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प्रश्न
Attempt any TWO of the following:
‘The gene for sickle cell anaemia in homozygous condition is lethal and produces sickle cell trait in heterozygous carrier’. Explain.
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उत्तर
Sickle cell trait describes a condition in which a person has one abnormal allellof the hemoglobin beta gene (is hetrozygous), but does not display the severe symptoms of sickle cell disese that occur in a person who has two copies of that allele (is hemozygous). Those who are heterozygous for the sickle cell allele produce both normal and abnormal hemoglobin (the two alleles are condominant with respect to the actual concentration of hemoglobin in the circulating cells).
Sickle cell disease is a blood disorder wherein there is a single amino acid substitution in the hemoglobin protein of the red blood cells which causes these cells to assume a sickle shape, especially when under low oxygen tension. Sickling and sickle cell disease also confer some resistance to malaria parasitization of red blood cells, so that individuals with sickle-cell trait (heterozygotes) have a selective advantage in environments where malaria is present.
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संबंधित प्रश्न
Why are thalassemia and haemophilia categorized as Mendelian disorders? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.
Give an example of a human disorder that is caused due to a single gene mutation.
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’ |
During a medical investigation, an infant was found to possess an extra chromosome 21. Describe the symptoms the child is likely to develop later in the life.
A person with 47 chromosomes due to an additional Y-chromosome suffers from a condition called ______.
If both parents are carriers for thalassaemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?
This abnormality occurs due to monosomy (2n - 1); the individual has 2n = 45 chromosomes with 44 + XO genotype.
Rajesh and Mahesh have defective haemoglobin due to genetic disorders. Rajesh has too few globin molecules while Mahesh has incorrectly functioning globin molecules. Identify the disorder they are suffering from.
| Rajesh | Mahesh | |
| A. | Sickle cell anaemia - an autosome linked recessive trait | Thalassemia - an autosome linked dominant trait |
| B. | Thalassemia - an autosome linked recessive blood disorder | Sickle cell anaemia - an autosome linked recessive trait |
| C. | Sickle cell anemia - an autosome linked recessive trait | Thalassemia - an autosome linked recessive blood disorder |
| D. | Thalassemia - an autosome linked recessive blood disorder | Sickle cell anaemia - an autosome linked dominant trait |
Clotting of blood is to ______.
Give the genotype of Klinefelter’s syndrome.
