1. Scientist Frederick Griffith performed an experiment in 1928 in which harmless pneumococcal

bacteria were changed into a deadly strain by what Griffith identified as a “transforming principle.”

The results of the Griffith experiment are shown in the diagram below.

In 1944, scientists Oswald Avery, Colin MacLeod, and Maclyn McCarty were able to isolate the

“transforming principle” and test it. Chemical analysis showed that the compound contained

carbon, hydrogen, nitrogen, and phosphorus. The scientists then exposed the compound to

several hydrolytic enzymes. The results of the scientists’ experiment are shown in the table

below.

 

3.4 B: DNA is the Heritable Material Quiz

8Page 1 of

PROCTOR VERSION

 

Which statement best describes how the result of the Avery-MacLeod-McCarty experiment

provided insight into the observation made in the Griffith experiment?

(A) The results of the Avery-MacLeod-McCarty experiment show that DNA is the “transforming

principle” and that the DNA codes for RNA or proteins.

Distractor Rationale:

This answer suggests the student may understand that the experiment shows that DNA is

the genetic material in bacteria that corresponds to the “transforming principle,” but does

not understand that the results show no evidence that DNA codes for RNA or proteins, but

instead show that RNA and proteins are not the genetic material in cells because the

addition of enzymes that break down these components still resulted in a fully functional

compound.

(B) The results of the Avery-MacLeod-McCarty experiment show that proteins cannot be the

“transforming principle” since the proteins are easily broken down by many substances.

Distractor Rationale:

This answer suggests the student may understand that trypsin and chymotrypsin break

down proteins, but does not understand that this does not indicate that protein is the

source of the genetic material, because all of the substances in the experiment are easily

broken down by one enzyme or another. When the proteins were changed/broken down, the

compound remained functional.

(C) The results of the Avery-MacLeod-McCarty experiment show that DNA is the “transforming

principle” because enzymes that disable DNA make the “transforming” compound non-

functional.

Rationale:

This answer suggests the student understands that the experiment shows that only the

enzyme that breaks down DNA can render the transforming compound non-functional; thus,

DNA must be the heritable material that is passed from one cell to another, corresponding to

the “transforming principle.”

(D) The results of the Avery-MacLeod-McCarty experiment show that the “transforming

principle” has a double-helix structure because only the double helix can resist trypsin,

chymotrypsin, and ribonuclease.

3.4 B: DNA is the Heritable Material Quiz

8Page 2 of

PROCTOR VERSION

Distractor Rationale:

This answer suggests the student may understand that DNA is not broken down by trypsin,

chymotrypsin, or ribonuclease, but does not understand that the results do not indicate

that DNA is the genetic material, but only indicate that DNA is not affected by these

substances.

Aligned to: LO 3.4 CA 3.4: Represent Genetic Information

2. In the 1930s, most scientists agreed that proteins are the genetic material in cells. Which

statement would scientists from the 1930s most likely cite as the strongest evidence that

proteins, and not DNA, store genetic material in cells?

(A) DNA has a simple, linear structure and is found primarily in the nucleus, whereas proteins

can take on a diversity of shapes and are found throughout the cell.

Distractor Rationale:

This answer suggests the student may understand that proteins have greater structural and

functional diversity than DNA, but does not understand that this was not cited as evidence

of their ability to carry the genetic code because greater structural and functional diversity

does not necessarily make the molecules better at storing information.

(B) DNA has only two levels of organization, whereas proteins have four levels of organization,

allowing proteins to store a greater amount of information than DNA can.

Distractor Rationale:

This answer suggests the student may understand that proteins have four levels of

organization, but does not understand that this was not cited as evidence of their ability to

carry the genetic code because having more levels of organization does not necessarily

make a better “language” for a genetic code.

(C) DNA cannot initiate changes within the cell without the help of proteins, whereas proteins

can serve as enzymes and hormones, enabling proteins to interact with and cause greater

change within cells than DNA can.

Distractor Rationale:

This answer suggests the student may understand that proteins can have multiple functions,

from catalyzing reactions to serving as structural components of a cell, but does not

understand that this was not cited as evidence of the ability of proteins to carry the genetic

code because the code must store information, not perform a diversity of tasks.

3.4 B: DNA is the Heritable Material Quiz

8Page 3 of

PROCTOR VERSION

(D) DNA is made up of four different types of nucleotides, whereas proteins are made up of 20

different types of amino acids, enabling proteins to create many more chemical messengers

than DNA can.

Rationale:

This answer suggests the student understands that before DNA was identified as the

source of heritable information in the cell, scientists posited that since proteins have 20

different monomers, compared to four in DNA, proteins could make a better molecule for

storing genetic information because 20 “letters” would allow for many more “words” in the

genetic “language,” compared to only four in DNA.

Aligned to: LO 3.4 CA 3.4: Represent Genetic Information

3. In 1952, scientists Alfred Hershey and Martha Chase performed an experiment using

bacteriophages (viruses that infect bacteria) to determine the source of genetic material found in

organisms. Bacteriophages are composed of a protein shell and DNA. One group of

bacteriophages was exposed to the radioactive isotope sulfur-35 (35S) and another group of

bacteriophages was exposed to the radioactive isotope phosphorus-32 (32P). The radioactive

sulfur-35 effectively labeled the protein in the bacteriophages because only the protein, not DNA,

contains the element sulfur, and the radioactive phosphorus-32 effectively labeled the DNA in the

bacteriophages because only DNA, not the protein, contains the element phosphorus. The

bacteriophages were then allowed to infect bacterial cultures, as shown in the diagram below.

