History of DNA

Question 1

Who discovered substance in nuclei

Answer 1

miescher

Question 2

Who identified components on nucleotides

Answer 2

levene

Question 3

suggested a transforming factor existed to change bacteria from one strain to another

Answer 3

griffith

Question 4

Who found that dna is genetic material

Answer 4

Avery-MacLeod-McCarty

Question 5

Who Confirmed DNA as

genetic material

Answer 5

Hershey-Chase

Question 6

Who discovered DNA Double helix

model

Answer 6

Franklin, Watson and

Crick

Question 7

Who discovered
Semi-conservative
DNA replication

Answer 7

Meselson-Stahl

Question 8

Who Deciphered the Genetic Code

Answer 8

Khorana, Holley, and

Nirenberg

Question 9

Chromatin

Answer 9

DNA and its associated proteins

Question 10

Replication origin

Answer 10

site where DNA duplication begins.

Question 11

Centromere

Answer 11

Holds 2 chromosomes together to make sure each cell will get one copy during cell division

Question 12

Telomere

Answer 12

Contains repeated nucleotide sequences required for proper replication and protects the ends of the chromosomes

Question 13

Interphase vs. Mitotic Chromosomes

Answer 13

Mitotic: Two condensed chromosomes.

Interphase: Decondensed DNA

Question 14

Function of histones

Answer 14

Associate with DNA, forming chromatin and promote chromosomes packing via nucleosomes

Question 15

What are nucleosomes

Answer 15

composed of histones and DNA held together by noncovalent interactions.

Question 16

how does histone acetylation affect packing

Answer 16

more acetylation causes less packing, more deacetylation causes more packing.

Question 17

Heterochromatin vs. Euchromatin

Answer 17

• Heterochromatin: Highly condensed DNA, enriched at
centromeres and telomeres. Contains very few genes,
and those genes contained within heterochromatin are
usually turned off.
• Euchromatin: Less condensed DNA

Question 18

function of dna helicase

Answer 18

unwinds the double helix, using energy from ATP

Question 19

Single-strand DNA-binding proteins

Answer 19

stabilize single-stranded DNA

Question 20

DNA Topoisomerases

Answer 20

Enzymes that allow rotation of the helix to relieve strain during DNA replication. • Prevents tangling of the DNA.

Question 21

DNA Primase

Answer 21

synthesizes RNA primers for initiation of DNA replication.

• RNA Primers serve as a red flag to ensure extra proofreading of these fragments, provides 3’OH site for DNA synthesis.

Question 22

Clamp loader

Answer 22

helps load the sliding clamp onto the DNA
DNA Polymerase associates with the clamp
Sliding clamp keeps DNA Polymerase on the DNA until it runs into double stranded DNA and falls off.

Question 23

Lagging Strand Synthesis

Answer 23

• Synthesis of lagging strand stops
when it runs into the 5’ end of
another fragment.
• RNA primer is degraded.
• Sequence filled in by DNA
Polymerase.

Question 24

DNA Ligase

Answer 24

• Enzyme that joins the 3’ end of one fragment to the 5’ end of another Okazaki fragment. • Uses one molecule of ATP to catalyze this otherwise unfavorable sealing reaction.

Question 25

describe 3 to 5 exonuclease proofreading activity

Answer 25

Incorrect nucleotide pair is cut out by DNA polymerase

Question 26

Why can’t dna synthesis occur in opposite direction?

Answer 26

If synthesis occurs in the 3 to 5 direction, polymerization can’t proceed due to there being no high energy bond to drive the reaction.

In the 5 to 3 direction, the open 3’ OH allows for the high energy bond to be cleaved, providing energy for polymerization.

Question 27

What is the function of telomerase?

Answer 27

Replenishes end sequences of chromosomes, contains bound RNA template.
Telomerase binds to template strand and adds additional telomere repeats to it. Then DNA polymerase completes the lagging strand.