Question

The coiling of chromonema in the prophase of mitosis is
A. Plectonemic
B. Paranemic
C. Helical
D. Irregular

Answer 1

Hint: The coiling of chromonema in the process of mitosis is because it is going to divide into or replica into a number of chromosomes. The coiling may be both, paranemic where the coiling can be easily separated or plectonemic where the coiling can't be easily separated. In meiotic chromosomes, a type of coil similar to the most important coil is described. It is referred to as the somatic or standard coil.

Complete explanation:
Option A: The coiling of chromonema in the prophase of mitosis is plectonemic which means that the double strands of the DNA are coiled collectively to form the supercoils. DNA supercoiling helps in the DNA packaging inside the nucleus of the cells due to the fact the size of DNA is long and can't fit inside the cell. Supercoiling of DNA reduces the space and allows entire DNA to be packaged. Plectonemic supercoils occur in prokaryotes, as the genetic material is a small circular chromosome.
Hence, A is the correct answer.
Option B: Paranemic coiling found in meiosis and not in mitosis where the two strands are loosely coiled that helps to make them easier to separate as during cell division, the chromonemata turn out to be condensed to form chromatids.
Hence, B is incorrect.
Option C: The helical coil model in which a prophase chromatid has organized according to the original radial loop model and then it is helically folded to form the final metaphase chromosome. So, it is not used for coiling of chromonema in the prophase of mitosis.
Hence, C is incorrect.
Option D: During the interphase, the chromatin fibril is loosely and irregularly folded. And then with the onset of mitosis it becomes more densely but is still irregularly packed to form the long prophase chromosome. And so, it is not coiled in the prophase of mitosis.
Hence, D is incorrect.

Hence, Option A. is the correct answer.

Note:
Chromosomes have to be significantly shorter than this distance, or they would prolong into the center of the dividing cell and be reduced during cytokinesis. Coiling of the chromatin fiber would create higher-order domains that ought to fold into steadily larger structures, maybe based on protein-protein. And protein-DNA interactions between neighboring chromatin fibers.