Hereditary (Bio)

Allele

Different forms of a gene

Homozygote

Same Alleles (AA, aa)

Heterozygote

Different Alleles (Aa)

Genotype

Allele combination

Phenotype

Observable trait

Dominant expression

1 copy (allele symbol - A)

Recessive expression

2 copies (allele symbol - a)

Simple dominance

Inheritance types: AA, Aa → Dominant; aa → Recessive

Incomplete dominance

Inheritance types: Heterozygote blend (Red x White → Pink)

Co-dominance

Inheritance types: Both alleles expressed (AB)

Allele blood type =

IA, IB, i

IA &IB blood type =

Co-dominant

i blood type =

Recessive

IAIA/IAi →

A

IBIB/IBi →

B

IAIB →

AB

ii →

O

Sex-linked inheritance

Gene on X chromosome

Male

XY → 1 recessive allele shows trait

Female

XX → Needs 2 recessive alleles

Square on pedigree chart

Male

Circle on pedigree chart

Female

Shaded on pedigree chart

Affected

Half-shaded on pedigree chart

Carrier

Pedigree Charts show…

Inheritance across generations

Autosomes (non-sex)

22

Last chromosome

23rd (sex; XX & XY)