FoM:L2 - RNA and Genes

Question 1

What is RNA?

Answer 1

• linear polymer
• single stranded
• contains ribose
• A, C, G and U

Question 2

What are the different types of RNA?

Answer 2

• mRNA - codes for proteins
• rRNA - forms basic structure of ribosome
• tRNA - protein synthesis as adaptors between mRNA and AAs
• snRNA (small nuclear) - nuclear processes eg splicing
• snoRNA (small nucleolar) - process and modify rRNAs

Question 3

How is RNA produced?

Answer 3

• transcription
• RNA polymerase (5’ - 3’)
• DNA template produces complementary RNA

Question 4

What are the 3 steps in RNA synthesis?

Answer 4

• initiation: at promoter, RNA pol. binds
• elongation: RNA pol. makes RNA copy complementary to template
• termination: stops

Question 5

What is RNA polymerase holoenzyme?

Answer 5

• bacterial RNA polymerase
• 4 types of subunit
• sigma unit destabilises RNA polymerase so it only binds to promoter sequences

Question 6

What are promoters?

Answer 6

• sites of transcription initiation
• recognised by a consensus DNA sequence
• asymmetric so RNA polymerase knows which way to go

Question 7

What are eukaryotic promoters?

Answer 7

• general transcription factors: help RNA pol. II to bind
• transcriptional activators : attract RNA pol. II, regulate rate and specificity

Question 8

What tells RNA polymerase to stop?

Answer 8

prokaryotes: termination sequences
eukaryotes: polyadenylation signal

Question 9

Outline the genome of a retrovirus

Answer 9

• single stranded RNA
• copied into DNA of host cells
• reverse transcriptase

Question 10

Outline the life cycle of a retrovirus

Answer 10

• enters cell
• reverse transcriptase converts viral RNA to DNA
• viral DNA integrated into host cell’s DNA
• transcription and translation to form viral proteins

Question 11

What are nucleoside analogues?

Answer 11

compete with normal bases and terminate DNA chain elongation

Question 12

What is a gene?

Answer 12

• a DNA sequence that encodes for an RNA product
• open reading frame

Question 13

What is heterochromatin?

Answer 13

• condensed inactive and repetitive DNA
• in centromeres

Question 14

What are transposons?

Answer 14

• copies of short DNA sequences
• self-replicating stretches that insert themselves in other DNA
• some use RNA intermediate
• can cause disease if inserted in/near a gene