regulation of transcription and translation

• transcriptional factors:

  transcription of a gene only occurs when a transcriptional factor binds to the base sequence of DNA that came to the cytoplasm to the nucleus

  • creates mRNA which is translated to the cytoplasm to create a protein
• oestrogen

  steroid hormone - lipid soluble - can diffuse through membranes

  • binds to the receptor of transcriptional factor (complementary)
  • changes shape of binding site - 
  • complementary in shape to DNA - activates the transcriptional factors (initiating transcription)
• epigenetics

  heritable change in the gene function without changing the DNA base sequence

  • changes can be caused by environmental changes - inhibits transcription
• environmental changes:

  factors like diet,stress,toxins:

  • adds chemical tags (epigenetics) 

  epigenome (a layer of chemical tags) can impact the shape of the DNA histone complex - whether DNA is tightly coiled or not
• what happens if DNA histone is tightly wrapped

  transcription factors cannot bind - inhibits transcription
• heterochromatin

  DNA is tightly coiled

  transcription is inhibited
• methylation of DNA

  • attaches to cytosine
  • increased methylation - inhibits transcription (prevents transcription factors from binding)
  • attracts proteins and condense DNA-histone complex (tightly coiled together)
• acetylation of DNA

  • decreased acetylation - inhibits transcription
  • histones become more positive and attach to phosphate group - DNA
  • harder for transcription factors to bind
• RNA interference (RNAi)

  translation can be inhibited by RNAi (eukaryotic)

  mRNA is destroyed before it can be used to create polypeptide chain
• process of RNAi

  siRNA combine with another enzyme - siRNA-enzyme complex

  can bind to complementary base sequences of mRNA

  enzymes will cut the mRNA - can not be translated