inheritance patterns

Pedigree chart

Mendelian inheritance patterns

• Autosomal dominant

• autosomal recessive

• y-linked very rare)

• X-linked dominant

• x-linked recessive

• matrilineal inheritance

Rules to remember

1. Dominant condition 50% chance

2. Recessive conditions 25% chance

3. Carrier status - recessive?

4. No male-or-male transmission in X-linked disease

Autosomal dominant

Only one copy needed to express disease

Both sexes are affected and may transmit the gene to offspring of either sex

Aa x aa = 50% chance of cold having it

Autosomal recessive

Two mutant alleles required

Person affected can be of either sex and both with unaffected parents (heterozygotes = asymptomatic carriers)

Cold of carrier parents has 25% chance of getting it

X-linked inheritance dominant

Affected individuals can be of either sex and at least one parent is affected

More females than males affected (but females have more mild symptoms)

If mother has condition: 50% of boys will have it , 50% off girls will have it

If father has condition ask his daughters will have it

X-linked recessive inheritance

25% chance of children having it; usually males born to asymptomatic carrier mother

passed by mother, no male-to-male inheritance

Matrilineal inheritance

Individuals can be of either sex but affected makes do not transmit the condition to any of their children

If mother has it all her children will