Genetics Biology Aqa Unit 4 A2

Front 1

Genotype

Back 1

The alleles coding for a particular feature determining the potential characteristic.

Front 2

Mutation

Back 2

Change to DNA (inherited if in gametes).

Front 3

Phenotype

Back 3

Observable feature as a result of the genotype and environment.

Front 4

Gene

Back 4

Section of DNA, sequences of nucleotide bases determining a feature. It codes for an enzyme leading to a feature.

Front 5

Allele

Back 5

Variation of a gene.

Front 6

Locus

Back 6

Position of an allele on a chromosome.

Front 7

Homologous Chromosome

Back 7

chromosomes occurring in pairs in which alleles occur on the same locus on both chromosome.

Front 8

Homozygous

Back 8

The same alleles for a feature.

Front 9

Heterozygous

Back 9

The alleles for a feature are different.

Front 10

Dominant

Back 10

Always expressed when present, even if another allele is present.

Front 11

Recessive

Back 11

Only expressed when heterozygous, otherwise it is overruled by dominant allele.

Front 12

Homozygous Dominant

Back 12

2 dominant alleles.

Front 13

Homozygous Recessive

Back 13

2 recessive alleles.

Front 14

Co-dominant

Back 14

Both alleles are as dominant as each other and so are both expressed e.g. AB blood group.

Front 15

Multiple Alleles

Back 15

More than 2 alleles for a feature are possible but only two can ever be present in an organism.

Front 16

Gamete

Back 16

Sex cell in which only one allele of a pair is present.