Ch. 9

The Hershey and Chase experiments involved the preparation of two different types of radioactively labeled phage. Which of the following best explains why two preparations were required? -Establishing the identity of the genetic material required observation of two phage generations. -It was necessary that each of the two phage components, DNA and protein, be identifiable upon recovery at the end of the experiment. -The bacteriophage used in the experiments was a T2 phage. -Each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. Which of the following statements best represents the central conclusion of the Hershey-Chase experiments? -Some viruses can infect bacteria. -DNA is the identity of the hereditary material in phage T2. -When radioactive sulfur is supplied in a growth medium, it is primarily DNA that incorporates radioactive label. -Phage T2 is capable of replicating within a bacterial host. Which of the following outcomes would be most likely if the Hershey-Chase experiments were repeated without the step involving the blender? -The phage would fail to infect bacteria. -Both preparations of infected bacteria would exhibit radioactivity. -Neither preparation of infected bacteria would exhibit radioactivity. -Both preparations of infected bacteria would contain both P32 and S35.

- It was necessary that each of the two phage components, DNA and protein, be identifiable upon recovery at the end of the experiment. - DNA is the identity of the hereditary material in phage T2. - Both preparations of infected bacteria would exhibit radioactivity.

In 1928, Frederick Griffith established that _______. -heat-killed bacteria harbor the constituent(s) necessary to convey genetic properties to living bacteria -mouse DNA could be transferred into bacterial cells -mice could be infected with bacteria -proteases have no effect on DNA To be certain that the extract prepared from virulent cells still contained the transforming principle that was present prior to lysis, Avery _______. -incubated virulent cells with the complete extract -destroyed proteins, polysaccharides, DNA, and RNA contained in the extract -injected mice with the extract -incubated nonvirulent cells with the complete extract If Avery had observed transformation using only the extracts containing degraded DNA, degraded RNA, and degraded protein, but NOT the extract containing degraded polysaccharides, he would have concluded that _______. -mice with diets rich in polysaccharides are resistant to bacterial infection -RNA is the genetic material -the preparations were contaminated -polysaccharides are the genetic material

- heat-killed bacteria harbor the constituent(s) necessary to convey genetic properties to living bacteria - incubated nonvirulent cells with the complete extract -polysaccharides are the genetic material

Which of the following are true about nitrogenous bases and base pairing? -The base composition is such that A equals T and G equals C. -The base composition is such that T equals C and A equals G. -There are three hydrogen bonds forming the A to T pair and two forming the G to C pair. -There are two hydrogen bonds forming the A to T pair and three forming the G to C pair. -Bases are stacked 0.34 nm apart. -Bases are stacked 0.50 nm apart. Which of the following are true about the two strands of the double helix? -Phosphodiester bonds hold the two polynucleotide chains together. -Hydrogen bonds hold the two polynucleotide strands together. -The hydrophobic phosphodiester backbone is located in the center of the molecule, whereas the hydrophilic nitrogenous bases are on the outside. -The hydrophobic nitrogenous bases are located in the center of the molecule, whereas the hydrophilic phosphodiester backbone is on the outside. -The two strands are antiparallel. -The two strands are parallel. Which of the following is true about the overall structure of the DNA helix? -There is one complete turn for each 34 nm, which constitutes 46 bases per turn. -There is one complete turn for each 3.4 nm, which constitutes 10 bases per turn. -The double helix is right-handed. -The double helix is left-handed. -The double helix is approximately 20 Angstroms in diameter. -The double helix is approximately 34 Angstroms in diameter.

-The base composition is such that A equals T and G equals C. -There are two hydrogen bonds forming the A to T pair and three forming the G to C pair. -Bases are stacked 0.34 nm apart. -hydrogen bonds hold the two polynucleotide strands together. -The hydrophobic nitrogenous bases are located in the center of the molecule, whereas the hydrophilic phosphodiester backbone is on the outside. -The two strands are antiparallel. -There is one complete turn for each 3.4 nm, which constitutes 10 bases per turn. -The double helix is right-handed. -The double helix is approximately 20 Angstroms in diameter.

List three main differences between DNA and RNA. -Ribose in RNA replaces thymine in DNA. -Uracil in RNA replaces thymine in DNA. -Ribose in RNA replaces deoxyribose in DNA. -RNA often occurs as both single- and partially double-stranded forms, whereas DNA most often occurs in a double- stranded form. -DNA often occurs as both single- and partially double-stranded forms, whereas RNA most often occurs in a double- stranded form. -Uracil in RNA replaces deoxyribose in DNA.

