General Biology I - BSC 1010C - Chapter 16: The Molecular
Basis of Inheritance Questions With Complete Solutions
Describe Griffith's experiment. How did the results support that
a molecule was responsible for transmitting genetic
information? Correct Answers Frederick Griffith studied two
strains of the bacterium Streptococcus pneumoniae: the S
(smooth) strain and the R (rough) strain. The living S cells were
deadly to the mice, while the living R cells were non-deadly.
When Griffith killed S cells with heat and injected them into the
mice, the mice remained healthy. When he combined heat-killed
S cells and living R cells, the mice died. In the mouse's blood
sample, living S cells were found; they could reproduce,
yielding more S cells. Griffith concluded that horizontal gene
transfer was occurring from dead S-cells to living R-cells. His
experiment showed that some molecules represented genetic
information, which was moving from one bacteria to another.
Describe Hershey and Chase's experiment. How did the results
support the idea that DNA is the molecule that represents the
genetic information? Correct Answers In 1952, Hershey and
Chase performed an experiment showing that DNA is the
genetic material of a phage known as T2, one of many phages
that infect E. coli. They used radioactive sulfur and phosphorus
to trace the fates of protein and DNA, respectively, of T2 phages
that infected bacterial cells. When proteins were labeled,
radioactivity remained outside the cells, but when DNA was
labeled, radioactivity was found inside the cells. Phage DNA
entered bacterial cells, but phage proteins did not. Hershey and
Chase concluded that DNA, not protein, functions as the genetic
material.
, Describe the experiment of Meselson and Stahl and how the
results of the experiment supported the semiconservative model
of replication. Correct Answers Meselson and Stahl cultured E.
coli for several generations in a medium containing nucleotide
precursors labeled with a heavy isotope of nitrogen, 15N. They
then transferred the bacteria to a medium with 14N, a lighter
isotope. They extracted DNA from the bacteria in the two
samples and then centrifuged each DNA sample to separate
DNA of different densities. The results showed that the first
replication in the 14N medium produced a brand of hybrid
DNA, which eliminated the conservative model. The second
replication produced both light and hybrid DNA, which
supported the semiconservative model. Both scientists then
concluded that DNA replicated is semiconservative.
Diagram of DNA replication Correct Answers
Direction of replication Correct Answers 5' to 3' direction; In
DNA synthesis, DNA strands always elongate in a 5' to 3'
direction.
DNA polymerase I Correct Answers An enzyme that removes
RNA nucleotides of the adjacent primer and replaces them with
DNA nucleotides, one at a time.
DNA polymerase III Correct Answers An enzyme that adds
DNA nucleotides to the RNA primer and then continues adding
DNA nucleotides, complementary to the parental DNA template
strand, to the growing end of the new DNA strand. It can add
Basis of Inheritance Questions With Complete Solutions
Describe Griffith's experiment. How did the results support that
a molecule was responsible for transmitting genetic
information? Correct Answers Frederick Griffith studied two
strains of the bacterium Streptococcus pneumoniae: the S
(smooth) strain and the R (rough) strain. The living S cells were
deadly to the mice, while the living R cells were non-deadly.
When Griffith killed S cells with heat and injected them into the
mice, the mice remained healthy. When he combined heat-killed
S cells and living R cells, the mice died. In the mouse's blood
sample, living S cells were found; they could reproduce,
yielding more S cells. Griffith concluded that horizontal gene
transfer was occurring from dead S-cells to living R-cells. His
experiment showed that some molecules represented genetic
information, which was moving from one bacteria to another.
Describe Hershey and Chase's experiment. How did the results
support the idea that DNA is the molecule that represents the
genetic information? Correct Answers In 1952, Hershey and
Chase performed an experiment showing that DNA is the
genetic material of a phage known as T2, one of many phages
that infect E. coli. They used radioactive sulfur and phosphorus
to trace the fates of protein and DNA, respectively, of T2 phages
that infected bacterial cells. When proteins were labeled,
radioactivity remained outside the cells, but when DNA was
labeled, radioactivity was found inside the cells. Phage DNA
entered bacterial cells, but phage proteins did not. Hershey and
Chase concluded that DNA, not protein, functions as the genetic
material.
, Describe the experiment of Meselson and Stahl and how the
results of the experiment supported the semiconservative model
of replication. Correct Answers Meselson and Stahl cultured E.
coli for several generations in a medium containing nucleotide
precursors labeled with a heavy isotope of nitrogen, 15N. They
then transferred the bacteria to a medium with 14N, a lighter
isotope. They extracted DNA from the bacteria in the two
samples and then centrifuged each DNA sample to separate
DNA of different densities. The results showed that the first
replication in the 14N medium produced a brand of hybrid
DNA, which eliminated the conservative model. The second
replication produced both light and hybrid DNA, which
supported the semiconservative model. Both scientists then
concluded that DNA replicated is semiconservative.
Diagram of DNA replication Correct Answers
Direction of replication Correct Answers 5' to 3' direction; In
DNA synthesis, DNA strands always elongate in a 5' to 3'
direction.
DNA polymerase I Correct Answers An enzyme that removes
RNA nucleotides of the adjacent primer and replaces them with
DNA nucleotides, one at a time.
DNA polymerase III Correct Answers An enzyme that adds
DNA nucleotides to the RNA primer and then continues adding
DNA nucleotides, complementary to the parental DNA template
strand, to the growing end of the new DNA strand. It can add
