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A gene is a unit of | A gene is a hereditary unit consisting of [[DNA|DNA]] made up of [[Nucleotide|nucleotides]], complementary to each other on opposite sides of the DNA molecule, occupying a specific position (loci) on a [[Chromosome|chromosome]] that specifies for a specific characteristic within an organism<ref>The American Heritage® Dictionary of the English Language, Fourth Edition,2000(Updated in 2009) Published by Houghton Mifflin Company.</ref>. Genes are transcribed into [[MRNA|mRNA]] within the cell [[Nucleus|nucleus]] and then [[Transcription|translated]] to create a [[Polypeptide|polypeptide]] chain of a specific sequence that go on to form a specific [[Protein|protein]]. [[Allele|Alleles]] are different forms of a gene, and are present in a diploid cell on both of the [[Homologous chromosome|homologous chromosomes]] at the exact same loci. They are variants because of [[Mutation|mutations]]; random [[Nitrogenous base|nitrogenous base]] sequence changes that lead to different nucleotide sequences. A different base sequence can therefore code for a different [[Codon|codon]] on the mRNA transcribing molecule, and therefore lead to the binding of a different [[Anticodon|anticodon]] on a [[TRNA|tRNA]] molecule, producing an alternate sequence of [[Amino acid|amino acids]] during the process of translation on the [[Ribosome|ribosome]]. This alternate sequence of amino acids may produce a different protein to the non-mutated form of the gene. In this way, genes are vital coding units for the proteins of the cell<ref>Bruce Alberts et al.(2002)'Molecular Biology of the Cell' -- 4th ed. New York, Garland Science</ref>. | ||
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Latest revision as of 12:15, 16 November 2018
A gene is a hereditary unit consisting of DNA made up of nucleotides, complementary to each other on opposite sides of the DNA molecule, occupying a specific position (loci) on a chromosome that specifies for a specific characteristic within an organism[1]. Genes are transcribed into mRNA within the cell nucleus and then translated to create a polypeptide chain of a specific sequence that go on to form a specific protein. Alleles are different forms of a gene, and are present in a diploid cell on both of the homologous chromosomes at the exact same loci. They are variants because of mutations; random nitrogenous base sequence changes that lead to different nucleotide sequences. A different base sequence can therefore code for a different codon on the mRNA transcribing molecule, and therefore lead to the binding of a different anticodon on a tRNA molecule, producing an alternate sequence of amino acids during the process of translation on the ribosome. This alternate sequence of amino acids may produce a different protein to the non-mutated form of the gene. In this way, genes are vital coding units for the proteins of the cell[2].