Lecture 2 - RNA and Transcription

Question 1

What was the pulse-chase experiment by Zamecnik and Brenner?

Answer 1

1. Cells exposed to radioactive uracil made RNA with it
2. RNA moved from the nucleus to the cytoplasm proving that it is a messenger
3. mRNA was named

Question 2

What is the central dogma?

Answer 2

The genetic instructions carried by DNA must be transcribed into RNA, which is then translated into a protein

Question 3

Who discovered the enzymes responsible for synthesising RNA and DNA?

Answer 3

Ochoa and Kornberg 1959

Question 4

What is the sugar difference between RNA and DNA?

Answer 4

RNA has a ribose sugar (OH) and DNA as a deoxyribose sugar (H)

Question 5

What is the base difference between RNA and DNA?

Answer 5

RNA has uracil and DNA has thymine

Question 6

Why is RNA more chemically reactive than DNA?

Answer 6

It has 2 x OH groups

Question 7

What are exceptions to RNA‘s usual single stranded structure?

Answer 7

Forming complementary base pairs creating 3D structures, non conventional base pairs (C-U)

Question 8

What does Mesenger RNA do?

Answer 8

Codes for proteins

Question 9

What does ribosomal RNA do?

Answer 9

Forms core ribosomal structure and catalyses protein synthesis

Question 10

What do micro RNAs do?

Answer 10

Regulate gene expression

Question 11

What do transfer RNAs do?

Answer 11

Adapters between mRNA and amino acids during translation

Question 12

What is transcription?

Answer 12

RNA being synthesised for a DNA template by RNA polymerase

Question 13

In eukaryotes which RNA polymerase transcribes mRNA?

Answer 13

RNA polymerase II

Question 14

What is required for transcription?

Answer 14

RNA polymerase enzyme, a DNA double helix and NTP‘s (nucleotides)

Question 15

In what direction is RNA synthesised?

Answer 15

5’ to 3’

Question 16

What bond breaks between RNA and DNA once the RNA is synthesised?

Answer 16

Phosphoanhydride (between the 2 phosphates)

Question 17

Where does the RNA-DNA helix form before its unwound and newly made RNA and double helix DNA reform?

Answer 17

The active site of RNA polymerase

Question 18

Where does transcription occur in a eukaryotic cell?

Answer 18

In the nucleus

Question 19

Where does transcription occur in bacterial cells?

Answer 19

In the cytoplasm near the DNA

Question 20

What occurs to mRNA after translation in only eukaryotic cells?

Answer 20

Pre mRNA is turned into mature RNA in three steps

Question 21

What are the three steps of mRNA processing?

Answer 21

1. 5’ end is capped with an atypical nucleotide
2. 3’ gets a tail of poly-A-nucleotides
3. Introns are removed by the spliceosome which is performed by small nuclear RNA that bind to the proteins forming small nuclear ribonucleoprotein particles.

Question 22

What is alternative splicing?

Answer 22

When more than one protein is expressed from a single gene, such as it being expressed with and without certain introns

Question 23

What occurs to mature RNAs once they’re made?

Answer 23

They are selectively exported from the nucleus with incorrectly synthesised ones being broken down and the nucleotides being reused

Question 24

What determines how much protein is translated in the cell and why?

Answer 24

The stability of RNA that determines how many times the mRNA itself can be translated from