Tuesday, 20 November 2012

Explanation of Hemochromatosis Genetics

What is the difference between homozygous and heterozygous?

Humans contain two copies of each gene, one from the father and one from the mother. If a mutation occurs in just one copy of the gene then that individual is considered heterozygous. On the other hand if both copies of a gene are mutated then that individual is homozygous genotype.

Majority of hereditary disorders are harmful if both copies of a gene are affected, which means protein products from both genes may fail to operate properly
In heterozygous genotypes one copy of the gene is healthy and can produce fine proteins thus these individuals are usually not affected and are considered just carriers. However in a few hereditary disorders heterozygous individuals may suffer from a milder version of the disease.
Homozygous vs Heterozygous
If we assign a letter such as B to a dominant genetic or hereditary trait then b will be a defective part:
If homozygous genotypes are represented by BB (normal) and bb (affected) and heterozygous genotypes are represented by Bb (carrier genotype)
Below are examples and probabilities of children born to parents with different genotypes:
The Parents **** BB x BB **** Presents Two healthy parents
Their Children**** 100% BB**** Presents All children will be normal

The Parents BB x Bb – Presents One healthy and one carrier parent
Their Children 50% BB - 50% Bb Presents Children could be half normal and half carrier

The Parents Bb x Bb - Two carrier parents
Their Children 25% BB, 50% Bb, 25%bb – Presents 25% of children could be normal, half carrier, and another 25% could be affected (mutant)
The Parents ***BB x bb*** One healthy and one affected parent
Their Children*** 100% Bb*** All children will be carriers

The Parents ***bb x bb ***Two affected parents
Their Children***100% bb ***All children will be affected mutants

Below is a diagram which may make it clearer

1 comment:

  1. I am a carrier. I have 1 gene. I do have to have phlebomies but not as often as those with 2 genes. My question is, what is a high ferritin level and hemicrit? My doctor say's he wants to keep me at 45 or little below.