Gene

:For the band called Gene, see Gene (band)

Overview

Properties of genes

In molecular biology, the DNA of a gene encodes the chemical structure of a protein. The genetic code determines the sequence of the amino acids that make up a protein. The coding of a three nucleotide DNA sequence to a specific amino acid is essentially the same for all known life, from bacteria to humans.

Related Topics:
Molecular biology - Protein - Genetic code - Nucleotide - Life - Bacteria - Humans

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Through the proteins they encode, genes govern the cells in which they reside. In multicellular organisms they control the development of the individual from the fertilized egg and the day-to-day functions of the cells that make up tissues and organs. The instrumental roles of their protein products range from mechanical support of the cell structure to the transportation and manufacture of other molecules and to the regulation of other proteins' activities.

Related Topics:
Organisms - Development - Fertilized - Egg - Tissue - Organ

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The genes that exist today are those that have reproduced successfully in the past. Often, many individual organisms share a gene; thus, the death of an individual need not mean the extinction of the gene. Indeed, if the sacrifice of one individual enhances the survivability of other individuals with the same gene, the death of an individual may enhance the overall survival of the gene. This is the basis of the selfish gene view, popularized by Richard Dawkins. He points out in his book, The Selfish Gene, that to be successful genes need have no other "purpose" than to propagate themselves, even at the expense of their host organism's welfare. A human that behaved in such a way would be described as "selfish," although ironically a selfish gene may promote altruistic behaviors. According to Dawkins, the possibly disappointing answer to the question "what is the meaning of life?" may be "the survival and perpetuation of ribonucleic acids and their associated proteins".

Related Topics:
Richard Dawkins - The Selfish Gene - Propagate themselves - Altruistic

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Types of genes

Due to rare, spontaneous errors (e.g. in DNA replication) mutations in the sequence of a gene may arise. Once propagated to the next generation, this mutation may lead to variations within a species' population. Variants of a single gene are known as alleles, and differences in alleles may give rise to differences in traits, for example eye color. A gene's most common allele is called the wild type allele, and rare alleles are called mutants.

Related Topics:
DNA replication - Mutation - Allele - Wild type - Mutant

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Normally, RNA is an intermediate product in the translation of a molecular gene into a protein. However, for some gene sequences, RNA molecules are actually the functional end products. For example, RNAs known as ribozymes are capable of enzymatic function, or small interfering RNAs have a regulatory role. The DNA sequences from which such RNAs are transcribed are known as non-coding RNA, or RNA genes.

Related Topics:
RNA - Ribozymes - Enzymatic function - Small interfering RNAs - Non-coding RNA - RNA gene

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All living organisms carry their genes and transmit them to offspring as DNA, but some viruses carry only RNA. Because they use RNA, their cellular hosts may synthesize their proteins as soon as they are infected and without the delay in waiting for transcription. On the other hand, RNA retroviruses, such as AIDS, require the reverse transcription of their genome from RNA into DNA before their proteins can be synthesized.

Related Topics:
Virus - Retrovirus - AIDS - Reverse transcription

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Human gene nomenclature

For each known human gene the HUGO Gene Nomenclature Committee (HGNC) approve a gene name and symbol (short-form abbreviation). All approved symbols are stored in Genew, the Human Gene Nomenclature Database. Each symbol is unique and each gene is only given one approved gene symbol. It is necessary to provide a unique symbol for each gene so that people can talk about them. This also facilitates electronic data retrieval from publications. In preference each symbol maintains parallel construction in different members of a gene family and can also be used in other species, especially the mouse.

Related Topics:
HUGO - Nomenclature - HGNC - Symbol - Abbreviation - Database - Electronic - Data - Construction - Gene family - Species - Mouse

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Typical numbers of genes in an organism

The following table gives typical numbers of genes and genome size for some organisms. Estimates of the number of genes in an organism are somewhat controversial, because it is only possible to discover a gene, and no techniques currently exist to prove that a DNA sequence contains no gene. Nonetheless, estimates are made based on current knowledge.

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