Question

Crossing over occurs between
A. Sister chromatids
B. non-sister chromatids
C. Centromeres
D. None of the above

Answer 1

Hint: Chromosomes are the thread-like structures that carry the genetic information of an organism. It is located within the nucleus of the cells. The chromosomes are composed of proteins and consist of the genetic material, which is the DNA or the deoxyribonucleic acid.

Complete answer:
Crossing over is also known as Recombination. And this occurs during Meiosis. The process involves the exchange of segments between non-sister chromatids, in homologous chromosomes. This can result in new gene combinations and brings about new characteristics. It is one of the main processes that contribute to genetic diversity.

Considering the other given options:
A.Sister chromatids are a set of chromatids that are identical and are formed during the process of replication. Therefore crossing over or recombination does not occur between sister chromatids. Hence it is not the right option.
C. Centromere is the portion on a chromosome that connects the sister chromatids. Hence it is not the right option, as recombination does not occur in the centromere.
D. None of the above is not the right option, as there is a right option among the above-given options.
Therefore from the above-given options, the most appropriate answer is B. That is, Crossing over occurs between Non- sister chromatids.

Note: The process of crossing over takes place during the Pachytene stage of Prophase I of Meiosis II. The formation of chiasmata is the distinguishing feature of this process. It is an X- shaped structure.