What is the impact of consanguinity on genetic inheritance?

Consanguinity increases the risk of inheriting genetic disorders due to the sharing of common ancestors.

Consanguinity, or the marriage between close relatives, can have a significant impact on genetic inheritance. This is primarily due to the increased probability of both parents carrying the same harmful recessive genes, which they have inherited from a common ancestor. When both parents carry the same recessive gene, there is a 25% chance in each pregnancy that their child will inherit the gene from both parents and develop the associated genetic disorder.

In populations where consanguinity is common, certain genetic disorders can become more prevalent. This is because harmful recessive genes can become more widespread in the gene pool of a closely related population. For example, in some Middle Eastern populations where cousin marriages are common, there is a higher incidence of genetic disorders such as thalassemia and cystic fibrosis.

However, it's important to note that not all offspring of consanguineous marriages will develop genetic disorders. The risk is increased, but it's not guaranteed. The actual risk can vary depending on the specific genes involved and other factors such as the degree of relatedness between the parents. For example, first cousins share about 12.5% of their genes, so the risk of inheriting a genetic disorder is higher than for more distantly related individuals.

Furthermore, consanguinity can also lead to a decrease in genetic diversity within a population. This can make the population more vulnerable to certain diseases or environmental changes, as there is less variation in the genes that could potentially provide resistance.

In conclusion, while consanguinity can increase the risk of inheriting genetic disorders, it's not a guarantee. The actual risk can vary greatly depending on a variety of factors. Nonetheless, it's an important factor to consider in genetic counselling and public health planning, particularly in populations where consanguineous marriages are common.