ch 6

Question 1

what were the findings of Griffiths’s experiment?

Answer 1

injected rats with different variations of disease and concluded there must be an unknown heritable substance

Question 2

Hershey and chase

Answer 2

-demonstrated that DNA is the genetic material of the T2 bacteriophage
- ran two experiments and grew them into a phosphorus medium for DNA and sulfur for Protein.
= They were both radioactive elements that could be seen in the cell and they were able to determine that the DNA was present inside the host

Question 3

Chargaff rules

Answer 3

-Base composition of DNA varies between species
-In any species the number of A and T bases are equal and the number of G and C bases are equal

Question 4

Origin of replication

Answer 4

• DNA strands are separated forming a replication bubble (EUK have a bunch of these) and in these sites replication happens in both directions (bidirection)

Question 5

what kind of DNA do prokaryotes and Eukaryotes have? amount of OR?

Answer 5

-p: circular / 1 in the cytoplasm
-E: linear/many in the nucleus

Question 6

Helicase

Answer 6

-enzymes that untwost the double helix at the replication fork
Like a scalpel

Question 7

Single stranded biding proteins:

Answer 7

-binds to and stabilizes single-stranded DNA after helicase
DNa doesnt like to be single stranded there like clamps holding it open

Question 8

Topoisomerase

Answer 8

corrects overwinding ahead of replication forks by breaking, swiveiling and rejoin DNA

Question 9

Replication initiation

Answer 9

-primase : starts an RNA chain from scratch and adds RNA nucleotides one at a time using the parental strand DNA as template to make a primer
-DNA polymerase: catalyzes the elongation of new DNA at the replication fork

Question 10

what does DNA pol need to bind?

Answer 10

-primer and DNA template with a free 3’ OH group

Question 11

DNA pol direction that it adds in

Answer 11

5 to 3

Question 12

How long would it take for DNA replicate the entire genome of an organism? In a eukaryotic organism with 1 million base pairs and 500 origins of replications and 50 nucleotides?

Answer 12

Goes in a bi-deirectional mannar
50 nucleotides (in 1 direction) x 2(bi-directional) = 100 nuc per sec in both directions
100 nucs/sec x 500 OR= 50000 nuc/sec
1,000,000 nucs to work through/50,000 nuc/sec = 20 secs (fast adn accurate)

Question 13

what are leading strands?

Answer 13

DNA polymerase 3 synthesizes a leading strand continuously moving toward the replication fork

Question 14

what are lagging strands? what can they lead to? fixed?

Answer 14

-DNA polymerase 3 synthesizes the lagging strand away from the replication fork in a series of segments called Okazaki fragments
- joined by DNA ligase: an enzyme that joins fragments together to make one continuous strand

Question 15

what can DNA pol not do?

Answer 15

-cannot synthesize new strands; they can only add to the 3’ end of the existing strand

Question 16

what are telomeres?

Answer 16

-Telomere a special nucleotide sequence at the end of the eukaryotic chromosomes - cant prevent shortening but can postpone erosion of chromosome ends

Question 17

whats telomerase? which cells are they active in

Answer 17

-an enzyme that maintains telomere length/lengthens telomere
-Active in germ cells (gametes) and in some cancer cells (making them immortal) and Inactive in somatic cells

Question 18

do eukaryotes or prokaryotes use telomeres?

Answer 18

-Euk needs these because their DNA is linear unlinked prok who don’t need it since their DNA is circular

Question 19

what are the three types of tetrads?

Answer 19

tetratypes (T): 2 parental and 2 recombos - caused by crossing over
-parental (pd)
-nonparental(NPD)
PD»T»NPD

Question 20

what does a heteroduplex cause?

Answer 20

• caused by gene conversion which is mistmatch repair of 2 alleles
  -creates a 3:1 ratio