01/23 DNA as genetic material

Question 1

what is a negative control

Answer 1

in an experiment it is something that has no effect and acts as a consistent baseline

Question 2

what is a positive contorl

Answer 2

in an experiment, it is something that consistently shows an effect

Question 3

what is the purpose of controls

Answer 3

when using experimental groups, we can see/mimic the effect/no effect of the controls and they must be done everytime to serve as a baseline

Question 4

what were the controls in the Griffin Experiment

Answer 4

The rough strain was the negative control
- consistently had no effect
- no isolated bacteria were isolated from the mouse

The living smooth strain was the positive control
- consistently had an effect (killing the mouse)
- isolated smooth bacteria from the dead mouse

Question 5

what were the treatment groups in the griffin experiment

Answer 5

the heat killed smooth strain and the heat killed smooth strain + living R strain

Question 6

what treatment group emulated the positive control in the griffin experiment

Answer 6

the heat killed smooth strain + the living R strain killed the mouse and left isolated smooth bacteria

Question 7

what treatment group emulated the negative control in the griffin experiment

Answer 7

the heat killed smooth strain had no effect and no bacteria were found in the mouse

Question 8

how was the R strain and heat-killed S strain mixture able to kill the mouse

Answer 8

the R strain was somehow transformed by the hereditary material in the S strain

Question 9

what was the basis of the Avery, MacLeod, and McCarty Experiments

Answer 9

they wanted to know what was the transforming material (DNA, RNA, Protein, Carb, or Lipids)

Question 10

describe how the four criteria of genetic material were utilized in the transformation of the rough strains to smooth strains in griffins experiments

Answer 10

the bacterial cells acquired the “information” to make the capsule

“variation” existed in the ability to make a capsule

the information required to create a capsule is “replicated” and “transmitted” from mother and daughter cells

Question 11

In the Avery et al experiments, they used smooth cell extracts of DNA RNA or protein and introduced them to the rough strain. Were these extracts pure? Why or why not

Answer 11

No, these were not pure. They used rough cuts of enriched extracts for the samples, there was still some remnants of the other components in it

Question 12

in the Avery et al experiments, which smooth extract was able to transform the rough strain into the smooth strain

Answer 12

the enriched DNA extract

Question 13

what is in the extracts added to the R rough cells

Answer 13

DNA RNA and protein

Question 14

why do we add an antibody to the R+S extract mixture?

Answer 14

the antibody attaches to the rough cells that did NOT transform into smooth cells. This allows them to be centrifuged into a pellet and the subsequent supernatant liquid can be plated to grow smooth cells

Question 15

why do we add an enzyme to the extract mixture in the Avery experiment

Answer 15

the enzyme will destroy a targetted molecule (DNAase-> DNA, RNAase–> RNA, protease–> protein)

Question 16

the addition of which enzyme caused the treatment to emulate the negative control

Answer 16

DNAase, this revealed that DNA is the genetic material as the rough cells were not able to transform or grow smooth strains without the DNA

Question 17

Treatment with DNAase caused the destruction of genetic material which led to the inability to transform the rough strain into the smooth strain. When the sample was plated, the results looked like the negative control.

True or False

Answer 17

True

, when we treated with DNAase, the enzyme broke down the DNA molecules which contained the information necessary for the rough cells to undergo transform into the smooth cells. When we centrifuge the tubes, all of the rough cells will fall into the pellet and there would be no smooth cells in the supernatant to grow the resulting bacteria

Question 18

What is a bacteriophage comprised of

Answer 18

it is comprised of DNA and protein

Question 19

how does a bacteriophage function

Answer 19

it binds to specific binding proteins and injects its genetic material into the cell.

the genetic material hijacks the cells machinery and directs it to replicate the viral genome and proteins, resulting in the replication of more bacteriophages within the cell

the bacterium will be lysed (broken open) to release the newly formed phage progeny

Question 20

what was the hypothesis to the Hershey and Chase experiment

Answer 20

only the genetic material is injected and isotope labeling will reveal if it is DNA or protein

Question 21

What is a radioactive isotope? why is it used?

