Question

Sister chromatids of a chromosome have
A. Same alleles at different loci
B. Different genes at the same locus
C. Different alleles of the same gene at the same locus
D. Same alleles of the same gene at the same locus

Answer 1

Hint: A chromatid is one-half of a replicated chromosome. Before cell division, chromosomes are copied and joined together in centromeres. Each strand of that chromosome is chromatid.

Complete answer:
Joined chromatids are called sister chromatids. Chromatids are formed in both cellular division processes of mitosis and meiosis. It is produced from chromatin fibres. Chromatin is composed of DNA and skeletal proteins. It condenses DNA , condensed chromatin fibres form chromosomes. After replication it appears an X- chromosome.

When sister chromatids are in close proximity to one another during cell division. There is an exchange of genetic material. The sister chromatids carry the same genes in the same loci but can have different alleles. It is because of one half from the same.

The correct answer is option C because sister chromatids are duplicated copies of each other so they will possess the same alleles of the same gene at the same locus.

Hence the correct answer is option ‘C’.

Note: It is vital that chromosomes separate correctly during cell division. Any failure of homologous chromosomes or chromatids to separate correctly is known as nondisjunction. It occurs during anaphase of mitosis or either stage of meiosis.