carriers are heterozygous for colour blindness (Cc) and have normal vision, but carry the recessive gene.
- If a normal woman (CC) marries a colour blind man (cY), all their daughters will be carriers (Cc), while their sons will inherit the normal vision gene from their mother and will be normal.
- If a carrier daughter (Cc) marries a man with normal vision, there is a 50% chance their sons will be colour blind.
- If a colour blind woman marries a normal man, all their sons will be colour blind, while their daughters will be carriers.
- If a carrier daughter marries a colour blind man, the grandchildren (both male and female) will have a 50% chance of being colour blind.
Haemophilia (Bleeder's Disease)
- Haemophilia is a hereditary blood disease discovered by John Cotto in 1803.
- It is characterized by delayed blood clotting due to the absence of an important blood clotting factor called antihaemophilic globulin.
- Normal blood clotting occurs within 2-8 minutes, while in haemophilia, it can take 20 minutes to 24 hours or more.
- Haemophilia is a sex-linked recessive trait.
- The recessive genes responsible for haemophilia are represented by 'hh', while the dominant gene is 'H'.
- Haemophilia genes are located on the X chromosome with no gene on the Y chromosome. Males are therefore hemizygous for this trait.
- Like other sex-linked traits, haemophilia is more common in men than women.
- Haemophilia follows criss-cross inheritance.
- Haemophilic patients often die before reaching reproductive age if exposed to severe bleeding.
- If a normal woman marries a haemophilic man, all their sons will be normal, but their daughters will be carriers.
- If a carrier daughter marries a normal man, their sons will have a 50% chance of being haemophilic, while their daughters will be normal or carriers.
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Description
Test your knowledge on sex-linked inheritance, a vital concept in genetics. Learn how traits are passed through sex chromosomes and explore examples like colour blindness and haemophilia. This quiz will challenge your understanding of X-linked and Y-linked inheritance patterns.
