Transcription/Translation

Question 1

How many chromosomes do prokaryotes have?

Answer 1

1 pair

Question 2

Transcriptional differences

Answer 2

prokaryotes have operons, polycistronic mRNA, no hnRNA (introns), no histones, circular DNA

• and translation and transcription happen at the same time in the cytosol
• NO mRNA processing

Question 3

How is Eukaryotic DNA packed

Answer 3

alpha helix - histones - nucleosomes - chromosomes

less than 2% of the DNA in the chromosome is actually coding DNA, extrons

Question 4

tRNA role

Answer 4

brings the AAs to ribosome for protein synthesis

Question 5

name for the strand of DNA that gets transcribed

Answer 5

template strand

Question 6

name for the strand of DNA that is identical to the mRNA synthesized, except with T replaced by U

Answer 6

coding strand

Question 7

Are promoters found in Prokaryotic or Eukaryotic DNA?

Answer 7

both! you mother fucker

-TATA box is an essential component of the promoter region. It helps the transcription machinery find the right start site

Question 8

RNA polymerases

Answer 8

–Don’t need a primer

-have no 3’ to 5’ exonuclease capability (higher error rate than DNA)

Question 9

Name the RNA polymerases in Eukaryotes and their function.

Answer 9

RNA pol I - synthesizes the most RNA - rRNA
RNA pol II - makes the second most amount - mRNA
RNA pol III - makes the least amount of RNA - tRNA

Question 10

What happens when RNA pol I, II, or III is not working

Answer 10

I - less protein synthesized (no fucking ribosomes)
II- less protein synthesized (no fucking directions)
III - no protein synthesized (no AA are retrieved for syn)

Question 11

Prokaryotic RNA pol

Answer 11

only one, that makes all 3 types of RNA

requires a sigma factor

Question 12

What the hell is alpha amanitin?

Answer 12

its a toxin from mushrooms that blocks RNA pol II
decreasing mRNA in cell (especially GI cells, because new ones cant make mRNA without RNA pol II)
no cure so you could die in a few days if you get a big dose

Question 13

Prokaryotic transcription

Answer 13

RNA polymerase, template DNA, sigma factor, Rho factor, nucleotides (A, U, C, G)

Question 14

sigma factor

Answer 14

helps get RNA pol to the start site

Question 15

Rho factor

Answer 15

required for termination

Question 16

Don’t forget about differential splicing, euk or prok?

Answer 16

Allows *Eukaryotes to form many different gene products

Question 17

What is mature mRNA

Answer 17

spliced + cap and tail

-occurs in nucleus before leaving for cytosol

Question 18

purpose of 5’ cap and polyA tail

Answer 18

• protects 5’ end and allows for ribosome binding

- prevents degradation

Question 19

Key differences in Eukaryotic transcription (that you dont already know)

Answer 19

no sigma factor, instead requires multiple general transcription factors
Its moncistronic: 1 mRNA = 1 protein
requires this polyadenylation signal (AAUAAA)
*and of course stuff to cut DNA for splicing (endonuclease) - prokaryotic DNA is not spliced

Question 20

Beta-thalassemia

Answer 20

decreased number of Hb molecules due to a mutation causing decreased transcription of the gene

Question 21

miRNA?

Answer 21

miRNA regulate mRNA transcript stability.

Question 22

A patient is found to have deficiency in a chloride channel, CFTR, that is traced to a mutation in the 3′ end of the gene, where the sequence AATAAA is found mutated to AAGAAA. What effect will this have?

Answer 22

The mRNA will not be able to leave the nucleus (needs cap/poly A tail/needs splices – if its mutated wont get a poly A tail) – mutation is affecting the transcript (if you cant get transcript into cytoplasm wont make the protein)

Question 23

Many antibiotics work by inhibiting bacterial mRNA synthesis. Rifamycin, for example, blocks transcription in E. coli. How is it possible that this drug is such a potent antibiotic to E. coli, yet does not cause harm to the person taking it?

Answer 23

• Could be due to difference in RNA polymerase
• Or Ribosome has different subunits in prok and eukary
• Could block the sigma factor
• **Sigma factor, polymerases are different, and ribosomes are different (anything that targets the difference in bacteria and us)

Question 24

What would prevent the production of a normal transcript in bacteria?

Answer 24

Bacteria: Lack of sigma factor, lack of Rho factor, problem with RNA polymerase,

Both: (TATA box or promoter, lack of nuceotides, lack of ATP

Question 25

What would prevent the production of a normal transcript in humans (eukaryotes)?

Answer 25

Euk: failure to splice, poly A tail or cap failure, problem unwinding DNA (issue with histones), lack of specific transcription factors (ones that enhance transcription)

Question 26

4 letter alphabet
3 letter code
how many possible combinations/codons?

Answer 26

4x4x4 = 64 (we dont have this many - its redundant, BUT not ambiguous)

Question 27

Name the start codon and stop codons

Answer 27

start codon = AUG (ATG if asked for coding DNA sequence)

Stop: UAA, UAG, UGA

Question 28

Types of mutations?

Answer 28

point mutation - single base change
silent mutation - change results in same AA
missense mutation - specifies a different amino acid
non-sense mutation - produces a stop codon
insertion/deletion - results in frameshift mutation unless an entire codon is inserted or deleted