Q.38 The amount of DNA present in the genome of a species is called as
1. D-value
2. C-value
3. B-value
4. T-value
C-Value in Genome Biology: Definition and Exam Answer
The amount of DNA in a species’ haploid genome is known as the C-value, making option 2 the correct choice in this biology question.
C-Value Definition
C-value measures DNA content (in picograms) in a haploid nucleus or gamete of a eukaryotic species. It equals half the diploid somatic cell DNA and often equals genome size in diploids.
This term originated from 1950s studies noting consistent DNA amounts per species.
Option Analysis
| Option | Term | Explanation | Correct? |
|---|---|---|---|
| 1. D-value | Incorrect | No standard biology term; unrelated to DNA content. | No |
| 2. C-value | Correct | Haploid genome DNA amount (pg); e.g., human ~3.3 pg. | Yes |
| 3. B-value | Incorrect | Not used for genome size; sometimes denotes unreplicated DNA phase but not species genome. | No |
| 4. T-value | Incorrect | Unrelated; may refer to statistics or other fields, not genomics. | No |
C-Value Paradox Insight
C-value varies widely (e.g., 0.06 pg in yeast to 150 pg in some plants) without matching organism complexity, due to non-coding DNA like transposons. This “paradox” highlights junk DNA’s role.
