6.1.5 Gene Control: Post-Transcriptional Modification

Question 1

What are exons

Answer 1

Coding sequences eventually translated into amino acid forming final polypeptide

Question 2

What are introns

Answer 2

Non-coding sequences that are not translated

Question 3

What happens to introns and exons during transcription?

Answer 3

• They are both transcribed
• mRNA contains introns and exons
• Known as primary mRNA or pre mRNA

Question 4

What happens to primary mRNA before translation?

Answer 4

• Post transcriptional modification
• Splicing
• Removal of introns
• So only coding sections of mRNA (exons) present
• Exons fuse together forming mature mRNA
• Ready for translation

Question 5

What happens after translation?

Answer 5

• Golgi apparatus modifies polypeptides
• Some polypeptides may require activation by cAMP (derived from ATP)

Question 6

What does cAMP do (in this context)?

Answer 6

• Activates polypeptides
  Eg. Can activate glycogen phosphorylase
• When muscle cells require energy, this polypeptide enzyme is activated by cAMP, changing the shape of the enzyme exposing its active site ready to convert glycogen to glucose