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There are two types of molecular genes: protein-coding genes and non-coding genes. [1] [2] [3] During gene expression (the synthesis of RNA or protein from a gene), DNA is first copied into RNA. RNA can be directly functional or be the intermediate template for the synthesis of a protein.
However, the proposed connection between a single gene and a single protein enzyme outlived the protein theory of gene structure. In a 1948 paper, Norman Horowitz named the concept the "one gene–one enzyme hypothesis". [2] Although influential, the one gene–one enzyme hypothesis was not unchallenged.
If the sequence of the nucleotides in a gene changes, the sequence of the amino acids in the protein it produces may also change—if part of a gene is deleted, the protein produced is shorter and may not work anymore. [6] This is the reason why different alleles of a gene can have different effects on an organism.
A second version of the central dogma is popular but incorrect. This is the simplistic DNA → RNA → protein pathway published by James Watson in the first edition of The Molecular Biology of the Gene (1965). Watson's version differs from Crick's because Watson describes a two-step (DNA → RNA and RNA → protein) process as the central ...
A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. [1] Activators are considered to have positive control over gene expression, as they function to promote gene transcription and, in some cases, are required for the transcription of genes to occur.
Alternative splicing produces three protein isoforms.Protein A includes all of the exons, whereas Proteins B and C result from exon skipping.. Alternative splicing, alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to produce different splice variants.
Hox proteins are a subset of transcription factors, which are proteins that are capable of binding to specific nucleotide sequences on DNA called enhancers through which they either activate or repress hundreds of other genes. The same Hox protein can act as a repressor at one gene and an activator at another.
A regulator gene may encode a protein, or it may work at the level of RNA, as in the case of genes encoding microRNAs. An example of a regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase). [1]