Question

A duplicated chromosome has how many chromatids?
A) One
B) Two
C) Three
D) Four

Answer 1

Hint: The chromatid is half of the duplicated chromosome which gets separated during the cell division. The chromatids are identical to each other and are joined by a centromere.

Complete answer: Chromosomes contain the DNA inside the cell. The cell DNA is duplicated in the preparatory phase of the cell division (interphase). In both meiosis and mitosis, there is a duplication of chromosomes at least once. The chromosomes are a very condensed form of the DNA present in the nucleus. During DNA replication the chromosome is uncoiled and the whole double-stranded DNA is duplicated forming the replication fork. The duplicated DNA separately undergoes the stages of forming a chromosome with histone proteins and supercoiled DNA. Then after the coiling, the identical chromosomes are linked together by the centromere and form a duplicated chromosome. A single part of the duplicated chromosome is known as the chromatid which is separated during the cell division and each cell gets one chromatid. Thus, the duplicated chromosome has two sister chromatids.
Hence, the correct option is option B.

Additional information: There are four types of chromosomes based on the position of their centromeres present. They are; acrocentric, metacentric, sub-metacentric and telocentric.

Note: The single chromatid is the part where a divided cell gets one chromatid each and not half of the chromatid. A tetrad is a form of two chromatids and one duplicated chromosome. The two duplicated chromosomes during the crossing over are known as bivalent.