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प्रश्न
Jacob is genetically a carrier of the disorder that affects the shape of the RBCs, as shown in the diagram below. His son James suffers from the same disorder.
- Give the biochemical reason for the disorder that changes the shape of the RBCs, as shown above.
- Draw a Punnett square to show the genotype of the mother of James.
- Name and define the type of 'point mutation' responsible for this disorder.
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उत्तर
- Red blood cells take on a sickle-like structure when oxygen tension is lowered since the deoxygenated sickle cell haemoglobin (HbS) molecules polymerize to form long fibres.
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Given Jacob is a carrier, his genotype has to be HbA HbS.
James, Jacob's child, suffers with the condition; so, his genotype is HbS HbS.
According to the provided data, James must inherit one HbS allele from each parent if he is to have sickle call anaemia (HbS HbS). Given Jacob's known carrier status (HbAHbS), he most certainly passed on the HbS gene to James. James's need for two HbS alleles requires the mother to have likewise supplied a HbS allele. The condition (HbS HbS) or a carrier (HbA HbS) can have an impact on the mother.
Case 1. When mother is a carrier (HbA HbS)
Mother
HbA HbS HbA
JacobHbA HbA
(Normal)HbA HbS
(Carrier)HbS HbA HbS
[Carrier]HbS HbS
[Sickle cell]James will suffer from a disorder.
Case 2. When mother is affected (HbS HbS)
Mother
HbS HbS HbA
JacobHbA HbS
(Carrier)HbA HbS
(Carrier)HbS HbS HbS
[Sickle cell]HbS HbS
[Sickle cell]James will suffer from a disorder.
- A monogenetic condition, sickle cell anaemia is caused by a single base-pair point mutation in the β globin gene, substituting glutamic acid for valine in the β-globin chain.
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संबंधित प्रश्न
A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child.
Identify ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in the table given below:
| S. No. | Syndrome | Cause | Characteristics of affected individuals | Sex (male/female/both) |
| 1. | Down’s | Trisomy of 21 |
‘a’ |
‘b’ |
| 2. | ‘c’ | XXY | Overall masculine development | ‘d’ |
| 3. | Turner’s | 45 with XO |
‘e’ |
‘f’ |
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Read the following and answer from given below:
According to Mendel, one gene controls the expression of one character only. The ability of a gene to have multiple phenotypic effects because it influences a number of characters are an exception. The gene has multiple phenotypic effects because its ability to control two or more characters can be seen in cotton. In cotton, a gene for the lint also influences the height of the plant, size of the ball, number of ovules, and viability of seeds.
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