RNA Synthesis

Question 1

What is the definition of intron?

Answer 1

A sequence in the gene DNA that is transcribed as part of the primary RNA transcript
But it’s removed to form the mature mRNA

Question 2

What is the definition of exon?

Answer 2

A sequence in the gene and primary transcript

Retained in the mature mRNA

Question 3

What is the untranslated region?

Answer 3

A sequence in the mature mRNA (the exon sequence)

But this region doesn’t code for amino acids

Question 4

Where do the variety of RNA molecules in eukaryotic cells come from?

Answer 4

They are transcribed from DNA

Question 5

What is the function of snRNA?

Answer 5

Helps align sequences (introns) to be splices out of primary transcripts

Question 6

What is transcription?

Answer 6

Synthesis of an RNA molecule which is complementary to the DNA template strand, but identical to the coding strand

Question 7

What is the function of RNA polymerase?

Answer 7

It uses nucleotide triphosphates (ATP, CTP, GTP, UTP) to synthesise RNA

Question 8

What are the 3 different types of RNA polymerase found in eukaryotes and what are their functions?

Answer 8

RNA polymerase I
-transcribes rRNA genes
RNA polymerase II
-transcribes mmRNA
RNA polymerase III
-transcribes tRNA and other small RNAs

Question 9

How is eukaryotic mRNA modified after transcription?

Answer 9

• it’s capped at 5’ end
• it’s polyadenylated at 3’ end
• splicing- removal of intervening sequences (introns)

Question 10

How is gene expression controlled?

Answer 10

• tissue-specific gene expression
• some genes code for proteins needed for all cells
• some genes are inducible, induced by certain hormones
• some genes are tissue specific, only expressed in certain tissues

Question 11

What are promoters?

Answer 11

• the sequence immediately 5’ to the region being transcribed
• they recruit RNA polymerase to the DNA (RNA polymerase binds to DNA very poorly on its own)
• contain DNA sequences that are very strong binding sites for specificity factors/transcription factors

Question 12

What are transcription factors?

Answer 12

• proteins that bind to specific DNA sequences at promoters
• they control gene expression
• they activate/repress RNA polymerase binding
• they can activate the correct genes as they bind to specific DNA sequences
• only found in promoters of their target genes