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Recessive gene

Biology  Recessive  Reciprocal cross

Recessive gene: A gene which must b e present on both chromosomes in a pair to show outward signs of a certain characteristic.
Recombinant DNA: A form of DNA produced by splicing together segments of DNA from two or more organisms.


Recessive gene. Characterized as having a phenotype expressed only when both copies of the gene are mutated or missing.

Recessive gene
A gene which will be expressed only if there are 2 identical copies or, for a male, if one copy is present on the X chromosome.
Reciprocal translocation ...

recessive gene Gene that is masked by its dominant allelic partner, having the recessive phenotype expressed only when both alleles for a given trait are recessive.

So, recessive genes do not tend to be lost from a population no matter how small their representation.

PKU is a recessive genetic disease in which the person does not have the ability to break down the amino acid phenylalanine. The level of phenylalanine in the persons blood builds up and interferes with the development of the nervous system.

(See Dominant gene, Fusion gene, Gene amplification, Gene expression, Gene flow, Gene pool, Gene splicing, Gene translocation, Recessive gene, Regulatory gene.) Gene amplification. The presence of multiple genes.

Carrier -- an individual heterozygous for a single recessive gene. cDNA -- complementary DNA produced from a RNA template by the action of RNA- dependent DNA polymerase.

Carrier (heterozygote) An individual who carries one copy of a recessive gene.
cDNA See complementary DNA.
Cell The basic structural unit of all living organisms.

Autosomal recessive disorders occur in individuals who are homozygous for a particular recessive gene mutation. This means that they carry two copies (alleles) of the same gene.

Parent 2 possesses 2 recessive genes in its genotype
The gametes produced by parent 1 all contain the dominant gene while parent 2's gametes all possess the recessive gene.
When parent 1 and 2's gametes are crossed, the genotype is Rr.

Where an individual receives one albinism gene and one normal gene, that person will not show outward signs of the condition, but will become a carrier of the recessive gene.

Term coined by Voigt (1926) for the percentage with which a dominant or homozygous recessive gene expresses itself in the phenotype. Qualitative concept of gene expression. It depends both on genotype and environment.

NB: in a problem, or experiment, some conventions are used for writing and labelling dominant and recessive gene. The dominant gene has a capital letter and the recessive is named with the same letter in lower case. e.g.

hemophilia A human sex-linked recessive genetic disorder that results in the absence of certain blood-clotting factors, usually Factor VII. Hemophiliacs suffer from an inability to clot their blood.

cystic fibrosis An autosomal recessive genetic disorder that causes the production of mucus that clogs the airways of the lungs and the ducts of the pancreas and other secretory glands.

If a gene is carried on the Y chromosome, only men can inherit it. Recessive genes carried on the X chromosome are always expressed for men, who only have one X chromosome, but must be homozygous to be expressed in women.

Close relatives are likely to carry similar genes and gene defects, and are therefore more likely to bear children with recessive genetic diseases if they mate.

Likewise, there are some genetic algorithm implementations that do have diploid chromosomes and dominant and recessive genes (Goldberg 1989, p.150; Mitchell 1996, p.22).

Scientists write gene pairs by using capital and lowercase letters. (TT, Tt, tt) The capital letter represents a dominate gene, while the lower case letter indicates a recessive gene.

If the alleles are different, the dominant allele will be expressed, while the effect of the other allele, called recessive, is masked. In the case of a recessive genetic disorder, ...

In this case, the genetic disorder is known as a hereditary disease. This can often happen unxpectedly when two healthy carriers of a defective recessive gene reproduce, but can also happen when the defective gene is dominant.

Both parents carry the recessive gene for the syndrome and have a risk of 25% of having an affected child. The probability of them having three affected children was 1/4 X 1/4 X 1/4 = 1/64. They had unusually bad luck.

See also: See also: Recessive, Gene, Organ, Dominant, Trait

Biology  Recessive  Reciprocal cross

 
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