6.1.7

Genetic Crosses

Test yourself

Punnett Square

Punnett Squares are used to calculate the ratio of offspring phenotypes.

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Dominant alleles

  • Pea plants can be either green or yellow.
  • The green colour allele is dominant over the yellow allele.
  • We represent the dominant green allele with 'G'.
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Recessive

  • The yellow colour allele is recessive.
  • We represent the recessive yellow allele with 'g' on a Punnett square.
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Offspring

  • With one homozygote recessive parent and one heterozygote parent (shown above):
    • There is a 50% chance of offspring being yellow.
    • Ratio of green:yellow offspring will be 1:1
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Jump to other topics

1Cell Biology

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

6Inheritance, Variation & Evolution

7Ecology

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