Study the schematic representation of the genes involved in the lac operon given below and answer the questions that follow:

(a) Identify and name the regulatory gene in this operon. Explain its role in ‘switching off’ the operon.

(b) Why is the lac operon’s regulation referred to as negative

regulation?

(c) Name the inducer molecule and the products of the genes ‘z’ and ‘y’ of the operon. Write the functions of these gene products.

OR

(a) How does the Hardy-Wienberg equation explain genetic equilibrium?

(b) Describe how this equilibrium is disturbed that may lead to founder effect.

a) The lac operon contains one regulatory gene which is the i gene codes that for the repressor of the lac operon. The i gene synthesized the repressor of the operon.The repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon that results in switch off of the operon.

b) Regulation of lac operon by a repressor is referred to as negative regulation.

c) Lactose is the inducer molecule. The z gene codes for beta-galactosidase (β-gal), which is primarily responsible for the hydrolysis of the disaccharide, lactoseinto its monomeric units, galactose, and glucose. The y gene codes for permease, which increases the permeability of the cell to β-galactosides.

OR

(a) How does the Hardy-Wienberg equation explain genetic equilibrium?

(b) Describe how this equilibrium is disturbed that may lead to founder effect.

a) Hardy-Wienberg states that the allelic frequencies in a population are stable and constant from generation to generation. The total genes and their alleles in a population which is gene pool remains a constant. This is called genetic equilibrium. The total sum of all the allelic frequencies is 1. p2+2pq+q2=1 is a binomial expansion of (p+q)2. When frequencymeasured, differs from expected values, the difference (direction) indicatesthe extent of evolutionary change.

b) The five factors are known to affect Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination, and natural selection.

When the migration of a section of the population to another place and gene frequencies change in the original as well as in the new population.New genes/alleles are added to the new population and these are lost from the old population.If this gene migration, happens more times then there will be a gene flow and the genetic drift is when the same change occurs by chance.Sometimes the change in allele frequency is different in the new sample of the population so that they become a different species. The original drifted population results as founders and the effect are called founder effect.