Summary Inheritance A level Biology AQA

Inheritance summary notes
08 February 2023 14:58




Definitions:

• Haploid = 1 copy of chromosomes (half the number that are in a diploid cell)

• Diploid = 2 copies of each chromosome

• Genotype = genetic constitution of an organism - the alleles an organism has

• Phenotype = the expression of the genotype and its interaction with the environment

• Allele = variations of the same gene (due to differences in base sequences)

• Gene = a section of DNA on a chromosome that codes for a polypeptide, tRNA or rRNA

• Locus = the position on a chromosome where a particular gene is found

• Homologous chromosomes = chromosomes in a pair, one parental and one maternal,
with same genes at same loci but could have different alleles

• Homozygous = alleles of a particular gene are identical

• Heterozygous = alleles of particular gene are different

• Dominant Allele = allele that is always expressed in the phenotype even if only one is
present

• Recessive Allele = effect of the allele is only apparent in the phenotype in the presenc
another recessive allele

• Codominant alleles = condition in which both alleles for one gene in a heterozygous
organism contribute to the phenotype




Pure-breeding- breeding repeatedly with each other so that one characteristic is bred

Basic law of genetics- in diploid organisms, characteristics are determined by alleles that occ