Question

The replication of chromosomes takes place during--
A) Interphase
B) Prophase
C) Metaphase
D) Anaphase
E) Telophase

Answer 1

The process of cell division is a very important process in all living organisms. DNA replication and cell growth can take place during the process of division in the cell. The replication of chromosomes helps in the transfer of the genetic material to the progeny.

Complete answer:
To know the answer, let us first infer the option given above:

1. Interphase – Interphase is also called the resting phase which is the time during which the cell is preparing for a division that can be done by both cell growth and DNA replication in proper order.
   The interphase is divided into the following phases, which are:
   - G1 phase: In this phase, the cell is metabolically active and continuous growth takes place without DNA replication.
   - S phase: It begins in the nucleus and marks the period during DNA replication.
   - G2 phase: Proteins are synthesized in preparation for mitosis and cell growth continues during this phase.

2. Prophase- Prophase which is the first stage of mitosis follows the S and G2 phases of interphase. The new DNA molecule that is formed in both S and G2 phases are intertwined with each other. During the process of chromatin condensation, the chromosomal material gets untangled. The centriole in which replication has taken place during the S phase of interphase will start moving towards opposite poles of the cell.

3. Metaphase-The second phase of the cycle starts with the complete disintegration nuclear in which the chromosome is mainly spread in the cytoplasm. By this stage, the condensation of chromosomes is completed and one can see these changes under the microscope. In this phase, the metaphase chromosome which is made from two sister chromosomes are held together by a centromere. At the surface of the centromere are present small discs which are called kinetochores.

4. Anaphase- Each chromosome that is arranged at the metaphase plate get split simultaneously in this phase. The two daughter chromatids that are referred to as chromosomes of the future daughter nuclei moves towards the two opposite poles. In this phase, the chromosomes move goes towards the equatorial plate after which the centromere moves towards the poles.

5. Telophase –It is the final stage of mitosis in which the chromosomes that have reached their respective poles decondense and lose them individually. One will not be able to see chromosomes after this phase and all the chromatin material will get collected in a mass in the two poles.

In the S phase, replication of chromosomes takes place which is part of the Interphase.

Therefore the correct answer is option ‘A’.

Note: Eukaryotic cell cycle divides once in approximately every 24 hours. It is discovered that the duration of the cell cycle can vary from the organism and also from cell type to cell type. Like in yeast, the cell cycle takes place after about 90 minutes only.