DNA structure and function

Question 1

people to know/their experiments

Answer 1

chargaff: found out a pairs with t and g to c
franklin: found out DNA is helical
watson/crick: made physical double helix model of DNA

Question 2

location of genetic info

Answer 2

nucleus and mitochondria

Question 3

purines and their shape

Answer 3

a (adenine) and g (guanine)
look like two double rings

Question 4

pyrimidines and their shape

Answer 4

t (thymine) c (cytosine) and u (uracil)
look like a single ring

Question 5

Nucleotides

Answer 5

a, t, g, c

Question 6

complementary bases

Answer 6

a, t, g, c are complement of each other via HYDROGEN BONDS

Question 7

in what way do DNA strands run

Answer 7

they run antiparallel 5’ to 3’ and are complementary to each other

Question 8

what is the template for DNA replication

Answer 8

the parent strand

Question 9

what is the daughter strand made of

Answer 9

it is made of the parent strand plus one new strand (the parent strand is the template for the new one)

Question 10

where does DNA replication start and what is formed

Answer 10

replication starts at the origin and two replication forks are formed (one on each side or origin)

Question 11

in what directions does DNA become copied

Answer 11

DNA is copied in both directions as they move away from the origin

Question 12

what direction is the DNA polymerase (long chain of atgc) read from

Answer 12

it reads the template strand from 3’ to 5’ and adds nucleotides in the 5’ to 3’ direction (done by hydrolysis)

Question 13

which strand is the leading strand and what does it mean

Answer 13

the 3’ to 5’ strand and is read continuously

Question 14

which strand is the lagging strand and what does it mean

Answer 14

the 5’ to 3’ strand is read discontinuously made in small pieces called Okazaki

Question 15

what does DNA polymerase do to avoid inaccurate copies of DNA

Answer 15

it checks for mistakes (proofreads) before moving on to prevent mutations

Question 16

primase

Answer 16

adds a primer (RNA fragment) to the template strand at the origin
ex: used as a makeup primer

Question 17

DNA ligase

Answer 17

joins Okazaki fragments to make a single DNA molecule

Question 18

helicase

Answer 18

separates DNA strands at origin

Question 19

topoisomerase

Answer 19

prevents DNA from being too coiled up

Question 20

single strand binding proteins

Answer 20

bind DNA so helix structure doesn’t reform

Question 21

DNA polymerase 1

Answer 21

replaces RNA primer with DNA
(this happens after primase job)

Question 22

what does the replication origin have a lot of

Answer 22

it’s rich in a and t because it is easier to break (less hydrogen bonds)

Question 23

telomeres

Answer 23

marks ends of chromosome and prevents loss of DNA during replication

Question 24

centromeres

Answer 24

allow duplicated chromosomes to be separated

Question 25

what are mispaired nucleotides called

Answer 25

a mismatch

Question 26

how do DNA repair enzymes fix a mismatch

Answer 26

they find the mismatched base and replace it with the correct one
Ex: a paired with g fixes to a paired with t

Question 27

what is nucleotide excision repair

Answer 27

it is the process of removing damaged bases

Question 28

what are the 3 steps in nucleotide excision repair

Answer 28

1. damage found and removed by nuclease
2. DNA polymerase makes copy from the template strand
3. DNA ligase fixes the damage in the backbone

Question 29

why does DNA damage happen

Answer 29

it happens because of chemical reactions in the cell (is spontaneous)

Question 30

silent point mutations

Answer 30

they cause NO CHANGE in the amino acid sequence

Question 31

missense point mutations

Answer 31

cause change in the amino acid sequence

Question 32

nonsense point mutations

Answer 32

STOPS the amino acid sequence leaving it short

Question 33

frameshift mutation

Answer 33

adds in or deletes a base pair causing the entire sequence to mess up