C value paradox

Total amount of DNA is present in genome, it is expresed in base pair

1. C-Value Paradox Dr. R.S. Jadhav Department of Microbiology VNBN College, Shirala (MS)

2. Definition: The C-Value Paradox Total amount of DNA is present in genome, it is expressed in base pair. OR Quantity of DNA in an organism per cell, in all cells, is always constant, for a given species.  The list of organisms on this planet, with teaming millions, each have its own genome whose size varies from one species to the other and no two species have the same amount of genome nor the same genomic value or character? Variation in genomic content (both qualitatively and quantitatively) within a phylum or an order or genus is surprisingly large from   10 ×5 bp to 10 ×12 bps. Animals show variations range more than 3,300-fold, and in land plants among them differ by a factor of about 1,000.   Protists  genomes have been surprisingly vary more than 300,000-fold in size. 

3. Origin of the term the term C “ What is C Value - is it the  C ontent,  C omplement, C oncentration or what?,  if it is content then what content,  2n or n. Many authors have assumed that the "C" in "C-value" refers to "characteristic", "content", or "complement". Swift's study of this topic related specifically to variation (or lack thereof) among  chromosome  sets in different cell types within individuals, but his notation evolved into "C-value" in reference to the haploid DNA content of individual species and retains this usage today”.

4. C Value:  The amount DNA found in haploid genome, measured in million base pairs or in pg; the C may mean constancy of the genome in the species. G Value:  The number of genes found in the haploid genome; the number includes predicted and known ORFs. I value:   The amount of information embedded in the genome; their estimates effective number of genes which encompasses alternative splicing, post translational modifications, multi-domain proteins and gene redundancy plus gene expression and gene interaction.

5. Example in C value Mycoplasma              10^5 bp (-) Bacteria                 4.2 to 5x10^6 bp (+) Bacteria                2 to 8x10^6 bp Algae                          5 to 8x10^7 bp Worms                       7x10^7 to 2x10^8 bp Insects                     1.5x10^8 to 6x10^9 bp Mammals                  3x10^9 to 5x10^9 bp It is clear from above values “ as complexity increases the C-value increases from simplex to complex forms”

6. “There linear relationship between genome size and organism complexity”

7. The complexity related to C-value, i.e. there is not linear relationship between genome size and organism complexity Eg . Housefly -8.6×10×8 Both are in same group Drosophila 1.4 ×10×8 Eg . Plethodon richmondi has genome size more than Plethodon larsilli .

8. Application Due to presence of highly repetitive DNA i.e. the sequence which repeat in the genome many times

9. Thanking You