Week 1 Lecture 2

Question 1

difference between RNA and DNA

Answer 1

1. DNA- ATCG
   RNA- AUCG
2. DNA- double stranded
   RNA- single stranded
3. DNA- deoxyribose: without oxygen- makes DNA stable
   RNA- ribose: with oxygen- makes RNA unstable

Question 2

structure of RNA

Answer 2

hairpin structure

includes a stem where complimentary base pairing happens but RNA is still single stranded

Question 3

transcription in eukaryotes (4 steps)

Answer 3

1. helicase opens DNA
2. RNA polymerase finds AUG (start codon for methionine)
3. transcription to get pre-mRNA (coding region: gene [coding starts at the promotor])
   *5’ to 3’
4. RNA processing to make mRNA

Question 4

types of RNA

Answer 4

mRNA- encodes amino acids
tRNA- brings amino acids to ribosomes
rRNA- along w ribosomal proteins make up ribosomes
snRNA- makes complexes that are used in RNA processing in eukaryotes

Question 5

coding strand v template strand

Answer 5

coding: identical to mRNA except all Ts are Us

template: used as a template in the synthesis of mRNA

Question 6

mRNA in prokaryotes (5)

Answer 6

1. coding sequence: promotor to terminator
2. transcription takes place
3. 5’ end has a leader sequence
   3’ end has a trailer sequence
4. translation
5. polypeptide

Question 7

mRNA in eukaryotes

Answer 7

1. coding sequence from promotor to terminator along with introns in the middle
2. transcription takes place (pre-mRNA):
   
   • leader and trailer present
   • introns present
     *GTP cap at 5’. poly A tail at 3’.
3. RNA processing: snRNP attaches to intron, loops it out and splices it. only exons left

[*GTP cap used as recognition signal for ribosomes
*poly A tail: 150 or more adenine nucleotides added for stability of mRNA]

Question 8

how does snRNP recognize intron

Answer 8

AG/GT border
CAG/NT border (N=any nucleotide)