DNA Structure Mastering
Regarding the structure of DNA, the covalently arranged combination of a deoxyribose and a nitrogenous base would be called a(n) ________.
nucleoside
The classic Hershey and Chase (1952) experiment that offered evidence in support of DNA being the genetic material in bacteriophages made use of which of the following labeled component(s)?
phosphorus and sulfur
What is the physical state of DNA following denaturation?
single-stranded
Reverse transcriptase is an enzyme found in association with retroviral activity. It has the property of ________.
synthesis of DNA from an RNA template
RNA differs from DNA in all of the following ways EXCEPT __________.
the 5′-3′ orientation of the polynucleotide strand.
DNA has no sulfur, and proteins have no phosphorus.
true
G and C are present in both DNA and RNA
true
Guanine and adenine are purines found in DNA
true
In RNA, uracil is present instead of the thymine in DNA.
true
In ribose, the 2' C has an OH attached to it.
true
When considering the structure of DNA, we would say that complementary strands are antiparallel
true
Given the constant diameter of 30 ÅÅ, do you think that either (i) both H and X are purines or both pyrimidines, or (ii) one is a purine and one is a pyrimidine?
They are both purines
The minor groove contains less information about the identity of base pairs than the major groove because of the
glycosidic bond angles and structure of pyrimidine bases
Considering the structure of double-stranded DNA, which kind(s) of bonds hold one complementary strand to the other?
hydrogen
What type of chemical bond holds the two strands together in double-stranded DNA?
hydrogen
Which enzyme makes DNA from an RNA template?
Reverse transcriptase
Deoxyribonuclease is an enzyme that adds 3'-hydroxyl groups to RNA
false
The transforming principle discovered by Griffith is RNA.
false
Adenine may also be named 6-amino purine.How would you name each of the other four nitrogenous bases, using this alternative system? (Note that OO is indicated by "oxy-," and CH3CH3 by "methyl.")
- 2,4-dioxy-5-methylpyrimidine - 2,4-dioxypyrimidine - 2-oxy-4-aminopyrimidine - 2-amino-6-oxypurine
Which of the following are true about the two strands of the double helix?
- 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
hydrogen bonds
- electrostatic charge attraction - weak bonds (easy to break) - responsible for base complementary
covalent bonds
- sharing of electrons between two or more atoms - strong bonds (difficult to break)
Why did Hershey and Chase use the isotopes 32P and 35S in their experiments?
32P labeled DNA only; 35S labeled protein only
If 15% of the nitrogenous bases in a sample of DNA from a particular organism is thymine, what percentage should be cytosine?
35%
Write the complementary sequence for the following DNA sequence, in order from 3' to 5': 5′−CGATATTGAGCTAAGCTT−3′
3′− GCTATAACTCGATTCGAA −5'
What is the complementary DNA sequence to 5′ ATGCTTGACTG 3′?
5′ CAGTCAAGCAT 3′
In an analysis of the nucleotide composition of double-stranded DNA to see which bases are equivalent in concentration, which of the following would be true?
A + C = G + T
What is the hyperchromic effect?
A hyperchromic effect is the increased absorption of UV light as double-stranded DNA is converted to single-stranded DNA.
To help achieve proper base pairing and hence form a double helix, which condition must be met?
A purine base must pair with a pyrimidine base
If a DNA-binding protein "reads" a short stretch of DNA and detects the following "second" genetic code provided by the functional groups located on each base as H-HD-CH3-HA-HA-HA-HA-HD, then what is the corresponding sequence of bases?
C-T-G-A
What results did Avery, McLeod, and McCarty obtain in their experiments with virulent bacteria?
DNase destroyed the transforming activity.
Which technique can be used to identify the location of genes on a chromosome?
FISH
Which statement is true?
G-C base pairs have three hydrogen bonds while A-T base pairs have two hydrogen bonds
What molecules are removed from the structures when the linkages between the components are formed?
H2O
Which of the following statements about linkage of bases to the sugar are true?
In purines, the N-9 atom is covalently bonded to the C-1' of the sugar. In pyrimidines, the N-1 atom is covalently bonded to the C-1' of the sugar.
Which of the following is NOT a characteristic of the genetic material?
It is composed of protein.
Newsdate: March 1, 2030. A unique creature has been discovered during exploration of outer space. Recently, its genetic material has been isolated and analyzed. This material is similar in some ways to DNA in its chemical makeup. It contains in abundance the 4-carbon sugar erythrose and a molar equivalent of phosphate groups. In addition, it contains six nitrogenous bases: adenine (A), guanine (G), thymine (T), cytosine (C), hypoxanthine (H), and xanthine (X). These bases exist in the following relative proportions:A = T = H and C = G = XX-ray diffraction studies have established a regularity in the molecule and a constant diameter of about 30 ÅÅ. Together, these data have suggested a model for the structure of this molecule. Propose a general model of this molecule. Describe it briefly.
It is probable that the unique creature's DNA follows the same structural plan as "earth-type" DNA It is a triple helix.
What are the two major components of the Tobacco Mosaic Virus?
RNA and protein
List three main differences between DNA and RNA.
RNA often occurs as both single- and partially double-stranded forms, whereas DNA most often occurs in a double- stranded form. Uracil in RNA replaces thymine in DNA. Ribose in RNA replaces deoxyribose in DNA.
Which statement about the polarity of DNA strands is true?
The 3' end has a free OH group
What does Tm imply?
The Tm is the temperature at which half of the sample is denatured.
In the classic experiment conducted by Hershey and Chase, why was the pellet radioactive in the centrifuge tube that contained bacteria with viruses?
The bacteria were in the pellet, and many contained the radioactive viral DNA
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. There are two hydrogen bonds forming the A to T pair and three forming the G to C pair. Bases are stacked 0.34 nmnm apart.
Hershey and Chase used labeled DNA and protein to determine that DNA is the genetic material in bacteria.
false
Which statement is true?
The more hydrogen bonds between bases, the higher the temperature needed to separate the pair.
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
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
Which of the following is true about the overall structure of the DNA helix?
There is one complete turn for each 3.4 nmnm, which constitutes 10 bases per turn The double helix is right-handed. The double helix is approximately 20 Angstroms in diameter.
What base-pairing properties must exist for H and for X in the model?
X C, and G are hydrogen bonded to one another H, A, and T are hydrogen bonded to one another
If you were to try and pair a thymine with a cytosine (a non Watson-Crick base pairing), then would you expect to see any stability with respect to the hydrogen bonding (assuming the geometrical configurations of both bases were favorable to each other)? If yes, then how many hydrogen bonds could form between these two bases?
Yes, two hydrogen bonds could form between thymine and cytosine.
What is the chemical basis of molecular hybridization?
base complementarity
The basic structure of a nucleotide includes ________.
base, sugar, and phosphate
Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in prokaryotes and eukaryotes?
double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0
Avery et al. (1944) determined that DNA is the genetic material in T2 bacteriophage.
false
