🧬 Genetics & Heredity — Practice Worksheet

Q1. Mendel's law of segregation is also known as:

1. Law of dominance
2. Law of purity of gametes
3. Law of independent assortment
4. Law of inheritance

Q2. In a monohybrid cross Tt × Tt, the phenotypic ratio of the F₂ generation is:

1. 1 : 1
2. 3 : 1
3. 1 : 2 : 1
4. 9 : 3 : 3 : 1

Q3. A cross between a homozygous tall plant (TT) and a homozygous dwarf plant (tt) produces:

1. All tall plants
2. All dwarf plants
3. 50% tall and 50% dwarf
4. 75% tall and 25% dwarf

Q4. Colour blindness in humans is a:

1. Y-linked trait
2. X-linked recessive trait
3. Autosomal dominant trait
4. Autosomal recessive trait

Q5. The blood group system in humans is an example of:

1. Incomplete dominance
2. Co-dominance and multiple alleles
3. Epistasis
4. Polygenic inheritance

Q6. Down syndrome is caused by trisomy of chromosome:

1. 18
2. 21
3. 13
4. X

Q7. The chromosomal constitution of Turner syndrome is:

1. 47, XXY
2. 45, X0
3. 47, XXX
4. 47, XYY

Q8. Crossing over occurs during which stage of meiosis?

1. Leptotene
2. Pachytene
3. Diplotene
4. Diakinesis

Q9. In incomplete dominance, the F₂ phenotypic ratio of a monohybrid cross is:

1. 3 : 1
2. 1 : 2 : 1
3. 9 : 3 : 3 : 1
4. 1 : 1

Q10. The test cross is used to determine:

1. The phenotype of an organism
2. The genotype of a dominant phenotype organism
3. The number of chromosomes
4. The sex of an organism

Q11. Sickle cell anaemia is caused by a point mutation in the gene coding for:

1. α-globin chain
2. β-globin chain
3. γ-globin chain
4. δ-globin chain

Q12. Linkage was first experimentally demonstrated by:

1. Mendel
2. Morgan
3. Bateson and Punnett
4. De Vries

Q13. In a dihybrid cross between two heterozygous parents (RrYy × RrYy), calculate the expected phenotypic ratio and the number of offspring with both recessive traits out of 256 progeny.

Q14. A colour-blind man marries a carrier woman. Show the cross and determine the probability of their children being colour-blind.

Q15. In a population, the frequency of the recessive allele (q) for albinism is 0.1. Using the Hardy-Weinberg equation, calculate the frequency of carriers (heterozygotes) in the population.

Q16. Explain the inheritance pattern of ABO blood groups. A man with blood group A (heterozygous) marries a woman with blood group B (heterozygous). What are the possible blood groups of their children?

Q17. Differentiate between complete linkage and incomplete linkage. If two genes are 20 cM apart on a chromosome, what is the recombination frequency?

Q18. A plant with genotype AaBbCc is self-pollinated. If all three genes assort independently, how many different genotypes and phenotypes are possible in the offspring?

Q19. Explain the chromosomal theory of inheritance. How did Morgan's experiments with Drosophila provide evidence for sex-linked inheritance?

Q20. A couple has a child with phenylketonuria (PKU), an autosomal recessive disorder. Neither parent shows the disease. What are the genotypes of the parents? What is the probability that their next child will have PKU?