What you'll learn
How characteristics are inherited.
Key ideas
- DNA, genes and alleles; dominant and recessive.
- Sex chromosomes (XX/XY) and simple genetic crosses.
- Genetic disorders caused by faulty alleles.
Exam tips
- Use a Punnett square for offspring ratios.
- Distinguish genotype from phenotype.
Common mistakes
- Confusing dominant and recessive.
- Muddling genotype and phenotype.