Question

Two chromatids of metaphase chromosome represents which of the following
a. Non – homologous chromosomes joined at the centromere
b. Maternal and paternal chromosome joined at the centromere
c. Replicated chromosomes to be separated at anaphase
d. None of the above

Answer 1

Let us first see what a chromatid is and what happens to it in the metaphase stage. The chromatid is one of the two identical halves of a replicated chromosome. During the metaphase the cell’s chromosomes will align themselves in the middle of the cell and the chromosomes which have been replicated and remained joined at a central point called the centromere are called sister chromatids.

Complete answer:
- A normal cell cycle comprises interphase (G1​phase, S phase and G2​phase) and M phase.
- The DNA duplicates due to replication during the S phase of interphase. This replication of DNA will lead into the creation of two chromatids that are joined at the centromere.
- The M phase comprises prophase, metaphase, anaphase and telophase. The chromatin material coils into distinct structures called chromosomes in the prophase.
- In the metaphase stage, chromosomes are arranged at the equator. The each chromosomes comprises of two sister chromatids produced due to DNA synthesis in the S phase that joined
- A chromosome consists of two sister chromatids joined at the centromere.
- In the anaphase stage, the centromere splits and the two sister chromatids move to opposite poles.

Hence, the correct answer is option (C).

Note: 10 chromosomes (each made of two sister chromatids) are present during the metaphase. The third phase of mitosis is called the metaphase and the process that separates the duplicated genetic material carried in the nucleus of the parent cell into 2 identical daughter cells. There is also an important checkpoint in the middle of mitosis which is called the metaphase checkpoint in which the cell makes sure that it is ready to divide.