Botany MCQs for NEET — Practice Questions with Answers

A heterozygous tall plant (Tt) crossed with a dwarf plant (tt) will produce offspring with the following genotypes: Tt and tt. This results in a 1:1 or 50% ratio of tall to dwarf plants.

Genetic recombinations occur through meiosis and fertilization. During meiosis, homologous chromosomes exchange segments in a process known as crossing over, which creates new combinations of alleles. Fertilization then combines the genetic material from two parents, further increasing genetic diversity.

The unit of inheritance is the gene. A gene is a segment of DNA that contains the instructions for the development, functioning, growth, and reproduction of organisms. Genes are passed from parents to offspring and determine specific traits.

An allele is an alternate form of a gene that arises by mutation and is found at the same place on a chromosome. Alleles can vary in sequence and can result in different traits being expressed.

Genes do not occur in pairs in gametes. Gametes are haploid cells, meaning they contain only one set of chromosomes, and hence only one allele for each gene. In contrast, zygotes, somatic cells, and endosperm cells are diploid or triploid, containing two or more sets of chromosomes, and thus genes occur in pairs in these cells.

Although seeds, in general are the products of fertilisation, a few flowering
plants such as some species of Asteraceae and grasses, have evolved a
special mechanism, to produce seeds without fertilisation, called apomixis

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.