34. EUKARYOTIC GENE EXPRESSION

Question 1

1. What does Gene Expression do in Eukaryotes?

Answer 1

• gene expression is responsible for development
• it is responsible for cell specialisation
• this is known as Differentiation

Question 2

2. What is Differential Gene Expression?

Answer 2

• the expression of different genes
• these genes are expressed by cells with the same
  genome
• this produces different types of cells

Question 3

3. What can be said about almost all the cells in an organism?

Answer 3

• almost all the cells are identical
• a typical human cell only expresses 20% of its genes at
  any given time

Question 4

4. What causes the differences in cell types?

Answer 4

• the different gene expressions

Question 5

5. What percentage of DNA codes for proteins?

Answer 5

• only 1.5% of DNA
• the rest of the DNA codes for the RNA products
• some DNA is not transcribed at all

Question 6

6. What do abnormalities in gene expression lead to?

Answer 6

• different kinds of diseases
• such as cancer

Question 7

7. What can be said about the regulation of genes?

Answer 7

• they are regulated at many stages

Question 8

8. In which 3 cases can eukaryotic gene expressions be regulated?

Answer 8

1. REGULATION
   - of the chromatin structure
   - this consists of Histone Acetylation
   - this consists of DNA Methylation
2. REGULATION
   
   • of transcription initiation
3. POST-TRANSLATION REGULATION
   
   • RNA processing
   • mRNA degradation
   • initiation of translation
   • protein processing
   • protein degradation

Question 9

9. List 3 characteristics of Human DNA.

Answer 9

1. It is 6.3 Gigabase pairs long
2. It is 205 cm long
3. It weights 6.4 picograms per cells

Question 10

10. What is the DNA of eukaryotic cells packaged with?

Answer 10

• proteins
• these are known as histones
• this is packed into Chromatin

Question 11

11. What are the two types of chromatin?

Answer 11

1. Euchromatin
2. Heterochromatin

Question 12

12. What is Euchromatin?

Answer 12

• this is the active form of chromatin
• it is loosely packaged
• it activated Gene expression

Question 13

13. What is Heterochromatin?

Answer 13

• this is the inactive form of chromatin
• it is highly packaged
• it inactivates gene expression

Question 14

14. What are the 3 aspects of the Regulation of the Chromatin Structure?

Answer 14

1. Chromatin Modifications
2. Epigenetic Inheritance
3. Chromatin Modifying Enzymes

Question 15

15. What is Chromatin Modification?

Answer 15

• these are the chemical modifications to histones
• it is chemical modifications to DNA
• this DNA influences the chromatin structure
• this influences the gene expression

Question 16

16. What is Epigenetic Inheritance?

Answer 16

• this is the inheritance of traits
• these traits are transmitted by mechanisms
• these traits are independent of the changes in the
  nucleotide sequence
• they are independent of any chromosome
  modifications

Question 17

17. What are Chromatin Modifying enzymes?

Answer 17

• they are enzymes
• they control gene expression
• they do this by increasing or decreasing the ability of
  the transcription machinery to bind to the DNA

Question 18

18. List 2 examples of chromatin Modifying Enzymes.

Answer 18

1. Histone Acetyl-Transferase
2. Histone Deacetylases

Question 19

19. Which 2 mechanisms does Chromatin Modification make use of?

Answer 19

1. Histone Modifications
2. DNA Methylation

Question 20

20. What is a Nucleosome?

Answer 20

• this is the basic structural unit of DNA packaging
• in eukaryotes

Question 21

21. What does a Nucleosome consist of?

Answer 21

• a segment of DNA
  (less than 2 turns of DNA)
• these are wrapped around a set of eight histone
  proteins
• this is known as a Histone Octamer

Question 22

22. What does a Histone Octamer consist of?

Answer 22

2 COPIES OF EACH OF THE HISTONE PROTEINS:
- H2A
- H2B
- H3
- H4