In the Drosophilia, the transcription of the single X- chromosome occurs at twic
ID: 208938 • Letter: I
Question
In the Drosophilia, the transcription of the single X- chromosome occurs at twice the rate of transcription whereas in the nematode, C elegans, the dosage compensation is mediated by decreased transcription in both X chromosomes of the hermaphroditic gender.
What selective adavantage do nematodes have over drosophilia when it comes to methods of dosage compensation?
What selective advantage do drosphilia have over nematodes based on considerations of hemizygosity, parental conflict, or any other criteria you think of
Explanation / Answer
The role of the Dosage compensation (DC) was hypothesised by Barbara J. Meyer in the 1980s Dosage compensation is essential in the polyploid species. For instance, in C. elegans (animal with two X-chromosome) dosage compensation is required to maintained the low transcription of genes associated with X-chromosome. However, in Drosophila sp. Which has single X-chromosome possesses very high transcription rate for the genes located on the this chromosome. The advance of DC is reduces the energy drive required during gene expression by switching them low during transcription when their expression is not required or less required. Therefore, it is common in species that male with single X-chromosome like Drosophila, human, etc., showed twice expression of genes as compared to female/hermaphrodites which has two X-chromosome. In C. elegans the number of X-chromosome determines the organism sex. For instance, worm with two X-chromosome (XX) are hermaphrodite; however, worm with single X-chromosome are male, because there is no male specific Y-chromosome is present in C. elegans. Due to DC, in an organism unnecessarily constitutive /surplus expression of X-chromosome linked genes are avoided in C. elegans. Similarly, Drosophila female with XX reduced the expression of X-linked genes by 50% as compared to male which has single X-chromosome with double expression of genes.
However, this mechanism also have drawback, because failure of expression of X-chromosome linked genes in organism could be lethal, therefore, it can also restrict the survival of C. elegans. Thus, the main benefit for hemizygous species like Drosophila overC.elegans is they escape this situation.