Answer 21

a radioactive isotope are atoms with unnatural amounts of neutrons that will decay and give off detectable alpha and beta particles

Question 22

in the Hershey and Chase experiment, why did they use P32 for DNA and S35 for protein ?

Answer 22

Phosphate is an essential part of DNA as it is the essential component of the phosphate backbone

Sulfer is most commonly found in protein and not DNA

Question 23

why would P32 not show up in the protein?

Answer 23

phosphorus is not native in protein but can be added later

Question 24

describe the first step in the Hershey experiment

Answer 24

radioactive P35 and S32 were placed into SEPARATE bacteria samples with bacteriophage, through replication the radioactive isotopes were incorporated into the proteins or DNA that make up the bacteriophage

Question 25

what was the second step of the Hershey experiment

Answer 25

the bacteriophage were removed from the samples and introduced into NEW Ecoli bacteria and allowed to incubate for a short period of time

Question 26

What is the attachement phase in the Hershey experiment

Answer 26

it is the short period of incubation where the radioactive phage's were allowed to bind an inject their genetic material into the cells

Question 27

After letting the bactereophage inject their genetic material, why did they blend the samples? (hershey exp)

Answer 27

they used to blender to sheer off the bacteriophage from the cells this allowed the "ghost" phage's to go into the supernatant liquid and the cells were centrifuged into a pellet

Question 28

If we didn't use the blender for the Hershey experiment, what would have happened to the radioactive results? where would P32 and S35 be?

Answer 28

if you do not use the blender, the phages will not be sheered off and all of the radioactivity will be in the pellet and NOT be detected in the supernatant this means the graph would be very low

Question 29

what does it mean when we call a bacterophage a "ghost"

Answer 29

it means it has delivered its genetic material into the cell

Question 30

When analyzing the results of the hershey experiment, what do we analyze? the pellet or the supernatant?

Answer 30

we are analyzing the supernatant with a scintillation counter which allows us to quantitatively count the radioactivity NOT IN THE CELL this is what was NOT injected into the cell

Question 31

if DNA is the genetic material, what results do we expect from the Hershey experiment

Answer 31

if DNA is the genetic material, we expect the majority of the P35 to be in the cell (low concentration in the supernatant)

Question 32

since protein is NOT the genetic material, where would be expect the S35 to be in the Hershey experiment?

Answer 32

we would expect it to be in the supernatant liquid. it was not injected into the cell, therefore it will remain on the outside and not be in the bacterial pellet

Question 33

what did the graph results from the Hershey experiment show?

Answer 33

it showed the % of radioactivity in the supernatant liquid. If the percentage was low, that means the remaining amount of radioactivity is in the pellet cell (was injected)

Question 34

why did the P32 sample not show 0% radioactivity for the supernatant

Answer 34

1) incomplete infection, - not all of the bacteriophages fully delivered their P32, some remains in the supernatant 2.) too light of centrifuging - if they vortexed it too hard, the cells would lyse and release everything but this means that not all of the phages may have been removed

Question 35

Why does the S35 test not show 100% concentration in the supernatant

Answer 35

the blender might not have been 100% effective, some of the bacteriophages with S35 may be attached and are in the pellet

Question 36

what was the overall result of the hershey experiment

Answer 36

since most of the S35 was in the supernatant and the majority of the P32 was in the pellet, this concludes that the P32 labeled DNA entered the bacteria and is the genetic material

Question 37

what happened when the bacteria were lysed to release the phage progeny from the prior labeled bactereopage?

Answer 37

the cells that were originally exposed to the P32 labeled phage released a new progeny of phage that were also radioactive the cells that were originally exposed to the S35 labeled phage released a new progeny of phage that were not radioactive since none of the radioactive labeled proteins entered the cell

Question 38

If it turned out that protein was the genetic material, then which of the following would be seen during Hershey and Chase's experiment? A. Radioactive sulfur would be seen primarily in the pellet and not in the supernatant B. Radioactive phosphorous would be seen primarily in the supernatant C. Radioactive sulfur would be seen in the bacteriophage that lyse out of the infected bacteria

Answer 38

A, B, C