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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 |
Why do men suffer from hemophilia and colour blindness? Under what conditions do women suffer from these disorders?
Mention, if the following statement is True or False. If false rewrite the wrong statement in its correct form:
Colour blindness is a Y-linked character.
Short Answer Question.
Observe the given pedigree chart and answer the following question.
Identify whether the trait is sex-linked or autosomal.
Father of a child is colourblind and mother is carrier for colourblindness, the probability of the child being colourblind is ____________.
Which type of progeny would be produced if a normal visioned man marries a colour-blind woman?
Inheritance of hypertrichosis occurs directly from ____________.
Given diagram is a simplified representation of human sex chromosome. The gene A and B could be of ______.
Rakesh is colour blind, married to Sangeeta who is having normal v1s10n (Homozygous). They have a son and a daughter. Determine the type of vision in their children with the help of a suitable chart.
Types of sex- linked genes:
(Haemophilia, Ichthyosis, nephritis, Myopia, Hypertrichosis, Retinitis pigmentosa)
| Column 'A' | Column 'B' | |
| (1) | Completely X- linked genes | ______ |
| (2) | Completely Y- linked | ______ |
| (3) | Incompletely sex-linked genes | ______ |
