DNA Replication & RNA Structure/Function

Question 1

What are the 3 proprosed models of DNA Replication Mechanism?

Answer 1

1. Dispersive: breakage and reunion
2. Semiconservative: unwind and replicate each
3. Conservative: replication without unwinding

SEMICONSERVATIVE IS HOW IT ACTUALLY DOES IT

Question 2

DNA is synthesized in what direction?

Answer 2

5’ to 3’

Question 3

What are the 5 components required for synthesis of DNA?

Answer 3

1. All four dNTPs (AT,GC)
2. A fragment of DNA to act as a template
3. DNA polymerase
4. Mg 2+ (cofactor for DNA polymerase activity)
5. A primer providing free 3’-OH group

Question 4

What is the role of DNA polymerase?

Answer 4

1. Catalyzes formation of phosphodiester bond between 3’ OH group and 5’ phosphate
2. Needs a primer before it can start
3. At each step is forms the complementary base on the template strande
4. If it makes a mistake-it can repair it
5. 3’ to 5’ proofreading exonuclease activity of DNA polymerase- clips off any unpaired residues

Question 5

Function of DNA polymerase III?

Prokaryotic

Answer 5

Primary enzyme of DNA synthesis

Alpha subunit

Question 6

DNA synthesis on the lagging strand is…?

3 steps

Answer 6

Discontinuous.
Has a series of short segments known as Okazaki fragments
1. DNA polymerase III synthesizes the Okazaki fragment
2. DNA polymerase I removes the RNA primer
3. DNA ligase joins the DNA gragments together (phosphodiester bond)

Question 7

Helicase function

Answer 7

Unwinds helix

Question 8

Single strand binding proteins

Answer 8

Prevent reattachment of original DNA strands

Question 9

Primase function

Answer 9

Initiates attachment of new polynucleotide strand

Question 10

DNA polymerase I function

Answer 10

Replacement of RNA primer with DNA

Question 11

Ligase function

Answer 11

Joins Okazaki fragments of lagging strand

Question 12

Topoisomerase function

Answer 12

Severs over-wound DNA then reattaches it

This is due to stress-it removes it

Question 13

2 main differences between DNA synthesis and RNA synthesis?

Answer 13

1. No primer needed for RNA
2. Uracil instead of thymine in RNA

Question 14

What are the three stages of transcription?

Answer 14

1. Initiation
2. Elongation
3. Termination

Question 15

The DNA sequence where RNA polymerase attaches to is called?

Answer 15

The promotor

Question 16

What are the alterations of mRNA?

Answer 16

1. 5’ prime end receives a 5’ cap
2. 3’ end receives a poly A tail
3. Excision of introns

Protect them from hydrolytic enzymes, help ribosomes attach

Question 17

What removes introns?

Answer 17

RNA splicing (by spliceosomes)

Question 18

Can 1 mRNA give rise to more than one protein?

Answer 18

YES, think about tropomyosin gene

Question 19

What is RNA polymerase in bacteria composed of?

Answer 19

Core polymerase and sigma factor

Question 20

RNA polymerase in eukaryotes (3)

Answer 20

1. 5.8S, 18S, 28S
2. All protein-coding genes (mRNA) and some snRNAs
3. tRNA genes and some snRNAs

Question 21

Eukaryotic promotors (5)

Answer 21

1. GC Box
2. CAAT Box
   **3. BRE
3. TATA Box
4. INR (initiator element)**

Bolded=core promotor

Question 22

What does polycistrionic mean?

Answer 22

Can code for multiple proteins

Question 23

Can RNA be edited after the final transcipt?

Answer 23

Yes-
Substitution ending
Insertion/deletion

Question 24

What is the structure of tRNA?

Answer 24

Hydrogen bonds in between base pairs
Looks like a cloverleaf

Question 25

What are the acidic amino acids?

Answer 25

1. Aspartic acid
2. Glutamic acid

Question 26

What are the neutral nonpolar amino acids?

Answer 26

1. Tryptophan
2. Phenylalanine
3. Glycine
4. Alanine
5. Valine
6. Isoleucine
7. Leucine
8. Methionine
9. Proline
   10.

Question 27

What are the basic amino acids?

Answer 27

1. Lysine
2. Arginine
3. Histidine

Question 28

What are the neutral polar amino acids?

Answer 28

1. Tryosine
2. Serine
3. Threonine
4. Asparagine
5. Glutamine
6. Cysteine

Question 29

What terminal do amino acids start from?

Answer 29

N to C terminus