16. HISTONES Flashcards
1
Q
- What can Histones undergo?
A
- they can undergo Chemical Modifications
(methylation, acetylation) - these result in changes in the chromatin organisation
- this results in changes in the gene expression
2
Q
- What kind of gene expression changes can be caused by Histone chemical modifications?
A
- gene silencing
(the inhibition of a gene) - this is often involved in many diseases
(cancer)
3
Q
- What are Epigenetics?
A
- this is the study of cellular and physiological traits
- these traits are not caused by changes in the DNA
sequence - these are caused by changes in the gene expression
4
Q
- What 2 modifications can cause an Epigenetic change in cellular or physiological traits?
A
- DNA Methylation
- Histone Modification
5
Q
- What are 2 types of Histone modifications?
A
- Histone Acetylation
- Histone Deacetylation
6
Q
- What is Histone Acetylation?
A
- this is the conversion of Heterochromatin into
Euchromatin
7
Q
- What happens during Histone Acetylation?
A
- there is the loss of the histone’s positive charge
- this is due to the acetylation
- as it weakens the interaction of histones with DNA
- this loosens the chromatin
NB:
- the DNA is negatively charged due to its phosphate
group
8
Q
- What is the result of Histone Acetylation?
A
- the chromatin is converted into its loose active form
(Euchromatin) - this enables gene expression
9
Q
- Can you remember 3 Amino Acids that are positively charged?
A
- Lysine
- Arginine
- Histidine
10
Q
- What is Histone Deacetylation?
A
- this is a process that inactivates the chromatin
- it converts it into heterochromatin
- it restores the positive charge of the histone
- this then strengthens the interaction between the
histone and DNA
11
Q
- Which Enzyme is present during Histone Acetylation?
A
- HAT
- Histone Acetyl-Transferases
12
Q
- Which Enzyme is present during Histone Deacetylation?
A
- HDAC
- Histone Deacetylases
- an over-expression of this enzyme can cause cancer
13
Q
- Does this diagram make sense?
A
- yes
