Question 1

When Frederick Griffith injected dead bacteria of the virulent S strain into mice,the mice:

Accepted Answer

When Frederick Griffith injected dead bacteria of the virulent S strain into mice, the mice remained healthy because the bacteria were dead and could not cause infection.

Question 2

The significance of the Griffith,Avery and Hershey-Chase experiments was that they demonstrated that:

Accepted Answer

The Griffith, Avery, and Hershey-Chase experiments provided evidence that DNA, not protein, was the molecule of heredity. These experiments showed that DNA could carry genetic information and could be replicated during cell division. This discovery revolutionized the field of genetics and led to a better understanding of how traits are passed from one generation to the next.

Question 3

The building blocks of DNA are called:

Accepted Answer

The building blocks of DNA are called nucleotides. Each nucleotide is made up of a sugar molecule, a phosphate group, and one of four nitrogenous bases: adenine (A), cytosine (C), guanine (G), or thymine (T). These building blocks link together to form the double helix structure of DNA.

Question 4

Based on which of the following pieces of evidence about the transforming agent did Avery conclude that DNA is the hereditary material?

Accepted Answer

Avery's experiments concluded that DNA is the hereditary material based on several lines of evidence: the purified material had the same elements as DNA, it behaved like DNA in an ultracentrifuge, it was not destroyed by protein-digesting enzymes, and it was destroyed by DNA-digesting enzymes.

Question 5

Which scientists determined that DNA synthesis is semiconservative?

Accepted Answer

Matthew Meselson and Franklin Stahl performed an experiment in 1958 that demonstrated that DNA replication is semiconservative, meaning that each daughter DNA molecule is composed of one original parental strand and one newly synthesized strand. Their experiment used heavy nitrogen isotopes to label parental DNA and lighter nitrogen isotopes to label newly synthesized DNA. After several rounds of replication, they were able to observe two distinct bands of DNA in a density gradient, one with a density corresponding to fully labeled DNA and the other with a density corresponding to partially labeled DNA. This supported the idea that DNA replication involves the separation of parental strands and the synthesis of new complementary strands.

Question 6

A plant species has its DNA analyzed.The results show that 28% of its nitrogen bases are guanine.What is the percent represented by thymine?

Accepted Answer

The answer of A plant species has its DNA analyzed.The...

Question 7

If one strand of a DNA molecule has the base sequence ATTGCAT,its complementary strand will have the sequence:

Accepted Answer

The complementary strand of DNA has base pairing rules of A-T and C-G. Therefore, the complementary strand to ATTGCAT would be TAACGTA as each base pairs with its complementary base (A with T and T with A, C with G and G with C).

Question 8

When Griffith injected a mixture of dead S bacteria and live,capsuleless R bacteria,the mice:

Accepted Answer

When Griffith injected the mixture of dead S bacteria and live, capsuleless R bacteria into the mice, he observed that the mice died of blood poisoning. This happened because the genetic material from the dead S bacteria was taken up by the live R bacteria, transforming them into virulent S bacteria that could cause disease.

Question 9

When Frederick Griffith infected mice with a virulent strain of Streptococcus pneumoniae,the mice:

Accepted Answer

When Frederick Griffith infected mice with a virulent strain of Streptococcus pneumoniae, the mice died of blood poisoning. This is because the virulent strain is capable of causing disease and can be fatal in mice.

Question 10

How many carbon atoms does deoxyribose have?

Accepted Answer

Deoxyribose, a sugar component of DNA, has 5 carbon atoms.

Question 11

Biochemist Erwin Chargaff found that in DNA there was a special relationship between individual bases that we now refer to as Chargaff's rule.His observation was that:

Accepted Answer

Chargaff's rule states that in DNA, the base pairs are always A paired with T and G paired with C, which is best represented by choice A.

Question 12

All of the following are correct about DNA replication except:

Accepted Answer

Helicase is the enzyme responsible for unwinding the double-stranded DNA during replication. It does not rewind the DNA after replication is finished.

Question 13

The enzyme that joins the ends of newly synthesized segments of DNA after the primers have been removed is:

Accepted Answer

DNA ligase is the enzyme responsible for joining the ends of newly synthesized segments of DNA after the primers have been removed. This process is known as "ligation" and it is essential for the completion of DNA replication and repair.

Question 14

Hershey and Chase tagged the DNA of viruses with radioactive phosphorus,and their protein coats with radioactive sulfur.When the viruses were allowed to infect bacteria,what did the viruses transfer to the bacteria?

Accepted Answer

Hershey and Chase tagged the DNA of the virus with radioactive phosphorus, so when the virus infected the bacteria, it transferred the radioactive phosphorus to the bacteria. They did not tag the protein coats with radioactive phosphorus. Therefore, neither radioactive sulfur nor the protein coats were transferred to the bacteria.

Question 15

When Frederick Griffith infected mice with S.pneumoniae that lacked a capsule,the mice:

Accepted Answer

When Frederick Griffith infected mice with S. pneumoniae that lacked a capsule, the mice remained healthy. This experiment was important in demonstrating that the capsule of S. pneumoniae is necessary for virulence, as without the capsule, the bacteria were unable to cause disease.

Question 16

In the Griffith experiment,why did the mice become ill when injected with a mixture of dead S bacteria and live,capsuleless R bacteria?

Accepted Answer

The mice became ill when injected with a mixture of dead S bacteria and live, capsuleless R bacteria because DNA was passed from the dead virulent S bacteria to the live nonvirulent R bacteria, which transformed them into virulent bacteria capable of causing disease. This phenomenon was named transformation by Griffith.

Question 17

Which choice describes how the DNA molecule replicates?

Accepted Answer

DNA replication is semiconservative, which means that during replication, each strand of the original DNA molecule serves as a template for the synthesis of a new complementary strand, resulting in two new DNA molecules, each containing one original strand and one new complementary strand. This has been experimentally proven and widely accepted as the mechanism of DNA replication.

Question 18

Which scientists are credited for deducing the true structure of DNA?

Accepted Answer

James Watson and Francis Crick are credited for deducing the true structure of DNA in 1953. Rosalind Franklin's X-ray crystallography work provided crucial data that helped Watson and Crick develop their model. Martha Chase and Frederick Griffith made important contributions to the understanding of DNA but did not deduce its true structure. Rachel Carson was an environmental scientist and writer known for her work on pesticide regulation, and Oswald Avery was a biologist known for his work on DNA as the transforming principle.

Question 19

Which scientist's work first suggested that DNA had the shape of a helix?

Accepted Answer

Rosalind Franklin's X-ray crystallography images of DNA fibers provided evidence that DNA had a helical shape.

Question 20

Meselson and Stahl proved that:

Accepted Answer

Meselson and Stahl's experiment proved that DNA replicates in a semi-conservative manner, meaning that each new double helix contains one old and one new strand of DNA. This was demonstrated through the use of heavy isotopes of nitrogen to track the replication process. The experiment did not prove that DNA is the genetic material, that DNA is made from nucleotides, or that DNA contains nitrogen, as these were already established scientific facts.

Quiz 11: DNA: The Genetic Material