Gene

From ArticleWorld

The units of heredity in living organisms are known as genes. Genes are found in the genetic material of organisms. They control the physical features of an organism as well as the behavior of organisms to an extent. Genes are passed from parents to offspring during reproduction and can also be passed through viruses between unrelated individuals. Genes are necessary to protein synthesis in organisms.

Properties and types

Genes play an instrumental role in protein synthesis. They determine how the DNA sequence is converted into a protein sequence. The genes, through the proteins they encode, control development of organisms from fertilization and as well as in day to day function of cells, organs and tissues. The proteins they produce are important for structural roles and in the manufacture and regulation of other molecules. Genes in existence today are the genes that have been successfully reproduced from generation to generation. Genes do not necessarily become extinct when an individual dies as most genes tend to shared with other organisms.

Errors may occur in the sequence of genes due to errors in DNA sequencing. If this is passed along to the next generation variations can arise in species. Variants of a single gene are termed alleles. Allele differences can cause a change in physical appearance. Common alleles are called the wild type allele and uncommon alleles are known as mutants.

Chemistry

There are four types of nucleotides that compose DNA. A string of three of these nucleotides is called a codon. Codons sequences in genes determine the amino acid order of the protein. In eukaryotes, genes are separated by non-coding sequences. These are called introns. Introns are removed before transcription by splicing. All the genes as well as the intervening DNA make up the genome. The genome is divided among the chromosomes. Genes that appear together on a chromosome in one species may be found in separate chromosomes in other species.