1.4 Epigenetic and Mutation

• Genotype


  The genetic code
• Acetylation is where acetyl groups bind to Histone proteins to prevent them from coiling too tightly
• Methylation is where methyl groups are added to the cytosine (C) bases in DNA
• Cell Differentiation


  Cells differentiate (or specialise) into different cell types
• Phenotype


  The observable outcome characteristic that the genotype codes for
• Cell Differentiation is caused by

  Genes being turned on or off in different cells which results in different proteins being made
• Methylation

  Methyl groups block RNA Polymerase= No Transcription= No protein= No Phenotype/Genotype expression
• Certain hormones switch genes on by binding to promoter regions on DNA= Promotes protein synthesis= Gene expression
• Other hormones switch genes off by blocking RNA Polymerase and preventing transcription= No protein= No gene expression
• Non-coding RNA (ncRNA)


  RNA that is transcribed from DNA but not translated into a protein
• Certain environmental epigenetic factors can cause negative effects
• Epigenetics are changes in gene expression that are not due to changes in the DNA sequence (mutations)
• Acetylation


  DNA that is coiled tightly can't be read= Switched off= No protein= No expression
• The Absence of Acetyl groups ‘switches off’ genes
• Environmental factors can impact gene expression
• Without Epigenetics, cells would not differentiate- so epigenetics are good
• Environmental factors

  Affect phenotype expression by impacting the proteins that are made
• All organisms started from a single cell (zygote) which divided to produce multiple cells with the same DNA
• Different proteins are needed for different jobs, e.g., muscle cells don't need the same proteins as eye cells
• Epigenetic factors in parents' cells are passed to offspring through meiosis- genes that are silenced in an egg/sperm cell are also then silenced in the zygote
• Epigenetic factors include Methylation, Acetylation, Non-coding RNA, Hormones, Gene products, and Environmental factors
• Non-coding RNA function by

  Controlling Methylation and Acetylation and other factors controlling gene expression
• The presence of Acetyl groups ‘switches on’ genes
• Methylation can be permanent or temporary
• Gene products


  Sometimes when one gene is expressed, it can affect whether other genes are expressed or not