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Biology · 2024 · 3 marks
CBSE 2024 · Region 2 · Set 2 · Q25
Explain the mechanism of haplo-diploid pattern of sex determination with the help of a suitable example. Why is this pattern so called? OR T.S.…
Explain the mechanism of haplo-diploid pattern of sex determination with the help of a suitable example. Why is this pattern so called ?
OR T.S. Morgan and his colleagues worked with Drosophila melanogaster for their experiments. State the findings they arrived at and explain how.
Marking-scheme solution
Honey bee shows mechanism of haplo-diploid pattern of sex-determination, female (queen or worker) develops from fertilized egg, so are diploid, males
(drones) develop from unfertilized egg by parthenogenesis, so are haploid,
Females are diploid having $\displaystyle 32$ chromosomes and the males are haploid having
$\displaystyle 16$ chromosomes this is haplo-diploid sex determination
In a dihybrid cross the F2 phenotypic ration deviated very significantly from
$\displaystyle 9$:$\displaystyle 3$:$\displaystyle 3$:$\displaystyle 1$, the proportion of the parental gene combination was much higher than the non-parental type, the parental combinations were due to linkage of genes
(physical association) and the non-parental types were due to distant genes
(recombination/ crossing over)
(Explanation of the same if provided through cross should be considered)
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