Question

Assertion (A) : In dihybrid crosses involving sex-linked genes in \(\textit{Drosophila}\), \(F_2\) generation of non-parental gene combinations are observed. 
Reason (R) : Two genes present on different chromosomes show linkage and recombination in \(\textit{Drosophila.}\)

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Remember that linkage applies to genes on the same chromosome, while independent assortment applies to genes on different chromosomes. Recombination can occur between linked genes due to crossing over.

Answer 1

The Correct Option is C

Assertion (A) states that in dihybrid crosses involving sex-linked genes in\( \textit{Drosophila}\), the \(F_2\) generation shows non-parental gene combinations. This is true. Sex-linked genes are located on the X chromosome. During meiosis in the \(F_1\) generation (which are heterozygous for these genes), recombination (crossing over) can occur between the sex chromosomes, leading to the formation of gametes with non-parental combinations of the linked genes. These non-parental combinations will be observed in the \(F_2\) generation. 
Reason (R) states that two genes present on different chromosomes show linkage and recombination in\( \textit{Drosophila}\). This is false. Genes located on different chromosomes assort independently according to Mendel's law of independent assortment. Linkage occurs when genes are located on the same chromosome and tend to be inherited together. Recombination occurs due to crossing over between homologous chromosomes during meiosis, which can separate linked genes, but it doesn't apply to genes on different chromosomes in the context of linkage. Genes on different chromosomes exhibit independent assortment, resulting in non-parental combinations due to the random segregation of chromosomes. Therefore, Assertion (A) is true, but Reason (R) is false.