Cellular control GapFill

Not all of the genome consists of  proteinsgeneschromatidsnuclei, which code for the amino acid sequence of a polypeptide or a functional RNA; some of the genetic information found in eukaryotes does not have a direct coding purpose. Within genes, these sections are known as  intronsanticodonsoutronsexons, while the coding sections are exons.

During eukaryotic  translationtranscriptionmeiosismitosis, DNA strands separate and act as templates for the formation of complementary  allelemDNAprimary mRNAtRNA molecules. The enzyme  hydrolaseRNA polymerasephosphorylaseRNA helicase facilitates this process by binding to  an operatoran activatora repressora promoter region and joining adjacent nucleotides together in the new strand. The molecule is then spliced to remove the non-coding segments, creating a  secondary mRNAribosomal RNApost-mRNAmature mRNA molecule.

Gene mutations may arise spontaneously or as a result of a fault during DNA replication. They are changes to one or more  monosaccharidesphosphatesamino acidsnucleotides in a sequence. Some changes can render a resulting polypeptide non-functional and have huge effects on an organism's phenotype - for example, a single base  replacementinversiondeletionphosphorylation near the start of a sequence can cause a frameshift, so that all the downstream triplets change. If the wrong base is incorporated into a sequence it is known as a  base conversionbase miscalculationbase exchangebase substitution; however, because many amino acids are coded for by more than one triplet, this does not always result in a change in the final amino acid sequence. If the change results in a stop codon being prematurely incorporated into the sequence, this is referred to as a  silentnonsensemissensemistranslation mutation.

Genes are not always expressed, as they can be switched off;  growth factorsribosomesoncogenestranscription factors can only bind to DNA to initiate transcription if their binding sites are revealed. Transcription can be inhibited or stimulated by environmental factors such as diet and stress levels, which can affect the levels of mitosis and programmed cell death (  apoptosisnecrosisdestrosisanti-mitosis) occurring.

Genes which determine the body plan of an organism and are expressed during development are called  phagocytichomeoboxstem cellmonogenic genes. They have been discovered in all major animals, plants and fungi, and are highly  differentiatedappreciatedirregularconserved between species.