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Question
Explain the inheritance of sex-linked characters in human being.
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Solution
Haemophilia is commonly known as bleeder’s disease, which is more common in men than women. This hereditary disease was first reported by John Cotto in 1803. Haemophilia is caused by a recessive X-linked gene. A person with a recessive gene for haemophilia lacks a normal clotting substance (thromboplastin) in blood, hence minor injuries cause continuous bleeding, leading to death. The females are carriers of the disease and would transmit the disease to 50% of their sons even if the male parent is normal. Haemophilia follows the characteristic criss - cross pattern of inheritaitce.
RELATED QUESTIONS
Match the terms in column I with their explanations in column II.
| Column I (Term) | Column I (Explanation) | ||
| a | genetics | 1 | Chromosomes similar in size and shape |
| b | Autosomes | 2 | The alternative forms of a gene |
| c | Recessive gene | 3 | Study of laws of inheritance of characters |
| d | Allele | 4 | A gene that can express only when in a similar pair |
| e | Homologous chromosomes | 5 | Chromosomes other than the pair of sex chromosomes |
Give Reason:
Hemophilia shows criss-cross inheritance.
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
Haemophilia exhibits X linked inheritance.
Long answer type question.
In the answer for inheritance of X-linked genes, Madhav had shown carrier male. His answer was marked incorrect. Madhav was wondering why his marks were cut. Explain the reason.
What is cris-cross inheritance?
Why are sex linked recessive characters more common in the male human beings?
Identify the CORRECT statement from the following.
Study the following statements and select the correct option.
Statement I: Holandric genes are present on Y chromosome. Statement II: Holandric genes are always inherited from father to son.
A normal man marries a female carrier for sickle cell anemia. What are the chances of having carrier children?
