20.4 epigenetic control of gene expression Flashcards Preview

bio: section 8 > 20.4 epigenetic control of gene expression > Flashcards

Flashcards in 20.4 epigenetic control of gene expression Deck (16):
1

define epigenetics

process by which environmental factors can cause heritable changes in gene function without changing the base sequence of DNA

2

define epigenome

chemical tags that determine the shape of the chromatin

3

which bit of the contents of the nucleolus is fixed?

DNA

4

which bit of the contents of the nucleolus is flexible

epigenome

5

what do the epigenetic tags respond to?

signals in the environment e.g. diet, stress and toxins

6

how does the epigenome adjust the chromatin?

- makes some chromatin tightly wrapped so are inaccessible to transcriptional factors
- makes some chromatin loosely packed so are easily accessible to transcriptional factors

7

what are the 2 ways in which signals from the environment can caused condensation of the chromatin?

- decreased acetylation of histones
- increased methylation of DNA

8

how does decreased acetylation of histones cause the gene to become inaccessible?

- increases the positive charges on the histones
- increases the attraction to the phosphate group on the DNA
- gene switched off

9

what are the 2 ways in which increased methylation inhibits transcription of genes?

- preventing the binding of transcriptional factors to the DNA
- induced deacetylation, making the DNA inaccessible to transcriptional factors

10

acetylation definition

process where an acetyl group is transferred to a molecule

11

deacetylation definition

process where an acetyl group is transferred from a molecule

12

methylation definition

process where a methyl group is transferred to a molecule

13

demethylation definition

process where a methyl group is transferred from a molecule

14

what is the increased methylation of DNA?

methyl group is added to the cytosine bases of DNA

15

what are 2 ways in which cancer can be caused?

- activation of a normally inactive gene
- inactivation of a normally active gene

16

describe the process in which RNA interference effects gene expression

1. double stranded RNA is broken up by an enzyme into siRNA
2. 1 of the 2 strands of siRNA combines with an enzyme
3. siRNA pairs with complementary bases on mRNA strand
4. enzyme cuts the mRNA into smaller sections