Ap Biology Unit 6

Front 1

DNA and protein

Back 1

What are the two chemical components of chromosomes?

Front 2

Biochemists had identified them as a class of macromolecules with great heterogeneity and specificity of function, essential requirements for the hereditary material. Nucleic Acids seemed too uniform.

Back 2

Why did researchers originally think that protein was the genetic material?

Front 3

There was a pathogenic strain and a nonpathogenic strain. The pathogenic strain turned some nonpathogenic pathogenic even when dead.

Back 3

Distinguish between the virulent and nonvirulent strains of Streptococcus pneumoniae studied by Frederick Griffith.

Front 4

To develop a vaccine against pneumonia

Back 4

What was the purpose of Griffith's studies?

Front 5

Back 5

Use this figure to summarize the experiment in which Griffith became aware that hereditary info could be transmitted between two organisms in an unusual manner.

Front 6

Transformation

Back 6

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

Front 7

DNA

Back 7

what did Oswald Avery determine to be the transforming factor?

Front 8

He broke open the heat-killed pathogenic bacteria amd extracted its contents. He inactivated DNA, RNA, and protein and tested each sample for its ability to transform live nonpathogenic bacteria.

Back 8

Explain Oswald Avery's experimental approach.

Front 9

Back 9

Sketch a T2 bacteriophage and label its head, tail sheath, tail fiber, and DNA.

Front 10

Phage genes enter the host cell and code for an enzyme that degrades the host's DNA.

Back 10

How does a bacteriophage destroy a bacterial cell?

Front 11

Sulfur- Protein bc protein contains sulfur.

Phosphorus- DNA bc DNA contains Phosphorus

Back 11

How did Hershey and Chase "label" viral DNA and viral protein so that they could be distinguished? Explain why they chose each radioactive tag in light of the chemical composition of DNA and protein.

Front 12

They tagged DNA and protein and allowed the phages to infect E. Coli. They then tested the samples to see which molecule had entered the cells. DNA injected by phages must be the molecule carrying the genetic information that makes cells produce new viral DNA and proteins.

Back 12

Describe the means by which Hershey and Chase established that only the DNA of a phage enters an E. Coli cell. What conclusions did these scientists draw based on these observations?

Front 13

1. The base composition of DNA varies from one species to another.

2. The Number of adenines= the number of thymines and the number of cytosines= the number of guanines.

3. All species contain adenine, thymine, cytosine, and guanine.

Back 13

What are Chargaff's rules?

Front 14

He analyzed the base composition of DNA from a number of different organisms.

Back 14

How did Chargaff arrive at his rules?

Front 15

nitrogenous base, deoxyribose, and phosphate group

Back 15

List the components of a nucleotide

Front 16

Watson and Crick

Back 16

Who built the first model of DNA and shared the 1962 nobel Prize for discovery of its structure?

Front 17

She produced an xray diffraction image of DNA through xray crystallography. She came up with the double helix shape with sugar phosphates on the outside. She came up with the details that allowed watson and crick to build thei model.

Back 17

What was the role of Rosalind Franklin in the discovery of the double helix?

Front 18

Purines have two organic rings, pyramidines have one.

Because one is a purine and the other is a pyramidine, together they are the perfect length.

Back 18

Distinguish between the structure of pyramidines and purines. Explain why adenine bonds only to thymine.

Front 19

It showed that only A partners with T and only G with C. It helped explain why by showing how they fit together.

Back 19

How did Watson and Crick's model explain the basis for Chargaff's rules?

Front 20

Back 20

Name the 5 nitrogenous bases.

Front 21

A pairs with T. G pairs with C.

Back 21

Explain the base pairing rule.

Front 22

1nm

.34 nm

3.4 nm

sugar and phosphate

nitrogenous bases

Back 22

Describe the structure of DNA relative to each of the following.

Distance across molecule

distance between nucleotides

distance between turns

components of the backbone

components of the "rungs"

Front 23

The numbers assigned to the carbons in the sugar ring

Back 23

Explain what is meant by the 5' and 3' ends of the nucleotide.

Front 24

The 5' end matches up with another's 3' end.

Back 24

What do we mean when we say the two strands of DNA are antiparallel?

Front 25

When a double helix replicates, each of the two new daughter molecules will have one old strand, derived from the parent molecule and one newly made strand.

Back 25

What is the semiconservative model of replication?

Front 26

Matthew Meselson and Franklin Stahl

Back 26

Who performed the experimenrs that elucidated the correct mechanism of DNA replication?

Front 27

They cultured the bacteria in a heavy isotope and then put them in a lighter isotope

Back 27

How did Meselson and Stahl create "heavy" DNA for their experiments?

Front 28

The bacteria was cultured in 15N and then transferred to medium containing 14N. Then the DNA was centrifuged after 20 and 40 min. They got light and hybrid DNA, proving the semiconservative model.

Back 28

Use this to explain how Meselson and Stahl confirmed the semiconservative mechanism of DNA replication.

Front 29

origins of replication

Back 29

Short stretches of DNA having a specific sequence of nucleotides; Where replication begins.

Front 30

The leading strand is the DNA strand made by DNA pol III nesting in the replication fork and adding nucleotides. 5'-3' direction.

The lagging strand is the strand created as DNA Pol III works away from the template.

