37. CO-EXPRESSION OF GENES

Question 1

1. What can be said about functionally related genes of a Prokaryote Operon?

Answer 1

• they are regulated by the same promoter
• they produce a Polycistronic mRNA molecule

Question 2

2. What does the polycistronic mRNA molecule do?

Answer 2

• it encodes for more than one polypeptide
• this gene can be co-expressed

Question 3

3. What can be said about Eukaryotic genes?

Answer 3

• each Eukaryotic gene has its own promoter
• it also has its own control elements

THESE GENES PRODUCE:
- a Monocistronic mRNA

Question 4

4. What does the Monocistronic mRNA code for?

Answer 4

• it encodes for only 1 polypeptide

Question 5

5. What can be said about functionally related genes?

Answer 5

• they have the same control elements
• they have the same activators
• even if they are found on different chromosomes

Question 6

6. What do Activators do for Eukaryotic cells?

Answer 6

• they recognise the specific control elements
• they promote the transcription of genes
• these genes are co-expressed

Question 7

7. What is the Combinational Control of Gene Activation?

Answer 7

• this is a combination of control elements
• it allows the activation of transcription
• only when the appropriate activator proteins are
  present

Question 8

8. What is an example of Combinational Control of Gene activation?

Answer 8

• liver cells and lens cells
• they both have genes for making albumin and
  crystalline proteins
• only liver cells make albumin
• only lens cells make crystalline

Question 9

9. What is Post-Transcriptional Regulation?

Answer 9

• these are regulatory mechanisms
• they operate at various stages after transcription

Question 10

10. What does Post-Transcriptional Regulation provide?

Answer 10

• it provides rapid regulation of the gene expression
• this is done in response to environmental changes

Question 11

11. What are the 4 steps of Post-Transcriptional Regulation?

Answer 11

1. RNA Processing
2. mRNA Degradation
3. Initiation of Translation
4. Protein Processing and Degradation

Question 12

12. What method is used for RNA Processing?

Answer 12

• Alternative Splicing

Question 13

13. What does Alternative Splicing produce?

Answer 13

• it produces many different mRNA molecules
  from the same primary RNA transcript

Question 14

14. What does Alternative Splicing depend on?

Answer 14

• it depends on what segments of the primary RNA
  transcript are considered to be introns and exons

Question 15

15. What results in some types of Beta Thalassaemia?

Answer 15

• the abnormal alternative splicing of the Beta Globin
  gene

Question 16

16. What is the key to determining Protein Synthesis?

Answer 16

• the life span of the mRNA molecules

Question 17

17. Which lives longer: eukaryotic or prokaryotic mRNA?

Answer 17

• Eukaryotic

Question 18

18. What partially determines the mRNA molecule life span?

Answer 18

• the sequences found in the 3’ UTR
• this is the untranslated region

Question 19

19. What induces mRNA degradation?

Answer 19

1. Nucleases
2. Non-coding RNAs

• they inhibit gene expression