2. Regulation of gene expression

Question 1

what is an exon?

Answer 1

the coding, or expressed, region of DNA

Question 2

what is an intron?

Answer 2

the non-coding region of the DNA

Question 3

what is an operon?

Answer 3

a group of genes that function together and code for enzymes that control a particular metabolic pathway

Question 4

what is the lac operon?

Answer 4

a section of DNA within a bacterium that codes for the enzymes that metabolise lactose

Question 5

what makes up the lac operon?

Answer 5

lacZ which codes for B- galactose and lacY which codes fir lactose permase

Question 6

what is a regulatory gene?

Answer 6

the regulatory gene codes for a repressor protein which binds to the operator and prevents the transcription of lacZ and lacY so enzyme for lactose metabolism are not made

Question 7

what are transcription factors?

Answer 7

proteins, short non-coding pieces of RNA that act within the cell’s nucleus to control which genes in a cell are turned on and off. they may aid or inhibit the attachment of RNA polymerase to the DNA
essential to ensuring the genes in a cell are either activated or suppressed
some transcription factors can regulate the cell cycle

Question 8

what happens at post transcriptional level?

Answer 8

• when transcription of a gene occurs, both the exons and introns are transcribed
• which results in primary mRNA
• introns do not need to be translated so must be removed
• introns are removed and the exons are joined together
• this process is called ‘splicing’ and is catalysed by endonuclease enzyme
• if introns are in the final mRNA the resulting protein may not be able to carry out its function

Question 9

what happens at post-translational gene expression? (simple)

Answer 9

activation of proteins by cyclic AMP

Question 10

what is cAMP?

Answer 10

cyclic adenine mono phosphate which is synthesised from ATP using adenylate cyclase enzyme inside the plasma membrane
cAMP targets a group of proteins called kinases

Question 11

what is the process of post- translational level?

Answer 11

• cAMP activates protein kinase A
• activated protein kinase A catalyses the phosphorylation of various proteins, hydrolysing ATP in the process
• this activates many enzymes in the cytoplasm
• cAMP activates proteins and causes conformational change in the shape, which allows molecules to bind to active site better
• this then enters the nucleus and acts as a transcription factor, to regulate transcription