a. In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic?
b. Who determines the sex of an unborn child? Mention whether temperature has a role in sex determination.
OR
Give an account of post transcriptional modifications of a eukaryotic mRNA with diagramatic representation
(a) • Birds are the best examples of female heterogamety.
• Females decide the sex of the off springs.
Female bird – ZW, Male bird- ZZ
(b) • Organisms with male heterogametes like humans, males are the deciding factor in the sex determination of the off spring.
• Whereas in birds, where female are heterogametic, sex is determined by the mother.
• In some of the organisms like crocodiles sex determination depends on temperature.
• In crocodiles it is observed above 320C males are formed and below it the females are produced.
OR
1. Splicing- primary transcripts contain exons and inrons.
Introns are the sequences which don’t code for any protein. Hence, they need to be removed. The intron sequences form loops and then are cleaved.
2. Capping and tailing: as in eukaryotes RNA is transported from nucleus to the cytoplasm, it needs some protection in order to avoid degradation of DNA.
Hence, at the 3’ end poly adenylate chain, and at the 5’ end methyl gaunosine triphosphate residues are added.