Which one of the following generates new genetic combinations leading to variation?
(1) Vegetative reproduction
(3) Sexual reproduction
(4) Nucellar polyembryony
(3) The sexual reproduction brings about variation through genetic recombinations.
First of all genetic recombination occurs in non-homologous chromosomes during crossing over of pachytene stage in meiotic cell division.
Secondly, the random union of gametes also contributes in forming new combinations of characters. Other options (1) (2) and (4) do not contribute in the formation of proganies with new variations.
Vegetative reproduction occurs through vegetative parts of organisms (oplants). Parthenogenesis is formation of new individual without fertilisation (e.g., frog).