epigenetics Flashcards
State what is meant by epigenetics
Heritable changes in gene function due to environmental factors that do not change the base sequence of DNA
Describe the nature of the epigenome
The epigenome is a series of chemical tags attached to DNA and histones that affects the transcription of DNA
all the chemical tags on DNA and histones of an organism
define genome
the entire set of genetic material a cell/organism posseses
Explain the effect of epigenetic factors on DNA and histones
The epigenome determines the shape of the DNA-histone complex by changing how tightly wrapped the DNA is. When tightly wrapped the DNA cannot be transcribed, when loosely coiled DNA can be transcribed
explain what happens when an environmental factor binds to a receptor
environmental factor binds to a receptor on cell surface membrane causes a 2nd messenger system causing an enzyme to be activated which adds or removes methyl or acetyl groups
Explain the effects of decreased acetylation of histones
- acetyl groups are being removed ( decreased acetylation)
- causing histones to have a positive charge which are attracted to the negative charge of phosphates causing DNA to coil and condense
- no binding of transcription factors
- preventing RNA polymerase from binding
- no transcription
- no gene expression
define acetylation of histones
acetyl groups bind to histone proteins
define methylation of DNA
addition of methyl groups (- CH3) to cytosine bases on DNA
Explain the effects of increased methylation of DNA
Gene switched off (inactive):
Increased methylation of DNA
Prevent binding of transcriptional factors to DNA
Attract proteins that condense DNA/histone complex by inducing deacetylation
Genes tightly packed (condensed)
Transcriptional factors cannot bind
Transcription cannot occur so mRNA is not made
Protein is not produced
