unit 6 quiz 2 (6.3-6.4)

Question 1

steps of transcription

Answer 1

initiation, elongation, termination

Question 2

initiation for transcription

Answer 2

-transcription begins when RNA P mole attaches to a promoter region of DNA
-does not need primer to attach first
-promoter regions are before the desired gene to transcribe

euk
-promotor region is called the TATA box
-transcription factors help RNA P bind

prok
-RNA P can bind directly to promotor

Question 3

elongation (scription)

Answer 3

-RNA P opens the DNA and reads the triplet code of the template strand
-moves in a 3–>5
-adds in a 5–>3
-RNA P moves downstream and only opens small sections of DNA at a time
–>pairs complimentary RNA nucleotides

Question 4

termination (scription)

Answer 4

prok
-transcription proceeds through a termination sequence
-causes termination signal
-RNA P detaches
-mRNA transcript is released and proceeds to translation
–>mRNA doesnt need modifs

euk
-rna p transcribes a sequence of DNA called the polyadenylation signal sequence (AAUAAA)
-releases the pre-mRNA from the DNA
-must undergo modifs before translation

Question 5

pre-mRNA modif

Answer 5

1. 5’ cap
2. Poly-A tail
3. RNA splicing

Question 6

5’ cap

Answer 6

the 5 end of the pre-mRNA receives a modified guanine nucleotide “cap”

Question 7

poly a tail

Answer 7

the 3 end of the pre-mrna receives 50-250 adenine nucleotides

Question 8

both 5’ cap and poly a tail finction to

Answer 8

-help the mature mRNA leave the nucleus
-help protect the mRNA from degradation
-helps ribos attach to the 5 end of the mRNA when it reaches the cyto

Question 9

rna splicing

Answer 9

sections of the pre-mrna, called introns, are removed and then exons are joined together
- introns: intervening sequence, do not code for AA
- exons: expressed sections, code for AAs

a single gene can code for more than one kind of polypeptide, known as alternate splicing

Question 10

three steps of translation

Answer 10

1. initiation
2. elongation
3. termination

Question 11

initiation for translation

Answer 11

translation begins when the small ribosomal subunit binds to the mRNA and a charged tRNA binds to the start codon, aug, on the mRNA
-tRNA carries methionine
-next, the large subunit binds

Question 12

elongation (lation)

Answer 12

elongation starts when the trna comes into the A site
-mrna is moved through the ribo and its codons are read
-each mrna codon codes for a spec AA
-codon charts are used to determine the AA

1. codon recognition: appropriate anticodon of the next trna goes to the A site
2. peptide bond formation: formed that transfer the polypeptide to the A site tRNA
3. translocation: trna in the a site moves to the p site and goes to the e site. the a site is open for the next tRNA

Question 13

termination (lation)

Answer 13

termination occurs when a stop codon in the mRNA reaches the a site of the ribo
- stop codons singal for a release factor
–>hydrolyses the bonds that hold the polypeptide to the p site
-polypeptides release

Question 14

primary structure

Answer 14

linear chain of AA; dictates 2nd structure

Question 15

2nd structure

Answer 15

coils and folds due to h-bonding within the peptide backbone

Question 16

tertiary structure

Answer 16

side-chain interactions

Question 17

quaternary structure

Answer 17

2+ polypeptide chain interacting