Gene Expression

Transcription factor

Protein or molecule that moves from the cytoplasm to the DNA and binds to a specific base sequence of the DNA molecule

Promotor

DNA sequence before gene allowing RNA polymerase to bind to initiate transcription

How do hormones/oestrogen effect transcription

• Oestrogen binds to the receptor as complementary in shape

• Shape of DNA binding site changes

• Easier for RNA polymerase to bind to promotor

• Binds to the promoter on the DNA

• transcription occurs

Epigenetics

Environmental factors can cause heritable changes in gene function without changing the base sequence of DNA

Adding methyl groups to DNA

• DNA more tightly packed

• harder for genes to be transcribed

• TF cannot bind

• genes not expressed

Adding acetyl groups to histones

• DNA more loosely packed

• genes can be transcribed more easily

• TF can bind

• genes expressed

Why is the epigenome flexible

Chemical tags can be removed/added in response to environmental changes which will change the DNA-histone complex structure and cause to be switched on/off

Environmental factors

• diet

• stress

• toxins

• age

RNAi

1= Large double stranded RNA molecules are cut into smaller sections called small interfering RNA by an enzyme

1= Lots of siRNA produced around 21 nucleotides long

2= One of the 2 siRNA strands (guide strand) combines with an enzyme

3= The siRNA guide strand guides the enzyme to the mRNA and the siRNA guide strand pairs with complementary bases on a mRNA strand

4= The enzyme cuts the mRNA into smaller sections so it can no longer be translated