-Uracil in RNA replaces thymine in DNA. -Ribose in RNA replaces deoxyribose in DNA. -RNA often occurs as both single- and partially double-stranded forms, whereas DNA most often occurs in a double- stranded form.

ribosomal RNA messenger RNA transfer RNA

-catalyzes the formation of peptide bonds between amino acids & is a structural part of the enzyme responsible for translation -sequence specifies the order of amino acids in a protein & carries information from the nucleus to cytoplasm -has a cloverleaf secondary structure & acts as the link between codons and amino acids

Exclusively DNA Both DNA & RNA Exclusively RNA Identify three possible components of a DNA nucleotide. -adenine, phosphate group, ribose -guanine, phosphate group, ribose -deoxyribose, phosphate group, uracil -cytidine, phosphate group, ribose -deoxyribose, phosphate group, thymine -cytosine, phosphate group, ribose

-thymine & deoxyribose -adenine, guanine, cytosine, & phosphate -uracil & ribose -deoxyribose, phosphate group, thymine

Why did Hershey and Chase use the isotopes 32P and 35S in their experiments? -35S labeled lipids only; 32P labeled DNA only -35S labeled DNA only; 32P labeled protein only -32P labeled DNA only; 35S labeled carbohydrates only -32P labeled DNA only; 35S labeled protein only

32P labeled DNA only; 35S labeled protein only

Write the complementary sequence for the following DNA sequence, in order from 3' to 5': -5′−CGATATTGAGCTAAGCTT−3′

3′− GCTATAACTCGATTCGAA −5′

The genetic material must be stable enough to maintain information in _____________ from one cell to the next and one organism to the next.

storage

RNA differs from DNA in all EXCEPT which of the following ways? -the presence of uracil -the 5'-3' orientation of the polynucleotide strand -the sugar molecule -the number of different functions performed

the 5'-3' orientation of the polynucleotide strand

replication

the process that leads to the production of identical copies of the existing genetic information.

expression

the processing of genetic information that results in synthesis of proteins which contribute to the phenotype of the organism.

mutation

the random variation of genetic material that provides the basis for evolution.

Some viruses replicate by first producing a DNA copy of their RNA genome. -True -False

true

When Avery and his colleagues had obtained the transforming factor from the IIIS virulent cells, they treated the fraction with proteases, ribonuclease, and deoxyribonuclease, followed by the assay for retention or loss of transforming ability. What was the purpose of these experiments? -to determine the enzyme that can suppress virulence -to determine the exact molecular species of the "transforming principle" -to prove the stability of the "transforming priniciple" in a typical cell medium -to prove that transforming ability does not depend on presence of any enzymes What was the result? What conclusions were drawn? -The DNA was proven to be the "transforming principle". Treatment with deoxyribonuclease resulted in the loss of transforming ability. -The RNA was proven to be the "transforming principle". Treatment with ribonuclease resulted in the loss of transforming ability. -The deoxyribonuclease was proven to be the "transforming principle". Treatment with deoxyribonuclease resulted in the retention of transforming ability. -Protein was proven to be the "transforming principle". Treatment with protease resulted in the loss of transforming ability.

-to determine the exact molecular species of the "transforming principle" -the DNA was proven to be the "transforming principle". Treatment with deoxyribonuclease resulted in the loss of transforming ability.

Guanine and adenine are purines found in DNA. -True -False Which of the following statements about DNA structure is true? -The nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions. -Nucleic acids are formed through phosphodiester bonds that link nucleosides together. -Hydrogen bonds formed between the sugar‑phosphate backbones of the two DNA chains help to stabilize DNA structure. -The pentose sugar in DNA is ribose. What is the complementary DNA sequence to 5′ ATGCTTGACTG 3′? -5′ CAGTCAAGCAT 3′ -5′ ACTCTACGTAG 3′ -5′ ATGCTTGACTG 3′ -5′ TACGAACTGAC 3′

-true -the nucleic acid strands in a DNA molecule are oriented antiparallel to each other, meaning they run in opposite directions. -5′ CAGTCAAGCAT 3′

All EXCEPT which of the following statements are evidence that DNA, and not protein, is the genetic material in eukaryotes as well as bacteria? -DNA is located only where the primary genetic function is known to occur. -Introduction of a cloned DNA into another organism results in the production of the corresponding protein product. -UV light is most mutagenic at a wavelength at which DNA and RNA strongly absorb. -DNA has four nucleotides.

DNA has four nucleotides.

What results did Avery, McLeod, and McCarty obtain in their experiments with virulent bacteria? -Protease destroyed the transforming activity. -RNase destroyed the transforming activity. -DNase destroyed the transforming activity. -The transforming principle was too complex and difficult to be purified.

DNase destroyed the transforming activity.

All EXCEPT which of the following are characteristics of the genetic material? -It must be capable of change. -It must be replicated accurately. -It contains all the information needed for growth, development, and reproduction of the organism. -It is composed of protein.

It is composed of protein.

Watson and Crick used information from several individuals to construct their model of DNA. Whose X-ray diffraction studies were critical to their work? -Linus Pauling -Erwin Chargaff -Rosalind Franklin -Phoebus Levene

Rosalind Franklin

What observation did Griffith make in his experiments with Streptococcus pneumoniae? -The mouse did not survive when injected with a mixture of live, avirulent (rough) Streptococcus pneumoniae and heat-killed, virulent Streptococcus pneumoniae. -The heat-killed, virulent Streptococcus pneumoniae was lethal to the mouse. -The mouse survived injection of live virulent (smooth) Streptococcus pneumoniae. -DNA is the genetic material.

The mouse did not survive when injected with a mixture of live, avirulent (rough) Streptococcus pneumoniae and heat-killed, virulent Streptococcus pneumoniae.