Pamela inherited Sickle Cell Anaemia from both her mum and dad
With a few exceptions, we all inherit two versions of each of our
genes (known as ‘alleles’), one from each parent.
The role that each gene pair plays in our bodies is the same, but
tiny differences in the code of their DNA result in subtle differences.
For example, we inherit a gene for eye colour from both our parents.
But we might inherit the version for blue eyes from our mother and the
version for brown eyes from our father.
But why doesn't this make our eyes browny-blue? It's because the
allele for blue eyes is ‘recessive’ to the gene for brown eyes.
If you receive one gene for each colour you'll have brown eyes
because the effects of the blue-eyed gene are masked by that of the
brown-eyed one.
Recessive disorders
Recessive inheritance
Photo: US Nat. Library of Medicine
There are around 4,000 known inherited conditions that are caused by a
difference in a single gene and the majority of these follow a
recessive pattern of inheritance.
The most common life-limiting inherited genetic disorder in the UK is Cystic Fibrosis. It affects the internal organs, especially the lungs and
digestive system, by clogging them with thick, sticky mucus.
Around 1 in 25 people are carriers of the gene which causes Cystic Fibrosis. The gene is on chromosome seven and controls the way the
body's cells handle sodium.
Carriers don't have any symptoms because they received one of these altered genes from one parent and a healthy copy of the same gene from
the other parent. Because Cystic Fibrosis is a recessive condition, the healthy copy
'cancels out' the effects of the altered one.
1 in 2,500 babies are born with Cystic Fibrosis in the UK each year which equates to around five
babies born each week. They inherited two copies of the altered gene.