Principle of inheritance and variation practice · Easy

Option C (The son of the carrier woman has $50\%$ chances of being colour blind) is correct because color blindness is an X-linked recessive trait, and a carrier mother has a 50% chance of passing the affected X chromosome to her son.

Option C (Both (1) and (2)) is correct because blood grouping demonstrates both multiple alleles (A, B, O) and codominance (A and B are both expressed in AB blood type).

Option B (1 in 4) is correct because if both parents are heterozygous carriers for albinism (Aa), the probability of having an albino child (aa) is 1/4.

Option A (Genetic recombination) is correct because sexual reproduction involves the fusion of gametes, leading to the shuffling of genes and creating new combinations of alleles.

Option B ($1\mathrm{ }:\mathrm{ }2\mathrm{ }:\mathrm{ }1$) is correct because in incomplete dominance, the heterozygous genotype results in a distinct phenotype, leading to a 1:2:1 phenotypic ratio in the F2 generation.

Option D (2) is correct because Mendel chose two contrasting characters for pea pod: shape and color.

Option C is correct because Carl Correns was one of the three scientists who independently rediscovered Mendel's work in 1900.

Option D (Both tall and dwarf plants in 3 : 1 ratio) is correct because in the F2 generation of a monohybrid cross (TT x tt), the phenotypic ratio of tall to dwarf plants is 3:1.

Option D (Both A and B are false) is correct because Turner syndrome is due to sex chromosome monosomy, and high temperature can be a physical mutagen.

Option A (Sex-chromosome) is correct because the sex chromosomes (X and Y) determine the genetic sex and identity of a human male.

Option A (Genes) is correct because Mendel used the term \"factor\" to refer to what we now know as genes, the units of heredity.

Option C (4) is correct because there are four conditions exhibiting dissimilar sex chromosomes: XXY (Klinefelter syndrome), XYY, XXX (Triple X syndrome), and XO (Turner syndrome).

The correct answer is B (Violet) because in Mendel's experiments with pea plants, violet flower color was dominant. Therefore, if 'W' represents the dominant allele for violet and 'ω' represents the recessive allele, Wω will express the dominant violet phenotype.

Option A (Recessive) is correct because most mutations are recessive, meaning they are only expressed when homozygous.

Option B ($50 \%$) is correct because the affected mother produces gametes with either an extra chromosome 21 or a normal set, leading to a 50% chance of the offspring inheriting Down's syndrome.

Option D is correct because a Punnett square is a graphical representation used to calculate the probability of all possible genotypes of offspring in a genetic cross.

Option A (AB antigen) is correct because individuals with blood group AB have both A and B antigens on their red blood cells.

Option A (ZZ-ZW) is correct because birds use the ZZ-ZW system for sex determination, where males are ZZ and females are ZW.

Option B (Genotype and environment interactions) is correct because the phenotype is the result of the interaction between an organism's genetic makeup (genotype) and its environment.

Option C (Aneuploidy – due to non-disjunction) is correct because Turner syndrome results from aneuploidy (specifically monosomy X) caused by non-disjunction during meiosis.

Option A (Trisomy) is correct because trisomy refers to the condition where there is an extra copy of a chromosome in a homologous pair.