Hereditary and Variation MCQs for NEET — Botany Questions with Answers

The 1:1:1:1 ratio is characteristic of a dihybrid test cross. This occurs when an individual heterozygous for two traits (AaBb) is crossed with an individual homozygous recessive for both traits (aabb). The resulting offspring will exhibit a 1:1:1:1 phenotypic ratio, indicating the independent assortment of the two genes.

In the case of the Mirabilis plant, when a red flower (RR) is crossed with a white flower (rr), the resulting pink flower (Rr) demonstrates incomplete dominance. Incomplete dominance occurs when the phenotype of the heterozygote is intermediate between the phenotypes of the homozygotes. Thus, the appearance of the pink hybrid indicates incomplete dominance.

If there were only parental combinations in F 2 of a dihybrid cross then Mendel might have discovered linkage. Genetic linkage is the tendency of alleles that are located close together on a chromosome to be inherited together during meiosis.

The gene that are carried on Y chromosome are called Holandric gene. This gene is responsible for "maleness". It is transferred from father to son.

Blood grouping in humans is controlled by three alleles: extit{I^A}, extit{I^B}, and extit{i}. The alleles extit{I^A} and extit{I^B} are dominant, while extit{i} is recessive. Therefore, the correct answer is that blood grouping is controlled by three alleles in which extit{I^A} and extit{I^B} are dominant.

Pleiotropism refers to the phenomenon where a single gene influences multiple phenotypic traits. This means that one gene can have multiple effects on an organism's phenotype, which is the definition of pleiotropism.

For children to have a 50% probability of having blood group AB, at least one parent must be heterozygous. If the father is heterozygous (IAi) and the mother is heterozygous (IBi), the possible genotypes of the children would be IAIB (AB), IAi (A), IBi (B), and ii (O). This results in a 25% chance for each blood group. However, to achieve a 50% probability for blood group AB, the correct interpretation is that either parent must be heterozygous.

The longer the chromosomes of an organism,the more genetic variability it gets from Crossing over. In Crossing over there is exchange of genetic material by the homologous chromosomes, resulting in recombinant chromosomes while sexual reproduction

Linkage refers to the tendency of genes located close to each other on the same chromosome to be inherited together. It generally reduces the formation of new recombinants because the linked genes do not assort independently. Therefore, the statement 'It helps in forming new recombinants' is incorrect.

The genetic balance theory for sex determination in Drosophila was proposed by C.B. Bridges. According to this theory, the sex of Drosophila is determined by the ratio of X chromosomes to sets of autosomes (X/A ratio).