Genetic Diagrams (Edexcel GCSE Biology): Revision Notes

Genetic Diagrams

Genetic Diagrams

The inheritance of a characteristic is called monohybrid inheritance (inheritance from one trait)

You can use a monohybrid cross to show how recessive and dominant traits for a single characteristic are inherited

The outcome expressed as a:

• Probability
• Ratio
• %

Family pedigrees

A pedigree is a diagram that shows a family history for inheritance of a genetic condition or of certain genes

Example- cystic fibrosis (genetic disorder of cell membranes):

• The allele which causes cystic fibrosis is a recessive allele 'f' carried out by 1 in 30 people
• As its recessive people with one copy wont carry disorder so both parents must have the disorder or be carriers Horizontal lines- link parents to each other

Vertical lines- link to children

What it shows:

• There is a 1 in 4 chance (25%) that a baby will have cystic fibrosis and 1 in 2 chance (50%) that it will be a carrier
• FF- Affected
• Ff- carrier
• ff- have the disorder