Year 10 - Science
Models of single-gene inheritance: family tree diagrams
Inheritance, genotype and phenotype
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
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 construct and interpret family tree diagrams showing information about inheritance of a feature.
Key Notes
- Offspring inherit two alleles, one from each parent, the combination of these alleles is the genotype.
- The phenotypes of members of a family can be shown in a diagram such as a family tree (pedigree).
- A family tree diagram is a model of inheritance, showing whether a characteristic was passed from parents to offspring.
- A family tree can be used to work out an individual's genotype if their phenotype and relatives' genotypes are known.
- A family tree can be used to determine the history and probability of genetic disorders: cystic fibrosis and polydactyly
Vocabulary To Learn
- family tree: A family tree diagram is a model of inheritance, showing whether a characteristic was passed from parents to offspring.
- genotype: The genotype is the combination of alleles that an individual has for each gene.
- phenotype: The phenotype is the physical characteristics of an organism.
- carrier: A carrier of a recessive genetic disorder does not express the disorder in their phenotype, but has one recessive allele in their genotype that can be passed to offspring.
- inheritance: Inheritance is the passing of genetic information from parents to offspring by reproduction.
Common Mistakes To Avoid
- The dominant allele is stronger than the recessive allele preventing its expression or that the recessive allele is an absence of the dominant allele, also that all genetic disorders are recessive.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Offspring inherit two alleles, one from each parent, the combination of these alleles is the genotype. The phenotypes of members of a family can be shown in a diagram such as a family tree (pedigree).
2. Define this scientific word and use it in context. 'family tree'
A family tree diagram is a model of inheritance, showing whether a characteristic was passed from parents to offspring. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: The dominant allele is stronger than the recessive allele preventing its expression or that the recessive allele is an absence of the dominant allele, also that all genetic disorders are recessive. Correction: Linking the allele to change in protein structure, showing that proteins are produced in the case of dominant and recessive alleles. Examples of dominant and recessive disorders provided.
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