Botany MCQs for NEET — Practice Questions with Answers

The correct matching is: (1 - c), (2 - d), (3 - a), (4 - b). Here's the reasoning:

1. Single gene inheritance follows a 3:1 ratio.
2. Double gene inheritance follows a 9:3:3:1 ratio.
3. Test cross results in a 1:1:1:1 ratio.
4. Incomplete dominance results in a 1:2:1 ratio.

The correct matching is: (1 - c), (2 - a), (3 - d), (4 - b). Here's the reasoning:

1. Blood group A can have the genotypes IAIA or IAi.
2. Blood group B can have the genotypes IBIB or IBi.
3. Blood group AB has the genotype IAIB.
4. Blood group O has the genotype ii.

The cross between a heterozygous A blood group mother (IAi) and a B blood group father (IBIB or IBi) results in various possible genotypes for the offspring: IAIB (AB blood group), IAi (A blood group), IBi (B blood group), and ii (O blood group). Hence, the expected blood groups of the First filial generation can be A, B, AB, or O. Therefore, the correct answer is not listed in the provided options.

In Drosophila, the sex of the fly is determined by the ratio of X chromosomes to autosomes (X/A ratio). The correct matches are:

1. X/A = 1 corresponds to a normal female (e).
2. X/A = 1.5 corresponds to a super female sterile (d).
3. X/A = 0.67 corresponds to an intersex (c).
4. X/A = 0.33 corresponds to a super male sterile (b).
5. X/A = 0.5 corresponds to a normal male (a).

Assertion (A) is true because chromosomes do undergo segregation and independent assortment according to Mendel's laws. Reason (R) is false because the reduction in chromosome number by half occurs during meiosis, not mitosis. Therefore, (A) is true but (R) is false.

Colourblindness and hemophilia are indeed both X-linked recessive traits, meaning they are carried on the X chromosome and manifest primarily in males. The pedigrees for these conditions will look similar because they follow the same inheritance pattern. Therefore, both the Assertion (A) and Reason (R) are true, and (R) is the correct explanation of (A).

Lack of independent assortment of two genes in Drosophila is due to linkage. Linkage refers to the phenomenon where genes that are located close to each other on the same chromosome tend to be inherited together because they do not assort independently during meiosis.

To determine the proportion of sperms with the genotype abh, we need to consider the segregation of each gene during meiosis. The male is heterozygous for genes A and B (genotype AaBb) and hemizygous for the haemophilic gene (genotype h). The possible combinations for the sperms are AB, Ab, aB, and ab. Since the male is hemizygous for the haemophilic gene, each combination will either have H or h. Therefore, the proportion of sperms with the genotype abh is calculated as follows:
Probability of 'a' = 1/2,
Probability of 'b' = 1/2,
Probability of 'h' = 1/2.
Combining these probabilities: (1/2) * (1/2) * (1/2) = 1/8.

Recessive genes located on the X-chromosome in humans are always expressed in males because males have only one X-chromosome (XY). There is no corresponding allele on the Y-chromosome to mask the effect of a recessive gene on the X-chromosome. In contrast, females have two X-chromosomes (XX), so a recessive gene on one X-chromosome can be masked by a dominant gene on the other X-chromosome.