Question

Choose one topic from the three topics below to discuss: 250+ words

1. What are the interesting differences you can think of between DNA, RNA and protein biosynthesis?
2. Discuss the mechanisms of Lac operon or Trp operon, what do you think are impressive?
3. What interests you the most about genetic code?

Answer 1

2.

The lac operon in bacteria consists of: A promoter(P), an operator(O), a regulatory region(I) and three structural genes encoding Beta galactosidase which breaks lactose to glucose and galactose(Z), Permease which increases permeability of lactose within cells(Y) and transacetylase(A). The operator is present between the promoter and the structural genes. Few molecules of Beta galactosidase converts lactose to allolactose(inducer) which binds to repressor encoded by the lacI gene preventing it from binding to the operator and allowing transcription of the three genes.The repressor binds to the operator in absence of allolactose.It also depends on the availability of the glucose and is regulated by the binding of the CAP-cAMP complex in upstream of promoter. When glucose is high, cAMP is low so the complex cannot bind and the genes are not transcribed and vice versa.

The trp operon consists of: A promoter, an operator and five genes(A,B,C,D,E) needed for the synthesis of Tryptophan.A repressor protein encoded by a seperate operon cannot bind to the operator if Trp is absent leading to the transcription of Trp biosynthesis genes.When Trp is present the repressor binds to it and undergoes a confirmational change allowing it to bind to the operator leading to the repression of transcription.

What is impressive is while lac operon is switched on when lactose is present, trp operon is switched off when Tryptophan is present. Thus the two operons act in an opposite manner. This is due to the difference in functions between the two operons. While lac operon operates for metabolizing lactose, Trp operon operates for the synthesizing Tryptophan.