Principle of inheritance and variation practice · Mixed difficulty

Option B (Haploid - diploid sex - determination system) is correct because in haplodiploidy, males are haploid (have no father) and females are diploid (have a father and can have sons).

Option C (Both (a) and (b)) is correct because codominance is observed in both plants and animals.

Option C ($9\mathrm{ }:\mathrm{ }3\mathrm{ }:\mathrm{ }3\mathrm{ }:\mathrm{ }1$) is correct because even though the genes are linked, some crossing over will still occur, leading to a modified dihybrid ratio that approximates 9:3:3:1, especially if the genes are not extremely tightly linked.

Option B (Genetic drift) is correct because the founder effect is a specific type of genetic drift where a small group establishes a new population.

The correct answer is B (Probable result of a cross) because a Punnett square is used to predict the possible outcomes of a genetic cross, not the definite result.

Option A (a direct relationship) is correct because the greater the distance between genes, the higher the percentage of recombination due to increased chances of crossing over.

Option C (Provides immunity against malaria) is correct because individuals with sickle cell trait (heterozygous) are more resistant to malaria, providing a selective advantage in malaria-prone regions.

Option B (heterozygous and green) is correct because the ratio of 760 green pod and 240 yellow pod plants (approximately 3:1) suggests a heterozygous parent (Gg) with green pods, where green is dominant over yellow (gg).

Option C (Chlorinated hydrocarbons) is correct because chlorinated hydrocarbons are known mutagens, meaning they can cause mutations in DNA.

Option B ($\frac{6}{16}$) is correct because it represents the probability of obtaining tall pink offspring from a dihybrid cross.

Option B (Type O) is correct because individuals with blood type O are universal donors and can donate blood to individuals with any ABO blood type in emergencies.

Option B (Pleiotropic genes) is correct because pleiotropic genes are defined as genes that have multiple effects on an organism's phenotype.

Option C (15) is correct because in a polygenic cross, the coefficients of the binomial expansion represent the phenotypic ratios.

Option D (Polygenic inheritance) is correct because skin color in humans is controlled by multiple genes, each contributing additively to the phenotype, which is the definition of polygenic inheritance.

Option D (Sex –linked recessive) is correct because the disease appears in 3 out of 5 sons, while neither of the daughters are affected, suggesting X-linked recessive inheritance where carrier mothers pass it to their sons.

Option C (Colour blindness) is correct because Haemophilia and Colour blindness are both X-linked recessive disorders.

Option D (Brown body, white eyes) is correct because y+ represents the wild-type allele for body color (brown), and w represents the mutant allele for eye color (white).

Option B (Yy $\times$ Yy) is correct because a cross between two heterozygotes (Yy) results in a 1:2:1 genotypic ratio (YY:Yy:yy) and, assuming incomplete dominance, a corresponding phenotypic ratio.

Option B (Sex-linked recessive disorders) is correct because both colorblindness and hemophilia are caused by recessive genes located on the X chromosome.

Option A (Cretinism) is correct because Cretinism is caused by iodine deficiency and is not a hereditary disease, while the others are.

The correct answer is B (1:1 and 1:1) because both the genotypic and phenotypic ratios of a back cross and test cross of a Mendelian monohybrid are 1:1.

Option A (Klinefelter’s syndrome –44 autosomes + XXY) is correct because Klinefelter's syndrome is characterized by the presence of an extra X chromosome in males, resulting in an XXY karyotype.

Option A (Both (A) & (R) are true and the (R) is the correct explanation of the (A)) is correct because Mendel's success in formulating the laws of segregation and independent assortment was partly due to the fact that the seven traits he studied were located on different chromosomes, allowing for independent assortment.

Option D (42370) is correct. This question is flawed as it provides an impossible context (selfing a heterozygous plant and asking for a specific offspring count). The correct approach would involve calculating the probability of the homozygous recessive offspring (1/16) and multiplying by the total population size, but the provided options are not realistic.

Option A (Turner’s syndrome) is correct because XO chromosomal abnormality in humans results in Turner's syndrome.

Option D (Man and rhesus monkey only) is correct because the Rh factor was first discovered in rhesus monkeys and is also present in humans.

Option D (Archibald Garrod) is correct because he is recognized as the father of physiological genetics or biochemical genetics due to his work on inborn errors of metabolism.

Option C (They may have daughters who are colourblind or haemophilic) is correct because the daughters can inherit different combinations of the X chromosomes carrying the colourblindness and haemophilia genes from their parents, leading to some daughters being colourblind, some haemophilic, some both, and some neither.

Option C (Fowl) is correct because in birds (like fowl), the female is the heterogametic sex (ZW) while the male is homogametic (ZZ).

The correct answer is C (Punnett square) because a Punnett square is a diagram used to predict the genotypes and phenotypes of offspring in a genetic cross.