3.7.1 Inheritance (A-level only)

what is a genotype

the genetic constitution of an organism

what is a phenotype

is the expression of this genetic constitution and its interaction with the environment.

what is an allele

the different versions of the same gene

what is a gene

a sequence of bases on the DNA molecule that codes for proteins which results in a characteristic.

what is a dominant allele and a recessive allele

A dominant allele is always expressed in the phenotype, even when there’s only one copy of it. Dominant alleles are shown by a capital letter. Recessive alleles are those with characteristics that only appear in the phenotype if two copies are present. They’re shown by lowercase letters.
Examples

what is a codominant allele

Some alleles are both expressed in the phenotype because neither one is recessive. They are said to be codominant alleles.

what is a locus

The allele of each gene is found at a fixed position, called a locus, on each chromosome in a pair.

what is a diploid organism

Humans are diploid organisms. This means we have two copies
of each chromosome — one from each parent. It’s why we have two alleles of each gene.

what is the meaning of heterozygous and homozygous

The genotype can be homozygous or heterozygous at each locus in a diploid organism. If an organism carries two copies of the same allele, it’s said to be homozygous at that locus. If an organism carries two alleles for a gene, it’s heterozygous.

diagram of a monohybrid cross

diagram of a monohybrid inheritance for codominant alleles

diagram of multiple allele crosses

diagram of dihybrid cross

diagram for cross-linkage

describe multiple alleles and epistasis

describe chi-squared test