Question

Explain how the primary transcript of a single eukaryotic gene can produce different proteins, using Drosophila sex-specific courting behavior as an example.

Briefly describe how genomic imprinting can be inferred from inheritance patterns in human pedigrees.

Answer 1

A primary transcript is the RNA obtained by transcription of DNA, which after processing and maturation can yield RNA products - mRNAs, tRNAs, and rRNAs. A primary transcript of a single eukaryotic gene can produce different proteins as the primary transcript for a single gene may have more than one promoter regions. In Drosophila are regulated Sexual orientation and courtship behaviour are controlled by fruitless (fru), the first gene in a branch of the sex-determining regulatory gene hierarchy. The fru gene produces a complex set of transcripts through the use of four promoters and alternative splicing. Thus, the primary transcript can control production of different proteins as it has more than one promoter.

Humans inherit two working copies of a gene, one from either parent. For some genes, a copy from one parent epigenetically silenced. Thus, though both parents contribute equally to the genetic content of their offspring, genomic imprinting can lead to the exclusive expression of specific genes from only one parent. This may lead to expression of particular trait. In case of some specific genes, pedigree of gene imprinted from maternal side is expressed phenotypically. The phenotype is expressed the allele is inherited from the mother. Thus, this allele can remain masked when they are paternally inherited, and are not phenotypically expressed, however these allele are expressed phenotypically again children of carrier daughters. Thus, genomic imprinting can be inferred from inheritance patterns in human pedigrees.