20.4 Epigenetic control of gene expression

Question 1

what is epigenetics

Answer 1

how envrionmental influences (e.g. diet, stress, toxins) can alter the genetic inheritance of an organsims offspring

Question 2

what is the epigenome

Answer 2

the chemical ‘tags’ that cover the DNA and histones

Question 3

what does the epigenome determine

Answer 3

the shape of the DNA histone complex

Question 4

how the epigenome can make genes inactive

Answer 4

DNA and histones in a tightly packed arrangement so they cannot be read
(switched off. known as epigentic silencing)

Question 5

how the epigenome can make genes active

Answer 5

DNA and histones loosely packed (unwrapped) so that DNA is exposed and can be easily transcribed (switched on)

Question 6

difference ebtween DNA code and epigenome

Answer 6

DNA code is fixed

epigenome is flexible

Question 7

how is the epigenome ‘flexible’

Answer 7

chemical tags respond to environmental changes

e.g. diet and stress can ajust the wrapping and unwrapping of the DNA and so which genes swithc on and off

Question 8

why can the epigenome of a cell be described as a cellular memory

Answer 8

it is the accumulation of the signals it has recieved during its life time

Question 9

the environmental signal stimulates…

Answer 9

proteins to carry its message inside the cell into the nucleus where the message passes to a particular protein which can be attached to a specific set of bases on the DNA

Question 10

once protein is attached to specific set of bases on DNA it can have two affects

Answer 10

acetylation of histones -leading to the activation or inhibition of gene
methylation of DNA by attracting enzymes that can add or remove methyl groups