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Year 10 - Science

Alleles, genotype, and phenotype

Inheritance, genotype and phenotype

Unit Summary

This unit covers key genetic terms, single-gene inheritance, and genetic crosses, including probability and ratios. It explores how most traits result from multiple genes and sex determination in humans. The unit also includes interpreting data and using models to solve problems.

Lesson Summary

You will learn to explain how the genotype affects the phenotype of an organism.

Key Notes

  • An individual inherits two copies of each gene in a pair of chromosomes.
  • Versions of genes are called alleles, they can be recessive or dominant, indicated with a capital or lowercase letter.
  • The combination of alleles that an organism has is called its genotype.
  • Different alleles of a gene are associated with different versions of the same characteristic called the phenotype.
  • Some phenotypes are determined only by genotype, others are also affected by the environment.

Vocabulary To Learn

  • allele: A genetic variant in a gene creates an allele (a different version of the gene), which produces a different phenotype.
  • dominant: One or both dominant alleles in the genotype for the characteristic to be expressed in the phenotype.
  • recessive: Two recessive alleles in the genotype for the characteristic to be expressed in the phenotype.
  • genotype: The combination of alleles an organism has for a characteristic (i.e. phenotype).
  • phenotype: Features that result, at least partly, from the genetic code of an organism's genes.

Common Mistakes To Avoid

  • A dominant condition is 'stronger' and that only the strongest characteristic is inherited from one parent.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

An individual inherits two copies of each gene in a pair of chromosomes. Versions of genes are called alleles, they can be recessive or dominant, indicated with a capital or lowercase letter.

2. Define this scientific word and use it in context. 'allele'

A genetic variant in a gene creates an allele (a different version of the gene), which produces a different phenotype. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: A dominant condition is 'stronger' and that only the strongest characteristic is inherited from one parent. Correction: Two genes are inherited, so both alleles contribute to the genotype. In some cases one is dominant and therefore will always be expressed (through protein structure) in the phenotype, the recessive allele is still present.

More Lessons In This Unit

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