UPSC Prelims 2002 · General Studies
Question 55: Science and Technology
When one gene controls two or more different characters simultaneously, the phenomenon is called
AnswerThe answer is (b).
Pleiotropy is when a single gene affects more than one character, as with the gene for sickle-cell anaemia or phenylketonuria, which produce several effects in the body. Apomixis is seed formation without fertilisation, polyploidy is having more than two sets of chromosomes, and polyteny is the presence of many chromatid strands in giant chromosomes, as in the salivary glands of Drosophila.
Why each option is right or wrong
- (a) Apomixis is seed formation without fertilisation.
- (b) Right: pleiotropy is one gene controlling several characters.
- (c) Polyploidy means more than two sets of chromosomes.
- (d) Polyteny gives thick, many-stranded polytene chromosomes, for example in Drosophila salivary glands.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.