Lecture 6 Flashcards Preview

Biochemistry > Lecture 6 > Flashcards

Flashcards in Lecture 6 Deck (26)
Loading flashcards...
1

What does DNA store?

DNA is a stable storage form of genetic information

2

Is DNA static?

NO- DNA metabolism includes replication, repair, and recombination

3

What is the most important requirement of DNA metabolism?

Accuracy- if you change the blueprint, you change the causing sequence, changing the protein structure/function

4

Why are repair mechanisms required?

Multiple damaging reactions can and do occur

5

RNA has a 2' hydroxyl group which could deprotenate and do what...

It makes the oxianion a nucleophile right in proximity with an electrophile and it hydrolyzes the phosphodiester backbone in RNA.
-Eventually RNA degrades itself bc of nucleophile

6

Evolution has made which one more stable? DNA vs. RNA

DNA-more stable storage form to store information than RNA

7

Bacterial Genes are written in...

lower case italics, usually 3 letters (ispA, ispB)

8

Proteins are usually written in...

Roman type and first letter is capitalized (IspA, ISPB)

9

What makes accurate replication of genetic material possible?

Specific pairing of DNA bases

10

Semiconservative

DNA is semiconservative because each strand can act as a template for the synthesis of a perfect copy of the other strand

11

DNA polymerases

Enzymes responsible for replication. Polymerize 5'->3'

12

Template Runs from...

3'->5"

13

Phosphate Atoms during DNA replication

DNA Catalyzes nucleophillic attack.
-Oxygen acts as a nucleophile
-Attacks the ALPHA phosphorous atom and make phosphate be the leaving group
-Phosphodiester bond forms
-Polymerase CANNOT continue on (DNTP)
-Can be hydrolyzed by inorganic phophotase to thermodynamically make favorable

14

Meselson and Stahl Hypothesis

Each new DNA molecule consists of one old strand and one new strand

15

Meselson and Stahl Grew E.coli Cells in...

15N labeled NH4CL and determed the DNA density.

16

Meselson & Stahls Experiment

After groing e.coli in 15N NH4CL
-moved cells to media with 14N NH4Cl and let them double once
-Isolated DNA was lighter
-After second doubling, they showed there were 2 bands of DNA- confirming semi conservative DNA.

17

Ultracentrifugation

Meselson-Stahl Experiment:
-set up in salt gradient
-set up a density gradient and ended up with not very dense at top and dense at bottom
-Put DNA at top and spun it

18

DNA Polymerase uses...

Single strand DNA templates and adds nucleotides to a growing chain in the 5'-3' direction

19

Replication bubbles suggest that...

theres a seperation of 2 strands of DNA acompanied by synthesis of complementary strand
*important for lucidation of DNA replications- A-T rich origin replication because easier to break.

20

Origin of Replication

Replication always begins at this unique point

21

Replication Fork

-Branch point in a replication bubble
-Bidirectional

22

DNA Polymerases work in what direction?

5' to 3"

23

During Polymerization, the new DNA base is added to...

the 3' OH of the previous added base

24

Evidence suggests that both strands of DNA are replicated...

Simultaneously- which is a problem because this means both strands cannot be synthesized continuously

25

Semidiscontnuous Replication model

-Leading Strand is continuously synthesized in the 5' to 3' direction.
-Lagging Strand is synthesized in the 5' to 3' direction in a
DISCONTINUOUS manner

*3' OH is nucleophile dictating the direction

26

DNA Ligase

Required to join the discontinuous Okazaki Fragments together into a continuous piece of DNA