Question

Multiple alleles are present

• A. On sister chromatids
• B. At the same locus of the chromosome
• C. At different loci of the same chromosome
• D. On different chromosomes

Answer 1

The correct option is B

At the same locus of the chromosome

The correct option is option B.

Explanation for the correct option:

1. In diploid organisms, chromosomes are found in pairs.
2. The two chromosomes of each pair are called homologous chromosomes.
3. As we know that characters are controlled by genes.
4. For a particular trait, a particular gene is responsible.
5. Genes are located on chromosomes.
6. Two or more forms are possible for the same gene. These come alternatively and are called alleles.
7. So, alleles are the alternative form of a gene. If more than two forms are available for a gene, these are called multiple alleles.
8. Alleles are located on the same locus of homologous chromosomes.

Explanation of the incorrect options:

Option A:

1. Sister chromatids are copies of the same chromosome.
2. When DNA replicates two sister chromatids are formed.
3. Multiple alleles are not present on these.

Option C:

At the different loci different genes are found.

Option D:

1. On the different chromosomes multiple alleles cannot be found because like chromosomes alleles are also found in pairs.
2. Alleles are found on homologous chromosomes.

Final answer: Multiple alleles are present at the same locus of a chromosome.