DNA

Question 1

DNA

Answer 1

genetic material of all living organisms

Question 2

Griffith’s experiments

Answer 2

Transformation. Inject S- died, Inject R- live, inject dead S- live, inject dead S and live R- died

Question 3

Avery’s experiments

Answer 3

used bacteria instead of mice

• destroyed protein-still had transformation
• destroyed DNA- no transformation

Question 4

Hershey and Chase

Answer 4

used bacteriophage T2
used 35S and 32P to infect Ecoli (dna=P, protein=s)
infect bacteria, see if radioactivity ends up IN the cell

Question 5

Watson and Crick

Answer 5

discovered that a DNA molecule consists of two polynucleotide chains twisted around each other into a right handed double helix

Question 6

Each nucleotide consists of

Answer 6

1. deoxyribose
2. a phosphate group
3. a base

Question 7

Each full turn of double helix is…

Answer 7

10 base pairs

Question 8

Rosalind Franklin

Answer 8

used X-ray diffraction to discover the shape of DNA

Question 9

Semiconservative replication

Answer 9

two strands of parental DNA molecule unwind, each is a template for the synthesis of a complementary copy

Question 10

Meselson-Stahl

Answer 10

bacteria grown in 15N (heavy) then transferred to 14N and allowed to grow and divide for several generations. Then, centrifuge. Before it was all 15N, then 15N and 14N hybrid after 2nd, and 14-14, and 15-14 after 3, showing it kept one parent strand

Question 11

Helicase

Answer 11

unwinds the DNA

Question 12

Primase

Answer 12

synthesizes RNA primer (starting point for nucleotide assembly by DNA polymerases)

Question 13

DNA polymerases

Answer 13

assemble nucleotides into a chain (at 3’ end), remove primers, and fill resulting gaps

Question 14

DNA ligase

Answer 14

closes remaining single-chain nicks

Question 15

Single-stranded binding proteins

Answer 15

stabilize single-stranded DNA and prevent the two strands at the replication fork from reforming double stranded DNA

Question 16

Topoisomerase

Answer 16

avoids twisting of the DNA ahead of the replication fork (in circular DNA) by cutting the DNA, turning the DNA on one side of the break in the direction opposite to that of the twisting force, and rejoining the two strands

Question 17

DNA polymerase III

Answer 17

main replication enzyme in E.Coli; extends the RNA primer by adding DNA nucleotides to it

Question 18

DNA polymerase I

Answer 18

E.coli enzyme that uses it 5’ to 3’ exonuclease activity to remove the RNA of the previously synthesized Okazaki fragment, and uses its 5’ to 3’ polymerization activity to replace the RNA nucleotides with DNA nucleotides

Question 19

Sliding Clamp

Answer 19

tethers DNA polymerase III to the DNA template, making replication more efficient

Question 20

DNA synthesis

Answer 20

• begins at sites that act as replication origins
• only activated once during S phase
• proceeds from the origins as two replication forks moving in opposite directions

Question 21

Telomeres

Answer 21

• the ends of eukaryotic chromosomes
• short sequences repeated hundreds to thousands of times
• protects against chromosome shortening during replication

Question 22

Telomerase

Answer 22

enzyme that prevents chromosome shortening by adding telomere repeats

Question 23

Proofreading

Answer 23

if a replication error causes a base to be mispaired, DNA polymerase reverses and removes the most recently added base
-the enzyme then resumes DNA synthesis in the forward direction

Question 24

DNA repair mechanisms

Answer 24

1. Recognize
2. Remove
3. Resynthesize

Question 25

Recognize

Answer 25

distorted regions caused by mispaired base pairs

Question 26

Remove

Answer 26

mispaired base region from the newly synthesized nucleotide chain

Question 27

Resynthesize

Answer 27

correctly using original template chain as a guide