Biology Genetics lesson Vocab

Edexcel A level biology

Gene

Gene

A sequence of DNA bases that code for a polypeptide chain

Genome

All DNA bases that code for all the proteins in an organism

Triplet code

3 bases code for one amino acid (ex: AAA codes for lysine)

Degenerate code

Different triplets can code for the same amino acid to minimize the effects of mutants (ex: AAA and AAC both code for lysine)

Non-overlapping code

Each base is used once in a triplet (ex: AAC and GAG both give 2 distinct codes)

Universal code

The same triplet for the same amino acids, in all organisms (ex: AUG codes for methionine)

Allele

A variation of a gene (ex: T is the allele for tall and t is the allele for short)

Homozygous alleles

both alleles for a gene are the same (ex: TT [tall] and tt [short])

Heterozygous alleles

Both alleles for a gene are different (ex: Tt [tall])

Dominant allele

Only one allele is needed to be expressed in the phenotype

Recessive allele

both alleles are needed to be expressed

Genotype

All the alleles of an organism (‘the genetic makeup of an organism’ is NOT an accepted definition)

Phenotype

The outward characteristics of an organism. It is determined by both the genotype and the environment