Effect of Recessive Genes
Name: Sarah M.
I tried to check your archive of questions first but the
webpage was unavailable.
I need to know exactly what the effect of a recessive gene is? I
understand what a recessive gene is but am finding its effects hard to get
my head around
Genes simplistically do there work by making a protein...each gene has a
double copy one from the mom one from the dad...If the protein from the mom
is more effective at doing its job ...its dominant if the one from the dad
is less effective its recessive...so brown eyes is (mostly) because the gene
to produce pigment (brown) will mask the gene to produce much less pigment
(ending in blue) . blue is recessive to brown because when both genes are
present in the same individual the blue doe not show...the showing is called
phenotype...what the genes are is called phenotype so a blue and brown eye
compliment of genes in one person will be a genotype of a mix of the two
genes one which produces little pigment the other producing enough to
generate the brown eye color so the phenotype will be brown (what we see).
The person's phenotype, if they are blue eyed, automatically reveals their
genotype blue eyes is only seen with both recessive genes that produce
Peter Faletra Ph.D.
Office of Science
Department of Energy
The effect of a recessive gene depends on the trait. Remember that DNA codes
for traits and contains the instructions for making proteins. Proteins have
many functions in the body-structural, hormones, other messenger type
molecules, etc. A recessive trait may code for a protein that is either less
functional or perhaps non-functional. Take the case of a structural protein.
Let's say the dominant form codes for a fully functional product and the
recessive form doesn't allow for the proper structure to be maintained.
Let's also say that there is enough protein made by one gene so that if the
person is heterozygous (has one functional and one non-functional copy) the
structure can still be maintained. Only if there are two copies of the
recessive gene is there a problem. In the case of sickle cell trait, if a
person is homozygous dominant, they make only normal hemoglobin. If the
person is heterozygous, they have a mixture of normal hemoglobin and sickle
hemoglobin in their blood, but there is enough normal hemoglobin to get by.
If the person is recessive, they have only sickle cell hemoglobin and can
have problems. It depends on the trait and what the gene codes for as to the
effect of the recessive trait.
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Update: June 2012