Please explain this in detail including concept of this type of Mendelian inheri
ID: 186910 • Letter: P
Question
Please explain this in detail including concept of this type of Mendelian inheritance. Thanks! ,.43 .13 In Drosophila, the mutant allele bwdts causing brown eyes (normal eyes are red) is temperature sensitive. In flies reared at 29 °C the mutant allele is dominant, but in flies reared at 22oC the mutant allele is recessive. In a cross of bwdts/+ × bwdty+ where the + sign denotes the wild-type allele of bwdts, what is the expected ratio of brown-eyed flies to red-eyed flies if the progeny are reared at 29°C? At 22°C?Explanation / Answer
According to the information, the inheritance of eye color in the flies is dependent upon the ambient temperature. The eye color is brown under higher temperature due to dominant behaviour of the allele, whereas the eye color is red under lower temperature due to recessive behaviour of the same allele. This phenomenon can be described in the form of differntial activation of the sigma factors or promoters in the genes.
This is very well known fact that expression of a gene requires binding of RNA polymerase to the promoter region of the gene which in turn requires binding of appropriate sigma factor to it. Studies have shown that stress/stimulus dependent activation of different types of sigma factors is capable of altering the nature of gene expression in the organisms thus altering its phenotype. Here, it is highly likely that there are two types of sigma factors which bind to the promoter region of the gene responsible for eye color and thus alter the phenotype. The sigma factor at higher temperature is different from the one that binds at lower temperature.
Hence, it is very clear from the discussion above that the eye color of the flies is dependent upon the temperature, and consequently upon the nature of gene expression.
Thus, the flies would have dominant phenotype and brown eyes at 29 degree celcius.
The flies would bear recessive phenotype and red eyes at 22 degree celcius.