LO12

Question 1

Describe Griffith’s experiment.

Answer 1

Showed that some material could be transferred from disease-causing bacterial strains (S cells) to non infected strains (R cells) which transformed the R cells into S cells

Question 2

What was the contribution of Avery and his colleagues to Griffith’s experiment?

Answer 2

Showed that the transforming material was DNA

Question 3

Griffith’s and Avery’s work showed that DNA was the genetic material in which group of organisms?

Answer 3

prokaryotes (bacteria)

Question 4

What did Hershey and Chase’s experiment show?

Answer 4

That DNA was the genetic materials in bacteriophages

Question 5

definition: viruses that infect bacteria

Answer 5

bacteriophages

Question 6

How did Hershey and Chase demonstrate that DNA was the genetic material and not proteins?

Answer 6

They radioactively labelled both the proteins and DNA to which entered the bacteria cells

Question 7

Watson and Crick proposed what model of DNA?

Answer 7

Double helix model of DNA

Question 8

What was Watson and Cricks model based on?

Answer 8

Rosalind Franklin’s X-ray diffraction images of DNA

Question 9

What is X-ray diffraction used for?

Answer 9

to determine the distance between atoms in a molecule

Question 10

Watson, Crick, and Maurice Wilkins won what?

Answer 10

The nobel prize for discovering the structure of DNA

Question 11

What was initially wrong with Watson and Crick’s first model of DNA?

Answer 11

They placed the bases on the outside and the sugar-phosphate backbone on the inside

Question 12

Meselson and Stahl confirmed what?

Answer 12

The semiconservative mode of replication

Question 13

What was Meselson and Stahl’s experiment?

Answer 13

They used different N isotopes to show that the double helix produced had one parent strand and a new daughter strand

Question 14

What monomers make up a single strand of DNA?

Answer 14

adenine, thymine, cytosine, guanine

Question 15

What are the three parts of a monomer?

Answer 15

pentose sugar, phosphate group, nitrogenous base

Question 16

What are the two purine bases?

Answer 16

adenine and guanine

Question 17

What are the two pyrimidine bases?

Answer 17

cytosine and thymine

Question 18

What is the 1’ Carbon connected to?

Answer 18

nitrogenous base

Question 19

What is the 2’ Carbon connected to?

Answer 19

hydroxyl group

Question 20

What is the 3’ Carbon connected to?

Answer 20

-OH group

Question 21

What is the 5’ Carbon connected to?

Answer 21

Phosphate group

Question 22

What is found at the 5’ end of a DNA molecule?

Answer 22

exposed phosphate group

Question 23

What is found at the 3’ end of a DNA molecule?

Answer 23

exposed -OH group

Question 24

What is the name of the bond joins nucleotides together in a single strand?

Answer 24

phosphodiester bond

Question 25

What type of bond is a phosphodiester bond?

Answer 25

covalent bond

Question 26

Where does the phosphodiester bond form?

Answer 26

3' Carbon of one sugar molecule and 5' Carbon of another

Question 27

What bond forms the double helix?

Answer 27

hydrogen bonds

Question 28

DNA strands are what?

Answer 28

antiparallel and complementary

Question 29

What does antiparallel mean?

Answer 29

One strand is 5-->3 and the other is 3-->5

Question 30

Cargaff determined what?

Answer 30

base pair rules

Question 31

Adenine and Thymine are joined by how many hydrogen bonds?

Answer 31

2

Question 32

Cytosine and Guanine are joined by how many hydrogen bonds?

Answer 32

3 bonds

Question 33

definition: breaks down hydrogen bonds at one or more origins of replication

Answer 33

DNA helicase

Question 34

definition: stabilizes unwound DNA and prevents reforming of hydrogen bonds and DNA from being degraded

Answer 34

Single-strand binding proteins (SSB)

Question 35

definition: relieves tension as DNA is unwound

Answer 35

Topoisomerase

Question 36

Which enzyme forms replication forks?

Answer 36

DNA helicase

Question 37

What does it mean for DNA replication to be bidirectional?

Answer 37

The process of replication happens at the same time in opp directions

Question 38

How many replication forks are formed at each origin of replication?

