5. Alleles and gene expression

what is a gene locus

the position of a gene on a chromosome

• all alleles of the same gene are found in the same gene locus homologous chromosomes

what is a Allele

one particular variant of a gene received from a parent

• diploid organisms have 2 alleles for every gene

what is a Dominant allele

an allele that is more dominant than the 2nd

• represented by capital lettre

what is a recessive allele

the 2nd allele that is dominated by the dominant allele

• represented by a lower lettre

what is a genotype

Both alleles present for a particular gene (TT,Tt,tt)

what is a homozygous genotype

genotype with the same alleles (TT,tt)

what is a heterozygous genotype

has 2 different alleles (Tt)

Phenotype

the physical characteristics expressed by the genotype (short, tall, eye colour)

Heredity

trait that is passed down from parent to offspring

P (parent) generation

the 2 individuals that are bred together

F (filial) generation

the offspring produced

Monohybrid

a cross in which one one trait is observed

Punnett square

a chart used to show possible combinations of alleles in offspring