3.8.2 Gene Expression Flashcards
What is epigenetic imprinting?
Environmental factor
Without change in gene
Give the meaning of the term epigenetic control
Change in gene expression without changing the base sequence of DNA
Heritable
Describe how the production of siRNA reduces the expression of a particular gene
siRNA binds to a protein complex
ATP used to separate double stranded RNA into single strands
Single strands bind to mRNA by complementary base pairing
mRNA cut into fragments
mRNA can no longer be translated
More mRNA in a cell = more siRNA produced
Totipotent cells translate
Only part of the DNA
Causes cell specialisation
How are induced pluripotent stem cells made + why
Genes switched off that make cell specialised
Using transcription factors
Overcomes ethical issues of using embryonic stem cells
What do transcription factors do
Turn on or off genes so only certain proteins are produced
Causes cell specialisation
Affect of decreased acetylation
Inhibits transcription
Acetyl groups negatively charged
Histones positive
When removed from DNA, Histones become more positive
More attracted to phosphate group on DNA
DNA + Histones more strongly associated
Hard for transcription factors to bind
Benign tumour properties
Produce adhesive molecules that stick them together and to a particular tissue
Surrounded by capsule so they remain compact
Cells retain function and normal shape
Slow growth
Can be removed by surgery
Rarely return
Malignant tumour properties
Large cell nucleus
Cell can become unspecialised again
Don’t produce adhesive
Metastasise - tumour breaks off + spreads to other parts of the body
Cells don’t retain function + often die
Not encapsulated - grows projections + develop own blood supply
Chemotherapy and radiotherapy often required
Recurrently more likely
What do proto-oncogenes do
Code for proteins involved in initiating DNA in cell cycle
What do oncogenes do
Result in process making proteins activated at all times
Cells divide continually even when not required
Affects of Hyper methylation + Hypo methylation
Hyper- increased number methyl groups attached - gene turned off
Hypo- reduced number methyl groups- gene permanently turned on
Knock on affect of tumour in breast tissue
As tumour grows, more breast tissue cells are present
More oestrogen produced
More proto-oncogenes switched on
More cell division
What happens to Totipotent cells during embryonic development
Certain parts of the DNA are selectively translated so that only some genes are ‘switched on’ in order to differentiate the cell into a specific type and form the tissues that make up the foetus
Unique feature of pluripotent cells + the use
Divide in unlimited numbers
Can be used to repair or replace damaged tissue
