TN State Board 12th Botany Question Paper 2023

Exonuclease removes nucleotides from the ends (termini) of DNA molecules. Endonuclease cuts DNA at specific internal sites (middle). Alkaline Phosphatase removes phosphate groups (or adds them in some biochemical contexts, usually associated with removing 5' phosphates to prevent self-ligation). Ligase joins DNA fragments together. Thus, (1)-(iii), (2)-(iv), (3)-(i), (4)-(ii) matches correctly.

Complementary genes involve the interaction of two non-allelic genes where one dominant gene is necessary to express the other, resulting in a phenotypic ratio of 9:7 in the F2 generation. 9:3:3:1 is Mendelian dihybrid, 9:3:4 is recessive epistasis, and 9:6:1 is duplicate gene action.

Dr. M.S. Swaminathan is widely recognized as the 'Father of the Green Revolution in India' for his role in introducing and developing high-yielding varieties of wheat and rice.

The functional megaspore is the first cell of the female gametophyte (embryo sac) in angiosperms, as it undergoes mitosis to form the mature gametophyte.

Ozone ($O_3$) in the stratosphere acts as a shield against harmful ultraviolet (UV) radiation. Its depletion leads to increased UV penetration, which is linked to an increased risk of skin cancer in humans.