2: DNA Structure

DNA composition, base pairing, and double-helix structure.

True/False Statements About DNA Structure (BIOL 351)

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Which one of the following statements is TRUE regarding the structure of DNA?

• A. the DNA bases for each strand face the outside of the helix
• B. covalent bonds hold the two strands together
• C. purine bases pair up with like purine bases
• D. the helix is made of amino acids
• E. DNA contains two strands, with each strand running in opposite directions

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True/False Statements About DNA Structure

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Which one of the following statements is TRUE of the structure of DNA?

• A. the DNA double helix has a consistent diameter
• B. the helix is made of amino acids
• C. covalent bonds hold the two strands together
• D. the DNA strands are uniformly positively charged
• E. purine bases pair up with like purine bases

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True/False Statements About DNA Melting Temperature (Tm)

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Which one of the following statements is TRUE concerning melting temperature (T_m) of DNA?

• A. The melting temperature (T_m) of a DNA strand goes up (increases)
  when the adenine (A) + thymine (T) base pairing content increases.
• B. The melting temperature (T_m) of a DNA strand goes up (increases)
  when the amount of nucleobases with amino groups adenine (A) + cytosine (C), decreases.
• C. The melting temperature (T_m) of a DNA strand is the temperature
  at which half of strands are single-stranded and the other half are double-stranded.
• D. The melting temperature (T_m) of a DNA strand goes up (increases)
  when the amount of purine nucleobases, adenine (A) + guanine (G), decreases.
• E. The melting temperature (T_m) of a DNA strand goes up (increases)
  when the amount of nucleobases with ketone groups, guanine (G) + thymine (T), decreases.

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True/False Statements About Factors That Increase DNA Melting Temperature (Tm)

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Which one of the following will INCREASE the melting temperature (T_m) of a DNA strand?

• A. decrease the amount of purine nucleobases, adenine (A) + guanine (G)
• B. decrease the amount of adenine (A) (A) + thymine (T) (T) base pairing
• C. decrease the amount of cytosine (C) + guanine (G) base pairing
• D. decrease the amount of nucleobases with ketone groups, guanine (G) + thymine (T)
• E. decrease the amount of pyrimidine nucleobases, cytosine (C) + thymine (T)

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True/False Statements About Factors That Decrease DNA Melting Temperature (Tm)

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Which one of the following will DECREASE the melting temperature (T_m) of a DNA strand?

• A. increase the amount of nucleobases with ketone groups, guanine (G) + thymine (T)
• B. increase the amount of cytosine (C) + guanine (G) base pairing
• C. increase the amount of pyrimidine nucleobases, cytosine (C) + thymine (T)
• D. increase the amount of adenine (A) (A) + thymine (T) (T) base pairing
• E. increase the amount of nucleobases with amino groups adenine (A) + cytosine (C)

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True/False Statements About Nucleotide Components

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Which one of the following is NOT one of the three (3) major components of a DNA or RNA nucleotide?

• A. phosphate group
• B. nucleobase
• C. deoxyribose
• D. cytosol

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True/False Statements About RNA and DNA Differences (BIOL 301)

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Which one of the following statements is TRUE concerning differences between RNA and DNA?

• A. RNA is made of nucleotides, DNA is made of amino acids
• B. RNA is unable to form a double-stranded helix
• C. RNA nucleotides are missing the 2′ hydroxide (-OH) group compared to DNA
• D. the DNA sugar is ribose, RNA has a different sugar
• E. RNA is usually single-stranded (simplex), whereas DNA is usually double-stranded (duplex)

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True/False Statements About RNA and DNA Differences

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Which one of the following statements is FALSE concerning differences between RNA and DNA?

• A. double-stranded DNA is mostly in the B-form helix, whereas double-stranded RNA is mostly in the A-form helix
• B. Both DNA and RNA have a negative charge
• C. the DNA sugar is ribose, RNA has a different sugar
• D. Both double-stranded DNA and double-stranded RNA have major and minor grooves
• E. DNA is usually double-stranded (duplex), whereas RNA is usually single-stranded (simplex)

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DNA Base Composition Using Chargaff's Rules (5 Choices)

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According to Chargaff's rules concerning the base pairing composition in double-stranded DNA, consider a sample where the percentage composition of 13% is cytosine.
What are the percentages of the other three bases?

• A. adenine (A): 37% — guanine (G): 13% — thymine (T): 37%
• B. adenine (A): 37% — guanine (G): 37% — thymine (T): 13%
• C. adenine (A): 25% — guanine (G): 25% — thymine (T): 37%
• D. adenine (A): 25% — guanine (G): 37% — thymine (T): 25%
• E. adenine (A): 13% — guanine (G): 37% — thymine (T): 37%

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Complementary DNA Sequences Without Direction Labels

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DNA is organized as a double helix where two strands run in opposite, or anti-parallel, directions. The ends of these strands are referred to as 5′ (five prime) and 3′ (three prime) ends. The strands are held together by hydrogen bonds between complementary base pairs. Specifically, adenine (A) forms a pair with thymine (T), and guanine (G) pairs with cytosine (C). This base pairing is critical for the stability of the DNA molecule and is central to processes like DNA replication and transcription.

 

T

A

G

,

C

A

G

,

G

T

C

Which one of the following DNA sequences is complementary to the direction-less DNA sequence shown above?

• A.  

  A

  T

  C

  ,

  G

  T

  C

  ,

  C

  A

  G

• B.  

  G

  C

  T

  ,

  A

  T

  C

  ,

  C

  A

  G

• C.  

  T

  A

  G

  ,

  C

  T

  C

  ,

  C

  A

  G

• D.  

  C

  T

  G

  ,

  G

  A

  C

  ,

  G

  A

  T

• E.  

  A

  T

  C

  ,

  G

  C

  T

  ,

  G

  G

  A

Check Answer

 

DNA Melting Temperature Extremes from Sequence (12 Bases)

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Which one of the following DNA sequences below will have the HIGHEST melting point (T_m).

Hint: I tried to make this question pretty easy and it does not require a calculator.

• A.

  5′–

  G

  T

  T

  ,

  A

  T

  T

  ,

  A

  C

  A

  ,

  G

  T

  A

  –3′

  3′–

  C

  A

  A

  ,

  T

  A

  A

  ,

  T

  G

  T

  ,

  C

  A

  T

  –5′

• B.

  5′–

  G

  C

  G

  ,

  G

  T

  A

  ,

  G

  A

  G

  ,

  G

  A

  G

  –3′

  3′–

  C

  G

  C

  ,

  C

  A

  T

  ,

  C

  T

  C

  ,

  C

  T

  C

  –5′

• C.

  5′–

  G

  G

  T

  ,

  A

  T

  T

  ,

  A

  T

  T

  ,

  A

  T

  A

  –3′

  3′–

  C

  C

  A

  ,

  T

  A

  A

  ,

  T

  A

  A

  ,

  T

  A

  T

  –5′

• D.

  5′–

  G

  C

  C

  ,

  G

  A

  T

  ,

  T

  A

  T

  ,

  A

  T

  T

  –3′

  3′–

  C

  G

  G

  ,

  C

  T

  A

  ,

  A

  T

  A

  ,

  T

  A

  A

  –5′

Check Answer