A child has blood group O. His father has blood group A and his mother has blood group B. What are the genotypes of the parents?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Father: IAIA, Mother: IBIB
• Father: IAi, Mother: IBi
• Father: IAIA, Mother: IBi
• Father: IAi, Mother: IBIB
Correct Option: B  [ Father: IAi, Mother: IBi ]

Remark: A child with blood group O has genotype ii. To have this genotype, the child must inherit one 'i' allele from each parent. Since the father is blood group A, his genotype must be IAi. Since the mother is blood group B, her genotype must be IBi.

A diploid organism is heterozygous for 4 loci. How many types of gametes can be produced, assuming independent assortment?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• 4
• 8
• 16
• 32
Correct Option: C  [ 16 ]

Remark: The number of different types of gametes that can be produced by a heterozygous organism is 2^n, where n is the number of heterozygous loci. In this case, n = 4, so the number of gamete types is 2^4 = 16. This is based on the principle of independent assortment for unlinked genes.

Gynaecomastia (development of breast) is a characteristic feature of which genetic disorder?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Down's Syndrome
• Turner's Syndrome
• Klinefelter's Syndrome
• Haemophilia
Correct Option: C  [ Klinefelter's Syndrome ]

Remark: Individuals with Klinefelter's Syndrome (47, XXY) have overall masculine development, but feminine development, such as the development of breast (Gynaecomastia), is also expressed.

In a pedigree chart, what does a square symbol represent?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Affected individual
• Female
• Male
• Mating
Correct Option: C  [ Male ]

Remark: In the standard symbols used in human pedigree analysis, a square represents a male individual.

Alpha Thalassemia is controlled by genes located on which chromosome?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Chromosome 11
• Chromosome 16
• X chromosome
• Y chromosome
Correct Option: B  [ Chromosome 16 ]

Remark: Alpha Thalassemia is controlled by two closely linked genes, HBA1 and HBA2, on chromosome 16 of each parent.

In honey bees, males produce sperms by which type of cell division?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Meiosis
• Mitosis
• Amitosis
• Budding
Correct Option: B  [ Mitosis ]

Remark: Males (drones) in honey bees are haploid and develop by parthenogenesis. Therefore, they produce sperms by mitosis.

Who proposed the chromosomal theory of inheritance?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• T.H. Morgan
• Mendel
• Sutton and Boveri
• Watson and Crick
Correct Option: C  [ Sutton and Boveri ]

Remark: Walter Sutton and Theodore Boveri noted the parallel behavior between chromosomes and genes and used chromosome movement to explain Mendel’s laws. Sutton united this knowledge into the chromosomal theory of inheritance.

Failure of cytokinesis after the telophase stage of cell division results in an increase in a whole set of chromosomes, a phenomenon known as:

[Principles-of-Inheritance-and-Variation] [class-xii ]

• Aneuploidy
• Monosomy
• Trisomy
• Polyploidy
Correct Option: D  [ Polyploidy ]

Remark: Failure of cytokinesis after the telophase stage of cell division results in an increase in a whole set of chromosomes in an organism, and this phenomenon is known as polyploidy. This condition is often seen in plants.

When a cross is made between a tall plant with yellow seeds (TtYy) and a tall plant with green seeds (Ttyy), what proportion of the offspring is expected to be dwarf and green?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• 1/4
• 1/8
• 3/16
• 1/16
Correct Option: B  [ 1/8 ]

Remark: This is a dihybrid cross. Consider each trait separately based on the provided genotypes. The cross for height is Tt x Tt, which produces 1/4 dwarf (tt) offspring. The cross for seed colour is Yy x yy, which produces 1/2 green (yy) offspring. The combined proportion of dwarf and green (ttyy) offspring is the product of these independent probabilities: (1/4) * (1/2) = 1/8.

A child has blood group O. His father has blood group A and his mother has blood group B. What are the possible genotypes of the other offspring?

[Principles-of-Inheritance-and-Variation] [class-xii ]

• A, B, and AB
• Only A and B
• Only AB
• Only O
Correct Option: A  [ A, B, and AB ]

Remark: For the parents to have a child with blood group O (genotype ii), they must both carry the recessive i allele. Therefore, their genotypes are IAi (father) and IBi (mother). A cross between these parents can produce offspring with genotypes IAIB (AB), IAi (A), IBi (B), and ii (O). Thus, the other possible blood groups are A, B, and AB.