Molecular Basis of Inheritance Test - 9

The anticodon on the t-RNA corresponding to AUG initiator codon on mRNA is UAC as A bonds with U and G bonds with C in RNA. Thymine (T) is absent in RNA.

A regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator gene (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase). In prokaryotes, regulator genes often code for repressor proteins.

The mRNA produced by transcription of DNA consists of exons and introns. The removal of introns and joining of exons to obtain mature mRNA is called splicing. It is followed by capping and tailing.

The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available.

Expression of gene starts with transcription of particular segment of DNA, so primary control of gene expression takes place at the level of transcription of DNA into m-RNA.

In lac operon concept the sequence of arrangement of structural gene is as lac Z, lac Y and lac A. The z gene codes for beta-galactosidase. The y gene code for permease and a gene encodes a transacytylase.

During transcription of m-RNA, removal of RNA polymerase III form nucleoplasm will affect the synthesis of t-RNA. The t-RNA transfers the amino acids to the site of translation to form protein.

Human protein can be produced in bacteria by genetic engineering because genetic code is universal i.e. same codon in different organism’s code for same amino acids.