Transcription Of Genes

Question 1

Central dogma

Answer 1

Transcription is the first step of converting information encoded in the DNA into proxim or other functional units in the cell.

Question 2

The interaction of transcription and translation in prokaryotes and eukaryotes

Answer 2

• all in a single compartment in prokaryotes
• different spatial location in eukaryotes - mean a temporal separation too

Question 3

Starting with prokaryotes

Answer 3

• enzyme involved is called RNA polymerase - only one RNA poly in prokaryotes.
• RNA polymerase binds to the promoter region with the aid of a sigma factor - helps RNA poly to recognise the promoter sequence.
• RNA polymerase unwinds small aregion DNA at the promoter
• single stranded DNA acts as template for the RNA synthesis
• RNA polymerase tracks along DNA, reading the bases and making RNA bases on the DNA sequence. Synthesis is in the 5’ to 3’direction
• The DNA is unwound and rewound in the process

Question 4

Eukaryotic transcription

Answer 4

• Same basic 3 steps
  Initiation, more complex
  Elongation
  Termination

Question 5

Initiation

Answer 5

1)A eukaryotic promoter includes a TATA box
2)Several transcription factors must
bind to the DNA before RNA
polymerase II can do so
3)Additional transcription factors
bind to the DNA along with RNA
polymerase II, forming the
transcription initiation complex.

More factors involved in starting up eukaryotic transcription
More that one kind of RNA polymerase, however most genes encoding proteins use RNA polymerase II for transcription

Question 6

Eukaryotic control

Answer 6

• Many different kinds of proteins involved
– Activator proteins which bind to DNA
– Mediator proteins
– General transcription factors
– DNA-bending protein
• The mediator proteins interact with the activator proteins bound to the enhancer region
• Help RNA poly II to bind to the promoter

Question 7

Differential control

Answer 7

• Different cells express different panels of genes
• Many of the control factors are common
• Specific activators in different tissues

Question 8

Eukaryotic RNA is processed

Answer 8

• The machinery in the eukaryotNic cell to cut out introns is composed of both protein and RNA
• Work together to achieve result
• They bind to pre-RNA recognising sequences in the intron
• Together they form the spliceosome
• Join the ends of the exons togethe