Question

Explain the connection DNA replication, mitosis, meiosis and heritable mutations.

Answer 1

Ans) We will understand the connection between the given terms in a very simplified and conceptual manner.

We know that, 1 cell divides and give rise to 2 cells by simple cell division. Now, let us elaborate the entire process.

There are 4 phases of cell cycle G1,S,G2,M. There is also resting phase i.e Go phase during which the cell will not divide or will not progress into the cell cycle. Considering the dividing cell which enters G1 phase followed by S phase also known as synthesis phase during which DNA replication occurs because Pre-RC complex (pre-replicative complex) and origin of replication are activated only after the cell enters S phase. After DNA replication, cell enters G2 phase during which the DNA replication errors are checked in case if present. Then, the cell enters M phase (mitotic phase) and at the end of M phase, 2 daughter cells (diploid) are produced from 1 parent cell (diploid). The main difference between mitosis and meiosis is that, mitosis occurs in somatic cells wheras meiosis occurs in germ cells. Main function of mitosis is to replace worn out or damaged cells wheras main function of meiosis is the formation of gametes. In meiosis, in prophase-I stage of Meiosis-I, crossing over occurs and in the Metaphase-I stage of Meiosis-I, independent reassortment occurs and these two processes introduce variations and also responsible for different combinations of gametes and this is the reason why the daughter cells are not identical to their parents after meiosis unlike in mitosis. The gametes produced will fuse in the process of fertilization and any change which occurs in the germ cells is heritable or passed on to next generation.So, if mutation occurs in the germ cells,this will be passed on too in the next generation. But, if the mutation occurs in the somatic cells, it won't be passed on to the next generation. This is the reason why DNA replication process occurs very accurately so that there will be very less chance of unrepaired mutations in the somatic as well as germ cells.