Question

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40. Distinguish between single gene and polygenic inheritance. Give examples. 41. Explain main steps in DNA recombinant technology 42. Explain inheritance by multiple alleles. 43. Explain one gene one enzyme polypeptide hypothesis.

Answer 1

40. Single gene inheritence is the related to the one gene pair that is two alleles. The Mendelian inheritence is the examle of single s=gene inheritence. In such inheritence one of the allele of gene pair comes from mother and one from father

On the other hand the polygenic inheritence is quantitative inheritence in which one phenotypic character inherited by offspring is governed by two or more than two genes. each of these genes responsible for the inherited characters have equal nfluence as well as has additive effect on the resultant phenotypic character.

41. DNA recombinant technology: It is an excellent technology to modify the genetic makeup of an organism by adding or deleting the DNA of two organism.

It consist of mainly following steps:

a. To identify and isolate the gene of interest to be inserted with the help of restriction enzyme that cut the DNA from specific site followed by isolating the desired gene with the help of available DNA isolation protocols based upon the source of DNA.

b. Cutting the DNA of host where the insert is to be placed with the help of base specific restricton enzymes.They are specific enzymes cut the DNA when and wherever required.

c. Amplification of the desired fragmented gene with the help of PCR and agarose gel electrophoresis.

d. Ligation of the DNA fragment into the appropriate vector, having high copy number. It will be fulfilled by the ligase enzyme.

e. Insertion of this recombinant DNA into the host where the replication can take place.

f. Culture the organism in order to get the large scale amount of recombinant product.

42. This is a non mendelian type of inheritence that involve more than two alleles(which is a typical case of Mendelian inheritence) encoding some particular and unique trait. It means that in such cases the resultant trait is obtained by the combinatorial effect of the two alleles recessive and dominant and there is a mix of types of dominance patterns. Human ABO blood type is an example of multiple alleles.

43. One gene one enzyme hypothesis: Beadle and Tatum discovered this hypothesis, according to which the every gene is specific for the production of specific enzyme. In this hypothesis it was discovered that the gene is directly or indirectly involve in the production of one gene that involves in the metabolic pathway.