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Practice each question, then open the answer or worked solution.
All genes located on the same chromosome: ?
Ans: (b)
Morgan showed that genes located on the same chromosome formed one linkage group; however, linkage or no linkage depends on the proximity of the two genes. Genes which are closer show more likelihood of linkage hence the correct option is (b).
Conditions of a karyotype 2n ± 1 and 2n ± 2 are called:
Ans: (a)
Failure of segregation of chromatids during cell division cycle results in gain or loss of chromosome. This condition is called aneuploidy so the correct answer is (a).
Distance between the genes and percentage of recombination shows:
Ans: (b)
Chances of recombination decreases with increased distance between genes. Hence there is an inverse relationship between the two and the correct option is (b).
If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is:
Ans: (d)
Here, the defective gene is present on the X-chromosome but the disease is manifested in men and women are carriers. So, the answer is (d).
In sickle cell anaemia glutamic acid is replaced by valine. Which one of the following
triplets codes for valine?
Ans: (d)
The substitution of amino acid in the globin protein results due to the single base substitution at sixth codon of beta globin gene from GAG to GUG which codes for valine.
Person having genotype IA IB would show the blood group as AB. This is because of:
Ans: (b)
When F1 generation resembles both parents, it is co-dominance which is mostly seen in ABO blood grouping. As both A and B sugars are dominant, it results in AB blood group therefore the answer is (b).
ZZ / ZW type of sex determination is seen in:
Ans: (d)
This type of sex determination is seen in birds. The female has a ZW combination while the male has ZZ combination so the answer is (d).
A cross between two tall plants resulted in offspring having few dwarf plants. What
would be the genotypes of both the parents?
Ans: (b)
In case of TT and Tt; all offspring would be tall (TT, Tt). In case of option ‘c’ no gene for dwarf is present, so all offspring will be tall. In option ‘d’ one of the parent plant is dwarf, so it is incorrect. In option ‘b’ most of the offspring will be tall and a few will be dwarf (TT, Tt, tt). So, ‘b’ is the correct answer.
In a dihybrid cross, if you get 9:3:3:1 ratio it denotes that:
Ans: (b)
The alleles of two genes are segregating independently. This shows the perfect dihybrid ratio according to Mendel. Hence, the alleles of two genes are segregating independently and therefore the answer is (b).
Which of the following will not result in variations among siblings?
Ans: (b)
Linkage happens in all cases whenever two genes are located on the same chromosome and are close to each other. Thus, linkage has nothing to do with variation therefore the answer is (b).