GATE 2022 BT Q.27: solution and answer

GATE 2022 · BTQ.27 · 1 mark · NAT

Assuming independent assortment and no recombination, the number of different combinations of maternal and paternal chromosomes in gametes of an organism with a diploid number of 12 is ________.

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Answer and solution

ANSWER

The number of different combinations of maternal and paternal chromosomes in the gametes is 64.

Official answer: 64Source: Official answer key, GATE 2022 BT (IIT Kharagpur)

Diploid number 2n = 12, so the haploid number of chromosome pairs is n = 12 / 2 = 6.
Independent assortment means each of the 6 homologous pairs segregates independently during meiosis: for each pair, a gamete gets either the maternal or the paternal chromosome, giving 2 independent choices per pair.
With 6 independent pairs, the total number of distinct maternal/paternal combinations in a gamete is $2^{6}$ .
$2^{6} = 64$ .

KEY IDEA

With independent assortment, each homologous chromosome pair segregates independently, so a gamete can receive the maternal or paternal member of each pair; the number of distinct combinations is $2^{n}$ , where $n$ is the haploid chromosome number.

WATCH OUT FOR

Using the diploid number (12) directly as the exponent instead of first halving it to get the haploid number of pairs (6), which gives a wrong answer of $2^{12}$ .

From the GATE 2022 BT paper. Every question of this paper · Download the full paper · All 10 Mendelian genetics questions, with notes

GATE 2022 BT Q.27: solution and answer

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