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CAIE IGCSE Biology 18.1.4 Genetic & Environmental Causes of Variation

Practise distinguishing variation caused mainly by genes from variation influenced by both genes and the environment.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • state that discontinuous variation is usually caused by genes only
  • state that continuous variation is usually caused by both genes and environmental factors
  • classify examples such as blood group and body mass by both pattern and cause

18.1.4—Discontinuous variation is usually question 1

[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 FB\mathbf{F}^{\mathbf{B}} and the allele for white feathers is FW\mathbf{F}^{\mathbf{W}}.

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

Fig. 5.1

Fig. 5.1

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

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