S-Cool Revision Summary

S-Cool Revision Summary

When studying genetics, the following conventions are used:

P is used as shorthand for the parent generation.

F1 is used for their offspring.

F2is used if the offspring (F1) are crossed.

Capital letters are used to denote a dominant allele.

Lower case letters are used to denote a recessive allele.

This is when neither allele is dominant.

Both alleles are expressed and contribute equally to the phenotype.

A heterozygote has an intermediate phenotype as there is partial influence from both alleles.

In this case, both alleles are dominant.

They are independent, so there is no 'blending' as in the snapdragons, instead the phenotype is a result of the full expression of both alleles.

This is where one gene affects several characteristics. For example, a disease caused by one pair of alleles may have several or many symptoms.

This is where one characteristic is affected by two or more genes (e.g, skin colour).

This is where one gene interferes with the expression of another gene.