Gene Mutation

The nature of Gene

The genetic material of most organisms, DNA is a double-stranded helix comprising a long chain of nucleotide bases with a sugar phosphate backbone.

During mitotic cell division, chromosomal replication produces two daughter cells, each of which contains identical DNA, assuring the stability of the heredity material.

Gene of DNA in eukaryotic organisms (RNA insome viruses) control phenotype by coding for the structure of proteins, which are the main structural and catalytic molecules in an organism. During protein synthesis, the order of the nucleotide pairs in DNA dictates the corresponding order of amino acids that give proteins their specific shape and function.

In humans the DNA in each cell contains about 3 billion base pairs, distributed among 22 sets of autosomal chromosomes and one set of chromosomes in the nucleus as well as one set of chromosomes in each mitochondrion. Only about 2 percent of a person's DNA forms the actual genes, as well, the rest constitutes either noncoding "spacer" regions between genes or noncoding "intron" regions within genes.

Gen Mutation

Mutation is the process by which genes changes from one form to another. Mutations may be caused by such mutagen as X rays, ultraviolet rays, nitrious acid, ethyl methane sulfonate, and nitrosoguanidine; less frequently, mutation may occur spontaneously as a result of accidental changes in the chemistry of the cell. Because mutation is random, haphazard change, most mutants contain damaged genes that are nonfunctional. Mutant usually do not live long in nature.

A mutation in DNA usually result in an altered nucleotide sequence, either by substitution, addition, deletion, or insertion, which is translated into an altered amino acid sequence that usually produces a change in normal body function.

All human carry quite a large number of deterious and lethal mutant genes that are recessive. Each mating is a kind of lottery, in which the offspring reveal whether or not the parents mutations are at identical loci. For example if both parents are heterozygous (Aa) for a gene pair in which the recessive allele is deleterious, then 1/4 of their children will show genetic diseases of the kind controlled by that locus.