Principle of inheritance and variation practice · Easy

Option D (Both (1) and (3) are correct) is correct because a gene can be considered one pair of alleles and is present in allelic form on homologous chromosomes.

Option D (gynadromorph) is correct because a gynandromorph is an organism that contains both male and female characteristics.

Option B (Colour blindness) is correct because color blindness is a sex-linked recessive disorder, meaning the gene responsible is located on the X chromosome.

The correct answer is B ($1:2:1$) because in the F2 generation of a monohybrid cross, the genotypic ratio is 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive.

Option B (22 pairs) is correct because human females have 46 chromosomes in total, with 2 sex chromosomes (XX) and 44 autosomes, which is 22 pairs of autosomes.

Option A (Male heterogamety) is correct because in both XO and XY systems, males produce two different types of gametes (X or O, and X or Y, respectively).

Option A (Antigen-A and antibody-b) is correct because a person with blood group A has antigen A on their red blood cells and antibody b in their plasma.

Option A (Gene for eye colour and gene for wing size) is correct because genes that show a higher percentage of recombination are located farther apart on the chromosome.

Option A (Always expressed in male) is correct because males have only one X chromosome, so any recessive gene on that X chromosome will be expressed.

Option A (Trisomy of chromosome 21) is correct because the described symptoms are characteristic of Down syndrome, which is caused by trisomy 21.

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

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

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

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 (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 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.

Option B (her father and maternal grand father were colour blind) is correct because a colourblind girl must inherit one X chromosome with the colourblindness allele from her father (who must therefore be colourblind) and one from her mother (who must therefore be at least a carrier, inheriting the allele from her father, the maternal grandfather).

Option B (Development of multiple sets of chromosomes) is correct because polyploidy results in an increased number of chromosome sets, leading to rapid speciation.

Option B (Providing a mechanism that explains patterns of inheritance) is correct because Mendel's most significant contribution was establishing the fundamental principles and mechanisms governing how traits are passed from parents to offspring.

The correct answer is B (Features of offspring are not intermediate) because Mendel's observations showed that offspring traits were not a blend of parental traits, refuting the blending theory of inheritance.

Option D (All of these) is correct because a mutation can change the genotype, phenotype, and metabolism of an organism.

Option A (Dwarf stem) is correct because dwarfism is a recessive trait, meaning it only expresses in the homozygous recessive condition.

Option D (II and IV) is correct because Down's syndrome and Turner's syndrome are chromosomal disorders.