Principles of Inheritance and Variation quiz

The number of pairs of contrasting traits studied by Mendel in pea was:

The phenotypic ratio of a dihybrid cross in F2 is:

A cross between an F1 hybrid and its recessive parent is called:

Flower colour in snapdragon shows:

The number of possible genotypes for the human ABO blood groups is:

In birds, the female is:

Sickle-cell anaemia is caused by substitution of:

Klinefelter's syndrome has the karyotype:

Which of the following is an X-linked recessive disorder?

The chromosomal theory of inheritance was proposed by:

Why did Mendel choose the garden pea for his experiments? Give two reasons. (2 marks)

Explain codominance with reference to the ABO blood group. (2 marks)

What is pleiotropy? Give one example. (2 marks)

Why is human skin colour an example of polygenic inheritance? (2 marks)

Distinguish between linkage and recombination. (2 marks)

Why are haemophilia and colour blindness more common in males than in females? (2 marks)

What is phenylketonuria? How is it inherited? (2 marks)

State two symptoms of Down's syndrome and its cause. (2 marks)

Distinguish between alpha thalassemia and beta thalassemia with respect to the chromosomes involved. (2 marks)

What did Henking observe in insects, and what was the structure later called? (2 marks)

In a monohybrid cross, 1,200 F2 plants were obtained. Calculate the expected numbers of homozygous dominant, heterozygous and homozygous recessive plants. (3 marks)

A plant heterozygous for two genes (AaBb) is test crossed with aabb. Calculate the expected numbers of each phenotype among 400 offspring if the genes assort independently. (3 marks)

Two genes in Drosophila show 20% recombination. In a test cross producing 1,000 offspring, calculate the expected numbers of parental and recombinant types. (3 marks)

A woman carrier of haemophilia marries a normal man. Calculate the probability that their first child will be (i) a haemophilic son (ii) a carrier daughter (iii) a son with normal blood clotting. (3 marks)

A child has blood group O, and the mother has group A. What are the possible genotypes of the father? If the father's group is B, what is the probability that the couple's next child will have group AB? (3 marks)

Read the passage and answer the questions. In a family, a normal couple has a son with sickle-cell anaemia. Their daughter is healthy. The doctor explains that the disease is autosomal recessive. (i) What are the genotypes of the parents? (ii) What is the probability that the daughter is a carrier? (iii) Explain the change in the haemoglobin molecule in an affected person. (5 marks)

Read the passage and answer the questions. In a pedigree, an affected father and a normal mother have four children. All the daughters are affected and none of the sons is affected. The pattern is repeated in the next generation. (i) What type of inheritance does this suggest? (ii) Explain the reasoning. (iii) What would be the outcome if an affected son married a normal woman? (5 marks)

Read the passage and answer the questions. A girl is short in stature, has rudimentary ovaries and lacks secondary sexual characters. Her karyotype shows 45 chromosomes. (i) Name the disorder. (ii) What is its chromosomal cause? (iii) How does it arise during gamete formation? (5 marks)

Read the passage and answer the questions. In honeybees, the queen lays both fertilised and unfertilised eggs. Fertilised eggs develop into females (queen or workers) and unfertilised eggs into males (drones). (i) Name this type of sex determination. (ii) How many chromosomes do females and males have? (iii) How do drones produce sperms? (5 marks)

Read the passage and answer the questions. A plant breeder crossed tall pea plants with violet flowers (TtVv) with dwarf plants with white flowers (ttvv). She obtained 410 tall violet, 395 dwarf white, 98 tall white and 97 dwarf violet plants. (i) Are the genes linked? Give a reason. (ii) Calculate the recombination frequency. (iii) What does this frequency tell us about the distance between the genes? (5 marks)

Explain the monohybrid cross with a labelled diagram and Punnett square. Derive the law of segregation and the law of dominance from it. (6 marks)

Explain the dihybrid cross with a Punnett square and derive the law of independent assortment. (6 marks)

Explain linkage and recombination using Morgan's Drosophila experiments, with a labelled diagram of the crosses. (6 marks)

Describe the mechanisms of sex determination in humans, Drosophila, grasshoppers, birds and honeybees with labelled diagrams. (6 marks)

What is pedigree analysis? Draw pedigree charts showing (i) an autosomal recessive trait and (ii) an X-linked recessive trait. Explain the features of each. (6 marks)