Summary
Genetics studies how traits pass from parents to children: eye colour, the shape of a seed… The information is in DNA, a molecule found in the nucleus of cells and organised into chromosomes. Each piece of DNA that carries the instruction for a trait is a gene.
Each trait comes from two versions of the gene, the alleles: one from the father and one from the mother. An allele can be dominant, showing up even with just one copy, or recessive, seen only when both are present. Gregor Mendel discovered these rules in the 19th century by crossing pea plants, and today results are predicted with the Punnett square. A change in the DNA is called a mutation, and some are inherited.
Key points
- Genetics studies how traits are inherited from parents to children.
- The information is in DNA, inside the nucleus, organised into chromosomes.
- A gene is the piece of DNA with the instruction for a trait.
- Each trait has two alleles, one from each parent.
- Dominant allele (shows with one) versus recessive (needs both).
- Mendel set out the laws of inheritance by crossing pea plants.
- The Punnett square predicts the ratios of the offspring.