Heredity quiz

In Mendel's monohybrid cross, the phenotypic ratio in the F2 generation is:

The genotype of a heterozygous tall pea plant is:

In a dihybrid cross, the F2 phenotypic ratio is:

A human female has the sex chromosomes:

The sex of a child in humans is determined by:

Which of the following is a contrasting pair of traits studied by Mendel?

The F1 progeny of a cross between pure tall and pure dwarf pea plants is:

Genes are made up of:

The genotypic ratio in the F2 generation of a monohybrid cross is:

In some animals such as certain reptiles, the sex of the offspring is determined by:

If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier? Explain. (2 marks)

How do Mendel's experiments show that traits may be dominant or recessive? (2 marks)

How do Mendel's experiments show that traits are inherited independently? (2 marks)

Why is the probability of having a boy or a girl equal in each pregnancy in humans? (2 marks)

What is the role of DNA in heredity? (2 marks)

Why did Mendel get only tall plants in the F1 generation of a cross between tall and dwarf plants? (2 marks)

What is meant by a pure-breeding (true-breeding) plant? (2 marks)

Explain how the dwarf trait reappeared in the F2 generation though it was absent in the F1 generation. (2 marks)

How does a change in a single gene affect the height of a plant? Explain with the example of a growth hormone. (2 marks)

What are the gametes produced by a plant with genotype RrYy? List all of them. (2 marks)

Mendel's results for seed shape in the F2 generation were 5474 round and 1850 wrinkled seeds. Calculate the ratio of round to wrinkled seeds (to two decimal places) and the percentage of round seeds. (3 marks)

A heterozygous tall plant (Tt) is crossed with a dwarf plant (tt). Show the cross and calculate the expected numbers of tall and dwarf plants among 240 offspring. (3 marks)

In a dihybrid F2 generation of 320 plants from a cross of RRYY x rryy, how many are expected to have (i) round green seeds (ii) wrinkled yellow seeds (iii) at least one dominant trait? (3 marks)

In a hospital, 1000 babies were born in a year, of which 512 were boys. Calculate the percentage of boys and girls, and explain why the numbers are close to 50% each. (3 marks)

Two pea plants, both with round yellow seeds and genotype RrYy, are crossed. What fraction of the offspring are expected to be (i) round yellow (ii) wrinkled green? If 160 offspring are produced, how many are expected in each of these two classes? (3 marks)

Read the passage and answer the questions. Mendel crossed pea plants having round and yellow seeds with plants having wrinkled and green seeds. All the F1 plants had round and yellow seeds. When the F1 plants were self-pollinated, the F2 generation showed four types of seeds, including two new combinations not seen in the parents. (i) Which traits are dominant? Give a reason. (ii) Name the two new combinations seen in the F2 generation. (iii) What does this experiment show about the inheritance of two traits? (5 marks)

Read the passage and answer the questions. A farmer has a variety of tall pea plants and wants to know whether they are pure tall (TT) or hybrid tall (Tt). An agricultural scientist advises him to cross them with dwarf plants. (i) What results would he get if the tall plants were TT? (ii) What results would he get if they were Tt? (iii) Why is a dwarf plant used for this test? (5 marks)

Read the passage and answer the questions. In human beings, women have a perfect pair of sex chromosomes, both called X. Men have a mismatched pair in which one is a normal-sized X and the other is a short Y chromosome. Some people blame the mother for the birth of only girls in a family. (i) What gametes can a woman produce with respect to sex chromosomes? (ii) What gametes can a man produce? (iii) Explain why it is wrong to blame the mother for the sex of the child. (5 marks)

Read the passage and answer the questions. Bacteria in a colony reproduce by binary fission. A few bacteria in the colony have a slight variation that allows them to survive at higher temperatures. During a heat wave, most of the colony dies but these few survive and multiply. (i) How did the variation arise in an asexually reproducing population? (ii) Why did these bacteria survive the heat wave? (iii) What would be the effect of this on the next generations of the colony? (5 marks)

Read the passage and answer the questions. Ria has attached earlobes while both her parents have free earlobes. Her teacher explains that free earlobes are dominant over attached earlobes. (i) Using the letters F and f, write the genotypes of Ria and her parents. (ii) Show the cross between her parents. (iii) What is the probability that Ria's younger brother also has attached earlobes? (5 marks)

Describe Mendel's monohybrid cross between tall and dwarf pea plants up to the F2 generation. Draw a checkerboard, write the phenotypic and genotypic ratios, and explain the conclusions Mendel drew about dominant and recessive traits. (6 marks)

Describe Mendel's dihybrid cross between pea plants with round yellow seeds and wrinkled green seeds. Draw the checkerboard for the F2 generation and explain how the 9 : 3 : 3 : 1 ratio shows the independent inheritance of traits. (6 marks)

Explain how traits are expressed with the example of plant height controlled by a gene for an enzyme that makes a growth hormone. Draw a flow chart from DNA to trait. Explain how both parents contribute equally to the genetic material of the offspring through germ cells with one set of genes. (6 marks)

Explain sex determination in human beings with a labelled flow diagram showing the parents, gametes and children. Why is the ratio of boys to girls born close to 1 : 1? Mention one way in which sex is determined in some other animals. (6 marks)

What is variation? Explain how variations accumulate during reproduction, with a diagram showing how variations build up over successive generations of asexual and sexual reproduction. Why do great variations occur in sexual reproduction, and what is their significance? (6 marks)