Transcription

Question 1

What is RNA?

Answer 1

•	RNA (ribonucleic Acid):
o	4 bases: Adenine, Guanine, cytosine & Uracil.
o	Uracil = pyrimidine
o	Ribose (5C) + phosphate
o	Single stranded.

Question 2

What are the Differences:DNA vs RNA?

Answer 2

o	Ribose not deoxyribose
o	Uracil not thymine
o	RNA is easily altered
o	RNA is single stranded
o	RNA is shorter
o	RNA doesn’t usually form a stable secondary structure.

Question 3

What are the types of RNA?

Answer 3

• m/t/r.

Question 4

Describe Messenger RNA (mRNA).

Answer 4

o Variable sizes
o Observed synthesis of certain enzymes is rapidly turned on and off = mRNA must be rapidly made and short lived.
o RNA is complementary to its DNA template.

Question 5

What is a gene?

Answer 5

• Genes are small sections of the DNA genome which can code for a particular protein/RNA.

Question 6

Describe Transcription: describe the steps and regions of DNA/ proteins involved at each step .

Answer 6

LONG.

Question 7

What parts of DNA are transcribed?

Answer 7

o Not all DNA is transcribed into RNA but transcribed in small units containing 1+ genes.

Question 8

What is an area of DNA called if it transcripts one gene? Multiple?

Answer 8

o Monocistronic transcripts just 1 gene – polycistronic transcripts for 1+ genes.

Question 9

Describe initiation.

Answer 9

1 .Initiation:
• Promoter regions (start signal) - recognised by RNA polymerase shows where to initiate transcription upstream from start codon.
• Promoter may also bind with other proteins (transcription factors) – control levels of gene transcription.
• Once RNA polymerase binds to promoter transcription initiates.
• NO PRIMER REQUIRED.

Question 10

Describe elongation.

Answer 10

• The carrying on of RNA polymerase reading the DNA template to produce more of the RNA strand.

Question 11

Describe termination.

Answer 11

• At transcriptional terminator (stop signal) ne RNA is released.
• RNA polymerase dissociates from the DNA.

Question 12

Describe RNA Polymerase. What does it need? What can it do?

Answer 12

o RNA produced from DNA dependant RNA polymerase.
o RNAP relies of DNA template & nucleoside triphosphate precursors (no primer needed).
o Can bind and unwind DNA.
o Ability to know where to stop and start transcription.

Question 13

Describe RNA processing and Exons & Introns. What is added to each end? What removes non-coding sections?

Answer 13

o Exons are the coding sequences and are split by introns- non-coding sequences. Introns=n Exons=n+1
o RNAP transcribes both exons and introns (cannot tell the difference).
o A modified G-CAP is added to the 5’ end.
o Introns are then spliced out by a spliceosome.
o A polyA tail is then added to the 3’ end.
o The mature RNA is the transported to the cytoplasm for translation.

Question 14

What are prok/euk difference?

Answer 14

o Prokaryotes can have polycistronic mRNA = codes for 2+ proteins.
o Eukaryotes only have monocistronic mRNA = codes for 1 protein.

Question 15

What is the role of Transcription in disease:.

Answer 15

o Transcription factors and promotors play a major part in health and disease.

Question 16

What is a tumour suppressor?

Answer 16

o P53= tumour suppressor (guards cancer)- mutation in this gene reason for 50% of cancers. Majority of other 50% from mutations affecting p53 function.

Question 17

What treats breast cancer?

Answer 17

• Tamoxifen – inhibits oestrogen by binging to its receptor- therefore turns off production of oestrogen.

Question 18

What disease is due to mutations in a transcription factor that leads to inappropriate transcription of several genes?

Answer 18

• Rett syndrome: neurodevelopmental disorder affecting 1/15000 female births- detected after 1st birthday – loss of speech and motor skills.
  o Due to mutations in transcription factor that would normally reduce transcription leads to inappropriate transcription of several genes- caused by mutation in male spermatogenesis.

Question 19

What is the difference between humans and other mammals in Transcription and evolution:.

Answer 19

o Differences between humans and other mammals, is due to the same set of genes being regulated. o Most differences are due to changes in promoter sequences.

Question 20

What gene is involved in learning, memory &experience of pain & social bonding? What animal is it higher in?

Answer 20

• Dynorphin

o Dynorphin is higher in humans due to differences in the promoter region.

Question 21

What makes Bat forelimbs are longer?

Answer 21

• partly due to increased expression of transcription factor Prx1. (can be inserted into mouse).