Valine by Glutamic acid at the 6th position of the beta globin chain
Glutamic acid by Valine at the 6th position of the beta globin chain
Valine by Glutamic acid at the 6th position of the alpha globin chain
Glutamic acid by Valine at the 6th position of the alpha globin chain
Correct Option: B [ Glutamic acid by Valine at the 6th position of the beta globin chain ]
Remark: The defect is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule.
The single base substitution at the sixth codon of the beta globin gene that causes sickle-cell anaemia is:
Remark: The substitution of the amino acid in the globin protein results from a single base substitution at the sixth codon of the beta globin gene, changing it from GAG to GUG.
Phenylketonuria is an inborn error of metabolism inherited as an autosomal recessive trait. It is caused by the lack of an enzyme that converts:
Remark: In phenylketonuria, the affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine, leading to its accumulation and conversion into phenylpyruvic acid.
Thalassemia is different from sickle-cell anaemia because it is a:
Qualitative problem of synthesising an incorrectly functioning globin
Quantitative problem of synthesising too few globin molecules
Problem related to blood clotting factors
Disorder caused by a viral infection
Correct Option: B [ Quantitative problem of synthesising too few globin molecules ]
Remark: Thalassemia differs from sickle-cell anaemia in that the former is a quantitative problem of synthesising too few globin molecules, while the latter is a qualitative problem of synthesising an incorrectly functioning globin.
Failure of segregation of chromatids during the cell division cycle, resulting in the gain or loss of a chromosome, is called:
Remark: Failure of segregation of chromatids during the cell division cycle results in the gain or loss of a chromosome(s), a condition called aneuploidy.
Down’s syndrome is caused by the presence of an additional copy of which chromosome?
Remark: The cause of Down’s syndrome is the presence of an additional copy of chromosome number 21 (trisomy of 21). The disorder was first described by Langdon Down in 1866.
Klinefelter’s syndrome is a genetic disorder caused by:
Remark: The appearance of the recessive dwarf phenotype (tt) in the offspring indicates that both parents must have carried the recessive allele (t). Since the parents were tall (dominant phenotype), they must both be heterozygous (Tt). A Tt x Tt cross yields a genotypic ratio of 1:2:1 and a phenotypic ratio of 3:1.
If a colour-blind man marries a woman who is a carrier for colour blindness, what is the probability that their son will be colour-blind?
Remark: The son of a woman who carries the gene has a 50 per cent chance of being colour blind. The man's genotype is XcY and the woman's is XhX. A son receives Y from the father and either Xh or X from the mother, giving a 50% chance of being XhY (colour-blind).