Back 30

Distinguish between the leading and lagging strands during DNA replication.

Front 31

5'-3'

Back 31

What is the direction of synthesis of the new strand?

Front 32

Segments of the lagging strand.

Using DNA Pol I.

Back 32

What are Okazaki fragments? How are they welded together?

Front 33

Helicase

Back 33

Which enzyme untwists and separates strands?

Front 34

single stranded binding proteins

Back 34

Which enzyme holds DNA strands apart?

Front 35

primase

Back 35

Which enzyme synthesizes RNA primer

Front 36

DNA polymerase III

Back 36

Which enzyme adds DNA nucleotides to new strand?

Front 37

Topoisomerase

Back 37

Which enzyme relieves strain caused by unwinding?

Front 38

DNA Ligase

Back 38

Which enzyme joins DNA fragments together?

Front 39

DNA Pol I

Back 39

Which enzyme removes RNA primer and replaces with DNA

Front 40

Back 40

Look at the following figures of replication

Front 41

1. primase joins RNA nucleotides into a primer.

2. DNA pol III adds DNA nucleotides to the primer, forming okazaki fragment I.

3. After reaching the next RNA primer to the right, DNA pol III detaches.

4. After fragment 2 is primed, DNA pol III adds DNA nucleotides until it reaches the fragment I primer and detaches.

5. DNA pol I replaces the RNA with DNA, adding to the 3' end of fragment 2.

6. DNA ligase forms a bind between the newest DNA and the DNA of fragment I.

7. The lagging strand in this region is now complete.

Back 41

Make a detailed list of the steps that occur in the synthesis of a new strand.

Front 42

It proofs each nucleotide against its template and removes mistakes. Helps fill in gap left by nuclease

Back 42

Explain the roles of DNA Polymerase in DNA proofreading and repair.

Front 43

cuts out the damaged strand of DNA

Back 43

Explain the role of Nuclease in DNA proofreading and repair.

Front 44

it fills in the gap left by nuclease with nucleotides

Back 44

explain the role of ligase in DNA proofreading and repair.

Front 45

it repairs genetic damage caused by ultraviolet rays of sunlight

Back 45

explain the role of repair enzymes in DNA proofreading and repair

Front 46

The covalent linking of thymine bases that are adjacent on a DNA strand. Causes the DNA to buckle and interfere with DNA replication.

Damage by UV rays

Repaired by DNA repair enzymes in our skin cells.

Back 46

What is a thymine dimer? How might it occur? How is it repaired?

Front 47

Back 47

Look at the telomeres

Front 48

Telomeres become shorter during every round of replication

Back 48

Explain telomere erosion

Front 49

Telomerase catalyzes the lengthening of telomeres in eukaryotic germ cells, restoring their length, compensating for shortening

Back 49

Explain the role of telomerase

Front 50

They have unlimited cell division and telomerase activity. Telomerase is not active in body cells

Back 50

Why are cancer cells immortal but most body cells have a limited life span?

Front 51

Back 51

Front 52

Heterochromatin- Interphase chromatin visible as irregular clumps with a light microscope. less accessible.

Euchromatin- Less compacted, more dispersed. DNA is accessible to cell machinery so its genes can be expressed.

Back 52

Distinguish between heterochromatin and euchromatin.

Front 53

c

Back 53

In his work with pneumonia-causing bacteria and mice, Griffith found that

a. the protein coat from pathogenic cells was able to transform nonpathogenic cells

b. heat killed pathogenic cells caused pneumonia

c. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic

d. the polysaccaride coat of bacteria caused pneumonia

e. bacteriophages injected DNA into bacteria

Front 54

d

Back 54

E. Coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

a. one high density and one low density band

b. one intermediate density band

c. one high density and one intermediate density band

d. one low density and one intermediate density band

e. one low density band

Front 55

b

Back 55

A biochemist isolates and purifies molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

a. DNA polymerase

b. DNA ligase

c. nucleotides

d. okazaki fragments

e. primase

Front 56

c

Back 56

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

a. the origins of replication occur only at the 5' end

b. helicases and single strand binding proteins work at the 5' end.

c. dna polymerase can join new nucleotides only to the 3' end of a growing strand

d. dna ligase works only in the 3'-5' direction

e. polymerase can work on only one strand at a time

Front 57

b

Back 57

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base paring rules?

a. A=G

b. A+G=C+T

c. A+T=G+T

d. A=C

e. G=T

Front 58

d

Back 58

The elongation of the leading strand during DNA synthesis

a. progresses away from the replication fork

b. occurs in the 3'-5' direction

c. produces okazaki fragments

d. depends on the action of DNA polymerase

e. does not require a template strand

Front 59

a

Back 59

The spontaneous loss of amino groups from adenine results in hypoxanthine, an uncommon base, opposite thymine in DNA. What combination of molecules could repair such damage?

a. nuclease, DNA polymerase, dna ligase

b. telomerase, primase, and dna polymerase

c. telomerase, helicase, single strand binding protein

d. dna ligase, replication fork proteins, adenylyl cyclase

e. nuclease, telomerase, primase

Front 60

c

Back 60

In a nucleosome, the DNA is wrapped around

a. polymerase molecules

b. ribosomes

c. histones

d. a thymine dimer

e. satellite dna