Recessive allele

A recessive allele is a strain of genetic code that does not create a phenotype if a dominant allele. In a dominant/recessive relationship between two alleles, the effects of the recessive allele are masked by the more dramatic effects of the dominant allele. An allele is a specific variation of a gene or specific segment of DNA. Different alleles produce slightly different proteins, which function in different ways.

In dominant/recessive relationships, the recessive allele produces a non-functional protein. The dominant allele produces a functional protein. An individual heterozygous will have the same appearance as a homozygous dominant individual. This means that a organism with two dominant alleles looks the same as an organism with a single functional allele. Many enzymes can process their substrates so fast that one functional allele can produce enough enzyme to meet the needs of the organism. Most enzymes are regulated anyway through a variety of methods and are not allowed to convert the enzyme to a functional allele. substrate to its full potential.

A common misconception is that a recessive allele is somehow worse, evolutionarily, than a dominant allele. The natural selection can select for a recessive allele if the products of a dominant allele are unfavourable in the environment in which a population. While genes only code for proteins, these proteins interact in ways that build and create the entire structure of an organism. Sometimes, not having a functioning enzyme is more beneficial than having one.

Examples of recessive allele

Coat colour

In many fur-bearing animals, coat colour is determined in part by a gene that controls melanin production. Melanin is an important pigment that colours the hair black or brown, depending on its concentration. The gene partly responsible for melanin production produces the enzyme that converts the melanin from a molecule intermediate molecule into a functional pigment molecule. The recessive allele for melanin production produces an enzyme that does not function to convert the intermediate molecule.

Suppose a population of black rabbits is set adrift in a small boat. The boat crashes on a cold island, covered almost all year round with snow. There are only a few predators on the island, so they cannot eat all the rabbits at once. Now suppose that two black rabbits, both heterozygous for the melanin gene, start breeding. According to a Punnett’s tableIn this case, a homozygous recessive individual will be created between the parents at least 25% of the time. These individuals will not be able to produce melanin and will be white. In this generation, black rabbits eat much more than white rabbits. As such, the white rabbits have a better chance of reproducing.

If they produce successful offspring, the white recessive allele will increase in frequency in the population. Eventually, the predator will eat all or most of the black rabbits. Although the black allele will decrease in frequency, it will remain the dominant allele. This means that only one black allele will be needed to produce a black phenotype, although the total number of black alleles in the population will decrease dramatically.

Tay-Sachs disease

Tay-Sachs disease is a recessive disorder, caused by non-functional alleles in the gene HEXA. The gene encodes several lysosomal enzymes. The enzymes it encodes, beta-N-acetylhexosaminidase A and others, are responsible for the breakdown of certain lipids. If these lipids cannot be broken down, they rapidly accumulate in the brain and interfere with many processes. Mutations that cause Tay-Sachs can arise in several areas of the gene and create enzymes with different functionalities.

People with Tay-Sachs disease experience different periods of symptom onset, as a result of the complex action of recessive alleles. Recessive alleles caused by different mutations produce enzymes that vary in their level of function. Although two recessive alleles mean that you will get the disease, it is still a mystery when the disease will strike. Heterozygous individuals show no symptoms of disease, because one functional enzyme is sufficient to remove excess lipids from cells. Because only one dominant allele is needed to produce a functional phenotype, Tay-Sachs is considered a recessive disorder.

• Dominant: an allele with the ability to hide the effects of a non-dominant allele.
• Heterozygous: individual with two alleles of different types.
• Allele frequencyThe number of a certain type of allele, divided by the total number of alleles in a population.
• Natural selectionprocess by which allele frequencies in populations are modified in response to the environment.

It also discovers the dominant allele.