9. epigenetics

• DNA methylation?

  • methyl groups attach to DNA bases and stop RNA polymerase from binding to DNA
  • gene off, transcription cannot occur so no mRNA/protein made and no gene expressed
• histone modification?

  • methyl/acetyl groups attach to histone tail and affect how tightly DNA winds around histone
  • tight: gene isn't accessible, switched off and cannot be transcribed to form mRNA. no protein= no gene expressed
  • loose: gene is accessible, can be transcribed and expressed
• agouti gene- behaviour?

  bad mother looking after offspring of good mother:

  • GR gene methylated and not expressed. GR receptor protein isn't produced. when exposed to stress, glucocorticoid levels are high and offspring shows high anxiety and low licking
• DNA?

  • triplet code, 3 bases
  • degenerate, more than one codon
  • universal, same code in all org
  • non-overlapping, discrete reading frames