Homozygosity is achieved through:

The correct answer is Option (3) → Inbreeding

Option (1) Recombinant DNA technology — Incorrect. It inserts a foreign gene into an organism. It adds a new gene; it does not make the existing genes alike in pairs.

Option (2) Vaccination — Incorrect. Vaccination gives immunity against a disease by introducing inactivated or weakened pathogens. It does not change the genes.

Option (3) Inbreeding — Correct. Inbreeding is the mating of closely related individuals for 4–6 generations; it is used to develop pure lines.

Option (4) Hybridoma technology — Incorrect. A hybridoma is a fused cell (an antibody-making B cell with a cancer cell) used to make monoclonal antibodies. It is not a breeding method.

Note: This question is from Chapter 9, Strategies for Enhancement in Food Production, of the pre-rationalised NCERT book. This chapter is not in the present NCERT book (2026-27). The extract below is from the pre-rationalised edition.

NCERT Extract (Pre-rationalised edition, Chapter 9, Strategies for Enhancement in Food Production):
Animal Breeding – “… Try to recollect the homozygous purelines developed by Mendel as discussed in Chapter 5. A similar strategy is used for developing purelines in cattle as was used in case of peas. Inbreeding increases homozygosity. Thus inbreeding is necessary if we want to evolve a pureline in any animal. Inbreeding exposes harmful recessive genes that are eliminated by selection.”