Name and explain the different modes of inheritance.

Modes of Inheritance:

- Autosomal dominant inheritance; In this mode of inheritance you only need the abnormal gene (e.g. a dominant allele) from one parent for you to inherit the disease.

- Autosomal recessive inheritance; In this mode of inheritance two copies of an abnormal gene (i.e. two recessive alleles) must be present for the disease or trait to develop.

- Sex (X/Y) linked inheritance; This mode of inheritance results from a mutant gene located on either the X or Y chromosome.  

- Mitochondrial inheritance; The inheritance of a trait encoded in the mitochondrial genome. Mitochondria have their own DNA, this mode of inheritance is always of maternal origin.