Lecture 2

Question 1

RNA vs. DNA

Answer 1

1) single stranded vs. double stranded
2) uracil vs. thymine
3) ribose (OH) vs. deoxyribose (H) on 2’ carbon

Question 2

Define mRNA

Answer 2

messenger RNA
-transcripted from template DNA
-translates/codes for proteins

Question 3

Define tRNA.

Answer 3

-transfer RNA
-pairs codons (mRNA–> anticodon (complimentary) with amino acids (CCA terminus)

Question 4

Define rRNA

Answer 4

-ribosomal RNA
-combines with proteins to form ribosome for translation

Question 5

IN Progress What are 3 differences between euk. and prokary. transcription?

Answer 5

1) euk mRNA is more stable
2) coupling of transcription & translation in prok (happen at the same time)
3) polycistronic mRNA (pro) vs single protein coding mRNA (euk)

Question 6

Which RNA polymerase makes mRNAs in eukaryotes?

Answer 6

RNA polymerase II

Question 7

What is the role of a promoter in transcription?

Answer 7

binds to RNA polymerase to start transcription and tells RNA polymerase II which direction to go

Question 8

What characterizes promoter sequences?

Answer 8

flexible and variable to regulate transcription
-tighter bond to polymerase–> increase transcription
-looser bond–> slower

Question 9

What are the consensus sequences for promoter sequences located in prokaryotes?

Answer 9

-35… -10 sequences upstream of +1 (transcription start)

Question 10

What are the 4 promoter sequences in eukaryotes?

Answer 10

1) TATA box
2) GC box
3) CAAT box
4) Octamer (OCT) box

Question 11

What strand is the promoter located on?

Answer 11

on the nontemplate strand (the coding strand)

Question 12

Define consensus sequence.

Answer 12

where on average specific sequences are found

Question 13

What are the consensus sequences for promoter sequences located in prokaryotes?

Answer 13

-90…-80…-25… +1

Question 14

How would a mutation in the consensus sequence affect transcription?

Answer 14

likely alter efficiency of promoter binding–> decrease gene transcription

Question 15

What is an enhancer?

Answer 15

in euk., increase the level of transcription, can be located upstream OR downstream of gene, can be really far (DNA bends)

Question 16

What is a silencer?

Answer 16

repress gene transcription by folding DNA to block gene transcription, can also be either up/downstream

Question 17

What are the 3 mechanisms that euk. use to increase the diversity of their proteins?

Answer 17

1) Alternative Splicing
2) Alternative Promoters
3) Alternative polyadenylation

Question 18

Define intron.

Answer 18

removed from DNA sequence

Question 19

Define exon.

Answer 19

coding region (kept in mature mRNA)

Question 20

Define alternative promoter.

Answer 20

able to initiate transcription at distinct start points (change +1) in diff. cell types

Question 21

Define alternative polyadenylation.

Answer 21

-addition of a Poly A tail to the 3’ end w/ cleavage –> mature mRNA

Question 22

Define alternative splicing.

Answer 22

allow for different variants of proteins w/o changing genotype by cutting out/turning off certain gene regions

Question 23

DNA polymerase vs. RNA polymerase

Answer 23

-replication vs transcription
-primer vs no primer
-both strands vs only template
-uses deoxy (-H) vs uses ribose (-OH)
BOTH: polyemerize 5’–> 3’