Question

C-value paradox is
A. Diploid DNA content
B. Haploid DNA content
C. Variation of C-value
D. Constancy of C-value

Answer 1

The paradox of the C-value is related in terms of known feature to the DNA amount present. This means that very similar or equivalent C-values can display tremendous variations, such as in complex eukaryotes, where the amount of genomic DNA is much greater than the amount needed for protein encoding.

Complete answer:
The sum of DNA present is known as the C-Value in the haploid genome of an organism. This C-value varies widely with the complexity of the organism, from prokaryotes to invertebrates and vertebrates as well as plants. The paradox of the C-value is related to the excessive amount of DNA present in eukaryotic organisms and to the difference of the C-value between eukaryotic species of equal complexity.
On the basis of junk DNA in the chromosomes and the huge amount of structural DNA present, the C-value paradox is clarified. In the human genome and its haploid genome, for example, around 21,000 genes are present, around 3.3 billion base pairs are present, while around 19 to 20,000 protein-encoding genes are present in a nematode called Caenorhabditis elegans, which normally lives in the soil and its haploid genome. Some of the factors that help to understand the paradox of the C-value include repeated DNA, introns in genes, pseudogenes, intergenic sequences.
The correct choice is C, i.e., C-value variation.

Note: Between the concept of the C-value and the C-value paradox, the student may get confused. C-value means the haploid DNA content per nucleus value that remains constant and is usually calculated in picograms, whereas the C-value paradox is the amount of DNA present in the haploid genome that differs significantly between species of similar complexity.