Chapter 11 - CA 3D Assessment

Who contributed to the understanding of DNA's structure?

• Gregor Mendel

• Marie Curie

• Rosalind Franklin

• Isaac Newton

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The discovery of DNA's structure was an incremental effort over many years involving multiple scientists. Who is credited with the discovery of DNA's structure?

• Watson + Crick

• Chargaff

• Mendel

• Marie Curie

Who discovered polymerase while researching DNA replication in 1956?

• James Watson

• Francis Crick

• Arthur Kornberg

• Rosalind Franklin

1. One of the keys to understanding DNA structure is knowing how complementary bases in a DNA molecule pair up. If a single base is altered, the protein that gene encodes for might be altered, possibly affecting its function. Using Chargaff’s rule, simulate this process by filling in the correct complementary strand for this template strand in the chart below.

You may use each letter once or more than once.

b

c

d

e

C

U

A

G

T

Answer explanation

A=T

C=G

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Classify the following roles according to whether they are directly attributable to DNA or not.

Groups:

(a) DNA

,

(b) NOT DNA

• preventing mutations

• regulating body temperature

• allowing copies of genetic material to be made as part of cell division

• providing the template to build proteins.

• storing genetic information

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1. Avery built on Griffith’s work and concluded that DNA was the transformative agent that stored and transmitted genetic information between bacterial generations. But not all scientists were convinced. Hershey and Chase designed a confirming experiment using bacteriophages, which reproduce by injecting their genetic material into bacterial hosts. Hershey and Chase used unique radioactive tags: 35 S was used to tag the phage’s outer protein coat and 32 P was used to tag their DNA core. Then the phages were allowed to infect bacteria.

When the bacteria were later tested, what type of radioactivity did Hershey and Chase

find?

And what did that finding mean?

• Hershey

  and Chase found only phosphorus-32 in the bacteria. The bacteriophage was injecting its

  DNA into the host. The DNA, not proteins, was the genetic information.

• Hershey

  and Chase found only phosphorus-35 in the bacteria. The bacteriophage was injecting its

  Protein into the host. The Protein, not DNA, was the genetic information.

• Hershey

  and Chase found only phosphorus-32 in the bacteria. The bacteriophage was injecting its

  Protein into the host. The Protein, not DNA, was the genetic information.

• Hershey

  and Chase found only phosphorus-35 in the bacteria. The bacteriophage was injecting its

  Protein into the host. The Protein, not DNA, was the genetic information.

Answer explanation

Hershey and Chase labeled the protein coats of bacteriophages with sulfur-35 and their

DNA with phosphorus-32. After allowing the bacteriophages to infect bacteria, Hershey

and Chase found only phosphorus-32 in the bacteria. This meant that the whole

bacteriophage was not entering the host bacteria. The bacteriophage was injecting its

DNA into the host. The DNA, not proteins, was the genetic information.

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NGSS.HS-LS3-1

1. During meiosis and mitosis the cell must replicate its DNA, and even a small mutation caused by missing or added bases could potentially impact how the cell functions. DNA polymerase proofreads the newly made strands to ensure that there are

no errors.

Select the location(s) of the DNA polymerase as it is replicating two template strands. Mark all correct locations.

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HS-LS1-1

Before a cell divides, its DNA must be replicated without errors so that the genetic codes or proteins to be expressed properly. In​ ​ (a)   cells, which have linear chromosomes, replication occurs in ​ (b)   locations and ends when all the chromosomes are copied. In prokaryotic cells, which have ​ (c)   DNA, replication starts in only a single location and proceeds until the entire chromosome is copied.

• eukaryotic
• multiple
• circular
• prokaryotic
• linear
• singular

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1. How did the findings from Hershey and Chase’s bacteriophage experiments likely

influence the Meselson-Stahl experiment, and how might Meselson and Stahl’s results

help scientists understand how damaged DNA can be inherited by future generations?

• Hershey and Chase’s bacteriophage experiment confirmed that DNA was the genetic

  material. Meselson and Stahl could, therefore, focus their studies on replication of genetic

  material on DNA. Meselson and Stahl’s experiment showed that an error on one strand of

  DNA would be copied and transferred to next generation.

• Hershey and Chase's bacteriophage experiment disproved that DNA was the genetic

  material. Meselson and Stahl’s experiment showed that an error on one strand of

  DNA would not be copied and transferred to next generation.

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How did the results of Meselson and Stahl’s experiment confirm that DNA replication is semi-conservative?

• The single band of DNA produced in Generation 1 has an intermediate density between N-14 and N-15, indicating that the replicated DNA is a hybrid of the two forms and not an

  exact copy of either.

• The single band of DNA produced in Generation 1 has an lower density between N-14 and N-15, indicating that the replicated DNA is a copy of the two forms and not a hybrid of old and new.