Histone modification

Question 1

Why does DNA coil around histones?

Answer 1

• histones are positively chargged
• DNA is negatively charged

Question 2

How can histones be modified?

Answer 2

to increase or decrease the degree of condesation (or packing) or increase the tightness of DNA

Question 3

How is the charge of histones reduced?

Answer 3

• addition of:
  
  • acetyl groups (acetylation)
  • or phosphate groups (phosphorylation)
• makes them more negative - decreases the positive charge

Question 4

How is the charge of histones increased?

Answer 4

• addition of metyl groups (methylation)
• makes the histones more hydrophobic
• as a result they bind more tightly to each other causing DNA to coil more tightly

Question 5

What is the effect of histones modification?

Answer 5

• decrease charge of histones
  
  • coil less tightly
  • allo0wing certain genes to be transcribed
• increase the charge
  
  • DNA coil more tightly
  • prevents transcription of genes

Question 6

WHat is epigenetics?

Answer 6

• term used to describe this control of gene expression by the modification of DNA
• sometimes used to include all of the different ways in which gene expression is regulated