CAIE IGCSE Biology 18.1 Variation Questions

Practise variation questions by defining variation, classifying continuous and discontinuous traits, and explaining how mutations create new alleles and genetic diversity.

Exam points

define variation and distinguish continuous ranges between two extremes from discontinuous categories with no intermediates
identify body length, body mass, ABO groups, pea seed shape or colour and leaf features as variation examples
explain discontinuous variation as usually genetic and continuous variation as influenced by genes and environment
describe mutation as a genetic change that forms new alleles, not a product of selection or sexual reproduction
describe gene mutation as a random DNA base-sequence change and reject chromosome-number or amino-acid alternatives
state that ionising radiation and some chemicals increase the rate of mutation
identify mutation, meiosis, random mating and random fertilisation as sources of genetic variation

Covered syllabus points

18.1.1—Variation as differences between 18.1.2—Continuous variation results 18.1.3—Discontinuous variation results 18.1.4—Discontinuous variation is usually 18.1.5—Examples of continuous 18.1.6—Mutation as genetic change 18.1.7—Mutation is the way in which new 18.1.8—Ionising radiation and some chemicals 18.1.9—Gene mutation as a random change 18.1.10—Mutation, meiosis, random mating

[Maximum number: 1]

What is a definition of variation?

having two identical alleles of a particular gene

individuals of the same species in one area

differences between individuals of the same species

the way in which new alleles are formed

[Maximum number: 1]

The graph shows the masses of two different types of tomato.

Figure for Question 2 — CAIE IGCSE Biology

What can be concluded from the graph?

Genes do not affect the mass of tomatoes.

Type 1 tomatoes show continuous variation.

Type 2 tomatoes are sometimes smaller than type 1 tomatoes.

Type 2 tomatoes show discontinuous variation.

[Maximum number: 3]

A scientist investigated the inheritance of fur colour in cats.

The gene for coat colour is located on the X chromosome. The gene has two alleles:
- B black
- b orange.

The X chromosome with the allele for black is represented by $\mathbf{X}^{\mathbf{B}}$ .
The X chromosome with the allele for orange is $\mathbf{X}^{\mathbf{b}}$ .
A female cat can be a mixture of these colours, described as calico.
Fig. 3.1 shows the inheritance of this condition in a family of cats.

Fig. 3.1

Coat colour in cats is an example of discontinuous variation.

Explain why coat colour is an example of discontinuous variation.

[Maximum number: 1]

Feather colour in some breeds of chicken is an example of codominance in birds.

In this example, a chicken with white feathers and a chicken with black feathers can breed to produce offspring that have white feathers and black feathers.

The allele for black feathers is $\mathbf{F}^{\mathbf{B}}$ and the allele for white feathers is $\mathbf{F}^{\mathbf{W}}$ .

Fig. 5.1 is a pedigree diagram of a family of chickens.

Fig. 5.1

State the type of variation that is caused by genes only.

[Maximum number: 2]

An ecologist studied variation in a species of xerophyte.

The ecologist also measured other features of the leaves.

Fig. 5.2 shows the variation in leaf feature B.

Fig. 5.2

State two named features of leaves that show the type of variation shown in Fig. 5.2.
1

2

[Maximum number: 1]

Which term is a genetic change?

allele

genotype

mutation

phenotype

[Maximum number: 1]

What is a way in which new alleles are formed?

artificial selection

mutation

natural selection

sexual reproduction

[Maximum number: 2]

Mitosis and meiosis are both important processes for life.

Mutations are a source of genetic variation in a population.

State two examples of how mutation rates can be increased.

1

2

[Maximum number: 2]

Mitosis and meiosis are both important processes for life.

Mutations are a source of genetic variation in a population.

Describe what is meant by a gene mutation.

[Maximum number: 2]

Mutation causes formation of new alleles which increases genetic variation.

State two other sources of genetic variation in populations.
1

2

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Covered syllabus points

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Question 10