Inbreeding
In breeding is sexual reproduction between relatives. The practice
reduces the number of different genes the couple can pass to their children,
since the couple may have inherited some of the same genes from their common
relatives. So the practice reduces genetic diversity in the population.
Besides decreasing diversity in the gene pool, the practice increases the
chances that the child of such a union will inherit a defective gene. (Defective genes usually occur randomly as a result of a
mutation). Each of us has about ten gene pairs (out of a total of many
thousands of genes) for which one copy of each pair is defective. Since
defective genes occur randomly, it's unlikely we will share common defective
genes with anyone but a relative. Having a child with a relative,
though, ups the chances the child will inherit a defective gene.
Children inherit two copies of all genes. One defective gene copy may
not cause a defect. It may remain hidden as a recessive gene.
Inbreeding also increases the chances for the child to inherit two
copies of a defective gene. That's real trouble. Then the inherited
defective gene pair will not do what it's supposed to do and the child will end
up with a defect --- perhaps a subtle one or perhaps profound.
For example, suppose a brother and a sister have each inherited one good copy
and one defective copy of a particular gene type. If the siblings have a child
together, then the child has a 50% chance of getting the defective gene from
each parent. If the baby does inherit both defective copies, the baby
will develop a defect.
Consequently, first-generation inbred individuals are more likely to show
such physical and health defects as:
- Reduced fertility and sperm viability
- Increased genetic disorders
- Lower birth rate
- Higher infant mortality
- Loss of immune system function
(Answered 25 July 2009)
Return to
Space
Colonization
Comment
|
