Question

Independent assortment of genes does not take place when:

• A. Genes are linked and located on the same chromosome
• B. Genes are located on homologous chromosomes.
• C. Genes are located on non-homologous chromosomes
• D. All of these

Answer 1

The correct option is A

Genes are linked and located on the same chromosome

The correct option is A.

Explanation of the correct option:

1. Independent assortment occurs spontaneously when alleles of at least two genes are assorted independently into gametes.
2. Consequently, the allele inherited by one gamete does not affect the allele inherited by other gametes.
3. Recombination scrambles pieces of maternal and paternal genes, which ensures that genes assort independently from one another.
4. Therefore, genes that are located on the same chromosome are not free to participate in independent assortment and are referred to as linked genes.
5. These genes tend to be inherited together as a unit.
6. They cannot participate in independent assortment as they are so tightly linked and show very low recombination.
7. For instance, because they are found together on the same chromosome, the gamete that carries the chromosome with the dominant A allele will also have the dominant B allele.

Explanation of the incorrect options:

Option B:

1. When cells divide during meiosis, homologous chromosomes are randomly distributed to daughter cells, and different chromosomes segregate independently of each other.
2. Assortment, or separation of genes, is random in pairs of homologous chromosomes.

Option C:

1. Genes that are present on separate, non-homologous chromosomes always sort independently.
2. The principle of independent assortment states that non-homologous chromosomes are sorted independently of one another during meiosis.

Option D:

1. Independent assortment only occurs when genes are located on homologous or non-homologous chromosomes.
2. It will not occur when genes are linked and located on the same chromosome.

Final answer: Independent assortment of genes does not take place when genes are linked and located on the same chromosome.