EXAM 2- Chapter 13/14

Question 1

RNA synthesis

Answer 1

all RNAs are synthesized in the nucleus
mRNA is exported to the cytoplasm and is translated
NTPs (riboNucleic TriPhosphates) are the building blocks of RNA

Question 2

DNA replication

Answer 2

high fidelity
once and only once per cell cycle
complete
requires RNA primer to start

Question 3

RNA Transcription

Answer 3

somewhat faithful (proofreading present but some errors occur)
not complete (only a set of genes transcribed at once)
occurs predominantly during G1/G2 phases
no primer required to start

Question 4

RNA structure

Answer 4

ribose sugar
thymine replaced by uracil
typically single-stranded primary structure
can form double stranded secondary structure
many classes of RNA in eukaryotes

Question 5

gene

Answer 5

any DNA sequence that is transcribed into RNA molecule

Question 6

RNA synthesis(2)

Answer 6

RNA Polymerase leads RNA production
RNA is complimentary and antiparallel to parent strand
non-template strand= coding strand
nucleotides are added to 3’ end of RNA molecule

Question 7

RNA synthesis steps

Answer 7

initiation of synthesis doesn’t require a primer
new nucleotides added to 3’ end of RNA molecule
DNA unwinds at the front of transcription bubble
then it re-winds

Question 8

promoter

Answer 8

highly conserved initial binding site of RNA polymerase
specifies which polymerase is used for the different classes of genes to be transcribed
upstream of RNA coding region

Question 9

3 major components of transcription

Answer 9

DNA template
raw materials to build new RNA molecule (NTPs)
transcription apparatus- contains proteins needed to catalyze RNA synthesis

Question 10

Basal transcription apparatus

Answer 10

contains general transcription factors and RNA polymerase
assembles near start site
sufficient to initiate minimal levels of transcription

Question 11

Pol2 promoter

Answer 11

consists of core and regulatory sequences

Question 12

core promoter

Answer 12

bound by basal transcription apparatus
immediately upstream of gene
one or more consensus sequence
contains TATA box, upstream of Start site

Question 13

regulatory promoter

Answer 13

immediately upstream of core promoter
variety of consensus sequences in different combinations
bound by transcription activator proteins- affect rate of transcription

Question 14

consensus sequence

Answer 14

comprised of the most commonly encountered nucleotides at each site
- pyrimidines indicated by Y
- purines indicated by R
- no base in common indicated by N
- / means two bases are equally common

Question 15

3 phases of transcription

Answer 15

initiation
elongation
termination

Question 16

Initiation

Answer 16

Transcription factors bind to TATA box and partially unwinds DNA
more transcription factors bind
Pol2 positioned over start site
transcription bubble formed
pol2 starts transcribing

Question 17

Elongation

Answer 17

trancription factor left behind on promoter
Pol2 moves along DNA template

Question 18

Termination

Answer 18

terminal sequence
Rat 1 (5’-3’ exonuclease) digest and recycles extra pieces that arent used

Question 19

Structure of mRNA

Answer 19

5’ methyl cap (post-translational mod)
5’ untranslated region
start codon
protein-coding region
stop codon
3’ untranslated region
poly A tail (post-translational mod)

Question 20

protein-coding region

Answer 20

series of nucleotides specifying the amino acids to be added

Question 21

5’ UTR

Answer 21

necessary for ribosome binding and intron splicing

Question 22

3’ UTR

Answer 22

regulatory role in mRNA stability and translation

Question 23

Steps of pre-mRNA processing

Answer 23

1. addition of 5’ methyl cap
2. polyadenylation (addition of poly A tail)
3. intron splicing

Question 24

addition of 5’ methyl cap

Answer 24

required to initiate translation
increases stability of mRNA
influences intron splicing
added during transcription

Question 25

polyadenylation

Answer 25

not coded in DNA (post-transcriptional mod.)
increase stability of mRNA
plays role in RNA export from nucleus
facilitates attachment of ribosome to mRNA
preceded by cleavage of 3’ downstream sequences

Question 26

Itron splicing

Answer 26

goal: stitch together all the exons of a gene and eliminate intron sequences
takes place in nucleus
carried out by large and complex molecular machinery (spliceosome)
consensus sequences necessary for correct splicing

Question 27

splicing introns in mRNA

Answer 27

cut and reform phosphodiester bonds
non-coding bases

Question 28

Alternative splicing

Answer 28

same gene produces identical pre-mRNA but are alternatively processed
important source of protein diversity in vertebrates
many human diseases arise from mutations that affect splicing