(a) Write the F₂ phenotypic ratio of Mendelian dihybrid cross. Name and state the law that explains this phenotypic ratio.

(b) Differentiate between pleiotropy and polygenic inheritance with the help of one example of each.

OR

(a) Name the components of a nucleoside. How does a nucleoside become a nucleotide thatpolymerizes to form a DNA polynucleotide?

(b) Explain the complementary base pairing existing in this chain.

(c) What do 5’ and 3’ ends in a polynucleotide chain refer to?

(a) Phenotypic ratio of Mendelian dihybrid cross is-

9:3:3:1.

Law of independent assortment explains the dihybrid phenotypic ratio. It states-

When two pairs of alleles are present together in a hybrid, the segregation of one pair of the allele is independent of the other pair.

(b) Difference between pleiotropic and polygenic inheritance are-

OR

(a) The components of a nucleoside are- Nitrogenous base (Adenine, Guanine, Thymine, and Cytosine) and pentose sugar.

When a phosphate group is added to the 5’ –OH position of the nucleoside through phosphoester linkage, a nucleoside becomes the corresponding nucleotide which polymerizes to form a DNA polynucleotide.

(b) The complementary base pairing is that, Adenine is bonded to Thymine with the help of two H-bonds. Whereas, Guanine is bonded to Cytosine with the help of 3 H-bonds.

(c) It refers to the fact that the 5’ carbon of the sugar is attached to a phosphate group and the 3’ carbon of the sugar is attached to the hydroxyl group.