Answer 38

two

Question 39

definition: break and rejoin DNA strand to prevent supercoiling

Answer 39

topoisomerases

Question 40

What enzyme begins replication?

Answer 40

DNA helicase

Question 41

definition: enzyme that uses parent strand as a template and adds nucleotides to form daughter strand

Answer 41

DNA polymerase

Question 42

What are DNA ploymerases limitations?

Answer 42

- Can only add nucleotides to 3' end - Can't add first nucleotide of a new daughter

Question 43

definition: makes a complementary RNA primer at each origin of replication

Answer 43

DNA primase

Question 44

DNA polymerase replicates in what direction?

Answer 44

5-->3

Question 45

definition: daughter strand that is synthesized continously

Answer 45

leading strand

Question 46

In what direction is the leading strand synthesized?

Answer 46

Towards the replication fork

Question 47

Where is a single RNA primer synthesized?

Answer 47

At the origin of each leading strand

Question 48

What is the RNA primer synthesized by?

Answer 48

DNA primase

Question 48

How many RNA primers will by synthesized by DNA primase for the leading strand?

Answer 48

one

Question 48

definition: short pieces of the lagging strand

Answer 48

okazaki fragments

Question 48

definition: the daughter strand synthesized away from the replication fork

Answer 48

lagging strand

Question 48

What bond does DNA ligase use to link okazaki fragments?

Answer 48

phosphodiester bonds

Question 48

Lagging strand is synthesized in what direction?

Answer 48

5-->3

Question 48

What are the roles of DNA polymerases during lagging strand?

Answer 48

- adds nucleotides to 3' end - degrades RNA primer and replaces with nucleotides

Question 48

definition: links adjacent okazaki fragments

Answer 48

DNA ligase

Question 48

definition: enzyme that proofreads as it synthesizes each new daughter strand

Answer 48

DNA polymerase

Question 48

How many points of origin does prokaryotic chromosomes have?

Answer 48

only one

Question 49

How many points of origin does eukaryotic chromosomes have?

Answer 49

multiple origins of replication

Question 50

When would a cell use mismatch repaired?

Answer 50

When DNA. has been incorrectly paired

Question 51

When would a cell use nucleotide excision repair?

Answer 51

When DNA has been damaged by UV radiation or carcinogens

Question 52

What do nucleases do in the DNA proofreading and repair process?

Answer 52

cuts out DNA

Question 53

What does DNA polymerase do in the DNA proofreading and repair process?

Answer 53

it adds the correct nucleotides

Question 54

What does DNA Ligase do in the DNA proofreading and repair process?

Answer 54

It links the new pieces of DNA with phosphodiester bonds

Question 55

definition: repair that cuts out DNA that has been incorrectly paired

Answer 55

mismatch repair

Question 56

definition: cuts out DNA that has been damaged by UV radiation or carcinogens

Answer 56

Nucleotide excision repair

Question 57

A small portion at the end of each linear chromosomes cannot be what?

Answer 57

replicated

Question 58

Why can a small part at the end of a chromosome not be replicated?

Answer 58

limitation of DNA polymerase - cant replace RNA primer at 5' end

Question 59

What happens to the RNA primer at the end of replication?

Answer 59

it is eventually degraded

Question 60

What happens to chromosomes at the end of each cell cycle?

Answer 60

they shorten sligtly

Question 61

definition: short, noncoding, repetitive DNA sequences at the end of chromosomes

Answer 61

telomeres

Question 62

What does telomerase do?

Answer 62

extends length of chromosomes by adding telomere sequences

Question 63

Telomerase is active in what kind of cells?

Answer 63

Ones that have unlimited cell division

Question 64

definition: cells that have unlimited cell division

Answer 64

epithelial stem cells

Question 65

What relates to telomere shortening?

Answer 65

cell aging and apoptosis

Question 66

Why do cells lose their ability to divide?

Answer 66

Because telomeres get too short

Question 67

Henry and Chase radioactively labelled the DNA with what?

Answer 67

phosphorus

Question 68

Henry and Chase radioactively labelled the proteins with what?

Answer 68

sulfur

Question 69

What is the sugar phosphate backbone of DNA formed by

Answer 69

phosphate groups, phosphodiester linkages, deoxyribose sugars, covalent bonds