2.Mendel’s monohybrid ratio is outcome of
(1) Independent assortment of genes
(2) Hardy-Weinberg law
(3) Uncontrolled matting
(4) Separation of homologous chromosomes during meiosis

Explanation:

In a monohybrid cross, F1 individuals are heterozygous (Aa). When they form gametes, the two alleles A and a separate so that each gamete gets only one allele. This is Mendel’s law of segregation and, cytologically, it corresponds to the separation of homologous chromosomes (bearing A or a) during meiosis I. Random fusion of these gametes (A or a) then gives the F2 genotypes AA, Aa, aa in a 1:2:1 ratio, producing a 3:1 dominant:recessive phenotypic ratio.

Option-wise:

1. Independent assortment of genes

• Independent assortment refers to how alleles of different genes (on different chromosome pairs) assort independently, giving the 9:3:3:1 ratio in dihybrid crosses, not the 3:1 ratio of a single gene.

2. Hardy–Weinberg law

• This law describes genotype frequencies in large, randomly mating populations at equilibrium (p², 2pq, q²). It is a population‑genetic principle, not the cause of Mendel’s monohybrid segregation in a controlled cross.

3. Uncontrolled mating

• Mendel’s experiments used controlled matings (planned crosses), not uncontrolled mating. The ratio is determined by allele segregation, not by randomness of partners.

4. Separation of homologous chromosomes during meiosis – correct

• Each homolog carries one allele (A or a). When homologous chromosomes segregate in meiosis I, alleles separate into different gametes. This cytological event underlies Mendel’s law of segregation and directly produces the monohybrid 3:1 ratio.