Epigenetics

Question 1

epigenetics

Answer 1

heritable changes in gene function without changes to base sequence
caused by:
environmental factors can eg smoking + internal signalling
genes do not physically change but the potential for them to be expressed does

Question 2

dna in euk

Answer 2

wrapped around proteins called histones
histones can be chemically modified through addition of acetyl
changed by addition of methyl groups

Question 3

increased acetylation

Answer 3

causes DNA to unwind
acetyl group is added to lysine on histone
replaces a H+ ion on lysine and removes bond between DNA and histone
DNA less tightly wrapped around histone
RNA polymerase + other transcription factors can bind more easily
gene expression is stimulated
switching on

Question 4

decreased acetylation

Answer 4

positive charges increased on histones- acetyl groups removed
attraction to phosphate groups of DNA increased
DNA and histones association stronger, DNA not accessible to transcription factors

Question 5

increased methylation

Answer 5

methyl group added to C on cytosine
suppresses transcription of affected gene
methylated bases attract proteins that bind to DNA and inhibit transcription
prevent the binding of transcriptional factors
switching OFF

Question 6

disease

Answer 6

abnormal methylation of tumour suppressor genes + oncogenes can cause cancer

Question 7

treating disease

Answer 7

epigenetic changes are reversible
drugs can counteract changes that cause diesease
eg drugs that stop DNA methylation (counteract DNA methylation) and allow the gene to be transcribed normally (tumour suppressor genes)
oncogenes- cause cells to divide too quickly
removal of acetyl groups histones attached to oncogenes, DNA wrapped more tightly
stops cancer as faulty cells do not divide