TN State Board 12th Zoology Question Paper 2026

Arrhenotoky is the type of parthenogenesis in which only males are produced, usually from unfertilized eggs. In thelytoky, only females are produced. Amphitoky can produce both sexes depending on conditions. Therefore, the correct choice is (a) Arrhenotoky.

Statement I is correct: surgical removal of the testes is called orchidectomy. Statement II is not correct: orchidectomy does not lead to difficulty in urination; it mainly affects male reproductive functions and hormone production. Therefore, the correct answer is (d) Statement I is correct and Statement II is not correct.

Hormonal contraceptive pills work mainly by inhibiting ovulation, altering the uterine endometrium, and changing cervical mucus so sperm passage is difficult. They do not inhibit spermatogenesis, because spermatogenesis occurs in males, not in users of these pills. Hence, the incorrect action is (b) Inhibition of spermatogenesis.

The given pedigree symbol represents dizygotic twins. In pedigree charts, monozygotic twins are usually shown by twin lines with an additional connecting line between them, while dizygotic twins are shown as two branches from the same point without that connecting line. Therefore, the correct answer is (d) Dizygotic twins.

Hershey and Chase’s bacteriophage experiment proved that DNA is the genetic material. They used radioactive phosphorus to label DNA and radioactive sulphur to label protein, and found that only DNA entered the bacterial cell and directed formation of new phages. Thus, the correct answer is (d) DNA is the genetic material.