Inheritance (patterns)
Autosomal dominant conditions:-
Autosomal recessive conditions:-
X-linked dominant conditions:-
X-linked recessive conditions:-
Y-linked conditions:-
Mitochondrial inheritance:-
- All forms of transmission observed (male to male, male to female, female to female)
- Transmitted from one generation to the next (vertical transmission)
- Males and female affected in equal proportions
- Parents usually one affected heterozygote and one unaffected homozygote
- If only one parent affected there is a 50% chance that a child will inherit the mutated gene
Autosomal recessive conditions:-
- Males and female affected in equal proportions
- Two copies of the gene must be mutated for a person to be affected
- both parents' usually unaffected heterozygotes
- Two unaffected people who each carry one copy of the mutated gene have a 25% chance with each pregnancy of having a child affected by the disorder
X-linked dominant conditions:-
- Males and females are both affected in these disorders, with males typically being more severely affected than females
- The sons of a man with an X-linked dominant disorder will all be unaffected
- A woman with an X-linked dominant disorder has a 50% chance of having an affected foetus
X-linked recessive conditions:-
- Males are more frequently affected than females
- Transmitted through carrier females to their sons (knights move pattern)
- Affected males cannot pass the condition onto their sons
- A woman who is a carrier of an X-linked recessive disorder has a 50% chance of having sons who are affected and a 50% chance of having daughters who are carriers
Y-linked conditions:-
- Every son of an affected father will be affected
- Female offspring of affected fathers are never affected
Mitochondrial inheritance:-
- Mitochondria are inherited only in the maternal ova and not in sperm
- Males and females affected, but always being maternally inherited
- An affected male does not pass on his mitochondria to his children, so all his children will be unaffected