3.4 B: DNA is the Heritable Material Quiz

8Page 4 of

PROCTOR VERSION

After infection, the bacterial cultures were placed in a blender and then centrifuged to separate

the phage shells and media from the bacteria. Upon analysis of the centrifuged material, the

following observations shown in the table below were noted.

 

 

Which conclusion is best supported by the results of the Hershey-Chase experiment?

(A) Nucleic acids are the genetic material in cells, because phosphorus is a component of

nucleic acids and is transferred from the phages to the bacterial cells.

Rationale:

This answer suggests the student understands that evidence of phosphorus, not sulfur,

being transferred from a phage to bacteria supports the conclusion that nucleic acids, not

proteins, are the genetic material in organisms.

3.4 B: DNA is the Heritable Material Quiz

8Page 5 of

PROCTOR VERSION

(B) Sulfur is an important component of genetic material in phages but not in bacterial cells,

because sulfur remains in the viruses and is not observed in the bacteria.

Distractor Rationale:

This answer suggests the student may understand that sulfur is a component in viral

proteins, but does not understand that this is not evidence of its ability to carry a genetic

code because it is not the compound inserted into the bacteria by the virus.

(C) Phosphates are a key genetic material in cells, because phosphorus is transferred from the

phages to bacterial cells, and phosphorus is a component of the phosphate-sugar chains

that carry the genetic code.

Distractor Rationale:

This answer suggests the student may understand that phosphorus is found in phosphate,

and that phosphates and sugar form the “backbone” of the genetic code, but does not

understand that it is the nucleotide bases that make up the genetic code in nucleic acids.

(D) Phosphorus is the genetic material found in cells, because phosphorus is transferred from

the phage to the bacterial cells and can therefore be used to alter cell activities.

Distractor Rationale:

This answer suggests the student may understand that the experiment shows the transfer of

phosphorus from the phage to bacterial cells, but does not understand that this does not

support the conclusion that phosphorus is the sole genetic material, but instead supports the

conclusion that phosphorus is an element found in nucleic acids and provides evidence that

the nucleic acids are inserted into the bacteria by the phages.

Aligned to: LO 3.4 CA 3.4: Represent Genetic Information

3.4 B: DNA is the Heritable Material Quiz

8Page 6 of

PROCTOR VERSION

4. The table below summarizes some of the most influential experiments in the study of DNA.

In 1953, scientists Watson and Crick discovered the structure of DNA. Which statement identifies

and explains which of the experiments listed in the table was the most useful to Watson and

Crick in determining DNA’s structure?

(A) The Hershey-Chase experiment was the most useful, because the observation that

bacteriophages insert isotopes of phosphorus, but not isotopes of sulfur, into infected

bacteria cells helped Watson and Crick determine the structure of the backbone in DNA’s

double helix.

Distractor Rationale:

This answer suggests the student may understand that the Hershey-Chase experiment

showed that DNA, instead of proteins, could be the genetic material, but does not

understand that this information would not be useful in determining the structure of DNA

because it deals only with DNA’s function as a carrier of genetic information.

(B) The Avery-MacLeod-McCarty experiment was the most useful, because the discovery that

proteases and ribonucleases do not alter the molecule identified as Griffith’s “transforming

principle” showed that DNA is the source of heritable information in organisms and thus

helped Watson and Crick determine the significance of DNA’s double-helix shape.

3.4 B: DNA is the Heritable Material Quiz

8Page 7 of

PROCTOR VERSION

Distractor Rationale:

This answer suggests the student may understand that the Avery-MacLeod-McCarty

experiment shows that DNA was most likely the genetic material in organisms, but does not

understand that this evidence would not be useful in determining the structure of DNA

because it deals only with DNA’s function.

(C) Chargaff’s Rule 1 experiment was the most useful, because evidence that the percentages

of adenine and thymine are the same and the percentages of guanine and cytosine are the

same in all species helped Watson and Crick determine the structure of the DNA double

helix.

Rationale:

This answer suggests the student understands that Chargaff’s evidence of similar amounts

of AT bases, as well as GC bases, in all species would be useful data to support the

conclusion by Watson and Crick that the structure of DNA is a double strand of

complementary base pairs, because their discovery of complementary base pairing was

made possible by Chargaff’s discovery, and complementary base pairing was the key to

DNA’s structure.

(D) Chargaff’s Rule 2 experiment was the most useful, because the discovery that different

species have different relative percentages of AT and CG helped Watson and Crick

determine the structure of the DNA double helix in all species.

Distractor Rationale:

This answer suggests the student may understand that Chargaff’s discovery of variations in

the relative percentages of the four bases among species shows that DNA could be a

component of the genetic material in cells, but does not understand that the knowledge

that percentages vary from species to species would not be useful in determining the

structure of DNA.

Aligned to: LO 3.4 CA 3.4: Represent Genetic Information

3.4 B: DNA is the Heritable Material Quiz

8Page 8 of

PROCTOR VERSION