regulation of transcription and translation Flashcards
regulation of transcription
in eukaryotes, transcription is stimulated/inhibited by transcription factors
these are proteins which move from the nuclues to the cytoplasm and bind to DNA to intiate transcription.
if the genes are not activated, transcription doesn’t occur and the protein is not produced
switching on/off genes is what makes a cell specialised
oestrogen as a transcription factor
oestrogen is a steroid hormone
lipid soluble so can diffuse across the phospholipid bilayer
binds to receptor on DNA and changes shape of transcription factor
transcription factor becomes complimentary so can bind to DNA and initiate transcription.
regulation of translation
in eukaryotes and some prokaryotes, the translation of mRNA transcribed from a target gene is inhibited by RNA interference
carried out by small interfering RNA/siRNA
1) enzyme cuts RNA into siRNA
2) one strand of the siRNA binds to an enzyme
3) siRNA enzyme complex binds to mRNA by complimentary base pairing
4) once bopundd
methylation of DNA
as methylation of DNA increases, it inhibits transcription
the methyl groups added to the DNA attach to the cytosine base
so this prevents transcription factors from binding and attracts a protein which condenses the DNA histone complex
so some sections of DNA are not transcribed
epigenetics
gene expression/protein synthesis is controlled by epigenetics
epigenetics is the heritable change in gene function without changing DNA base sequence
changes are caused by changes in the environment and can inhibit transcription
acetylation of histone proteins
as acetylation of histone proteins decreases, transcription decreases
if acetyl groups are removed from histone proteins of DNA
histone proteins become more positive
more strongly attracted to phosphate of DNA
DNA and histone proteins associate more strongly so hard for transcription factor to bind
