Home (Recessive gene)

 Biology 

What is what? Everything you always wanted to know.
  » »
 
   

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
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.
So long as certain conditions are met (to be discussed next), gene frequencies and genotype ratios in a randomly-breeding population remain constant from generation to generation.

Examples of recessive genetic diseases are: cystic fibrosis, albinism, phenylketonuria, galactosemia, Tay-Sachs disease.
16. What are some diseases or genetic abnormalities caused by dominant genes? Why are severe dominant genetic diseases rarer than recessive ones?

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

Carrier -- an individual heterozygous for a single ~. 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 ~.
cDNA See complementary DNA.
Cell The basic structural unit of all living organisms. A human cell is made up a central nucleus (containing DNA) a cytoplasm and a outer cell membrane.

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

Parent 2 possesses 2 ~s in its genotype
The gametes produced by parent 1 all contain the dominant gene while parent 2's gametes all possess the ~.
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 ~.

Term coined by Voigt (1926) for the percentage with which a dominant or homozygous ~ expresses itself in the phenotype. Qualitative concept of gene expression. It depends both on genotype and environment.
If all individuals of the genotype show the trait, penetrance is 100%.

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

cystic fibrosis An autosomal ~tic disorder that causes the production of mucus that clogs the airways of the lungs and the ducts of the pancreas and other secretory glands.
cytokinesis The division of the cytoplasm during cell division.

Sex linked genes are carried on the X and Y chromosomes, also known as the sex chromosomes. If a gene is carried on the Y chromosome, only men can inherit it. ~s carried on the X chromosome are always expressed for men, who only have one X chromosome, ...

Close relatives are likely to carry similar genes and gene defects, and are therefore more likely to bear children with ~tic diseases if they mate. Because of this, a prohibition against marriage of close relatives is found in virtually every culture in the world.

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

Koike-Yusa H, Li Y, Tan E-P, Velasco-Herrera MDC, Yusa K: Genome-wide ~tic screening in mammalian cells with a lentiviral CRISPR-guide RNA library. ...

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 ~.

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 ~tic disorder, an individual must inherit two copies of the mutated allele in order for the disease to be present.

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

Both parents carry the ~ 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: What is the meaning of Recessive, Gene, Organ, Dominant, Human?

◄ Recessive   Reciprocal cross ►
 
RSS Mobile