DNA Composition and Structure

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Questions and Answers

Which sugar is found in RNA?

  • Deoxyribose
  • Fructose
  • Glucose
  • Ribose (correct)

Which nitrogenous base is a purine?

  • Adenine (correct)
  • Uracil
  • Thymine
  • Cytosine

Which component is found in a nucleotide but not in a nucleoside?

  • Sugar
  • Hydrogen bond
  • Phosphate (correct)
  • Nitrogenous base

What type of bond links the sugars and phosphates in a nucleic acid?

<p>Phosphodiester bond (C)</p> Signup and view all the answers

According to Chargaff's rules, which pair bases are equal in amount?

<p>Adenine and thymine (C)</p> Signup and view all the answers

Which nitrogenous base is found in RNA but not in DNA?

<p>Uracil (C)</p> Signup and view all the answers

What does it mean for DNA replication to be semi-conservative?

<p>Each new DNA molecule contains one original strand and one new strand. (C)</p> Signup and view all the answers

What did the Hershey-Chase experiment conclude about genetic material?

<p>DNA is the genetic material of the bacteriophage (C)</p> Signup and view all the answers

Which base pairs with thymine (T) during DNA replication?

<p>Adenine (A) (C)</p> Signup and view all the answers

What kind of bonds connect adenine (A) to thymine (T) in a DNA molecule?

<p>Two hydrogen bonds (B)</p> Signup and view all the answers

What is the main requirement for the semi-conservative mechanism of DNA replication?

<p>Complementary base pairing (C)</p> Signup and view all the answers

Which form of DNA is most commonly found in solutions?

<p>B-DNA (A)</p> Signup and view all the answers

Which process is illustrated by the creation of new DNA strands from existing ones?

<p>DNA Replication (A)</p> Signup and view all the answers

How many hydrogen bonds connect cytosine (C) to guanine (G) in a DNA molecule?

<p>Three (B)</p> Signup and view all the answers

Which base pairs with guanine (G) during DNA replication?

<p>Cytosine (C) (A)</p> Signup and view all the answers

Which of the following is not a component of DNA?

<p>Phenylalanine (A)</p> Signup and view all the answers

Which of the following statements is true about the new DNA strands formed during replication?

<p>They consist of one original and one new strand. (B)</p> Signup and view all the answers

What did the Meselson-Stahl experiment demonstrate about DNA replication?

<p>DNA replication is semi-conservative (A)</p> Signup and view all the answers

Which form of DNA is characterized by a long, slender, left-handed helix?

<p>Z-DNA (C)</p> Signup and view all the answers

Why are major and minor grooves formed in the DNA helix?

<p>Because the two sugar-phosphate backbones are not exactly aligned (A)</p> Signup and view all the answers

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Study Notes

DNA Composition

  • Deoxyribose is the sugar found in DNA, while Ribose is found in RNA.

Nitrogenous Bases

  • Adenine, Guanine, Cytosine, and Thymine are the nitrogenous bases found in DNA.
  • Uracil is found in RNA, replacing Thymine.
  • Purines are nitrogen bases containing two rings, including Adenine and Guanine.
  • Pyrimidines are nitrogen bases containing one ring, including Cytosine, Thymine, and Uracil.

Phosphate

  • The phosphate group is represented by O-P-O- OH.

Nucleosides vs. Nucleotides

  • A Nucleoside or Deoxynucleoside is a nitrogenous base bound to a sugar.
  • A Nucleotide or Deoxynucleotide is a nitrogenous base bound to a sugar and a phosphate group.
  • A Nucleic Acid is a polymer (chain) of nucleotides.

Facts

  • Nucleic acids are polymers, and their monomers are called nucleotides.
  • Nucleotides consist of a base, sugar, and phosphate group.
  • Sugar can be deoxyribose or ribose.
  • Phosphate groups link sugar molecules together through phosphodiester bonds.

Famous Experiments

Chargaff's Rules

  • The amounts of Adenine (A) and Thymine (T) are equal, and the amounts of Guanine (G) and Cytosine (C) are equal.
  • The amounts of A&T and G&C differ between species.

The Hershey-Chase Experiment

  • The experiment showed that DNA, not protein, carries genetic information.
  • Radioactive phosphorus, which labels DNA, was found in bacteria, while radioactive sulfur, which labels protein, was not.

DNA Composition - Double Helix

  • The double helix structure of DNA consists of anti-parallel strands.
  • Adenine (A) pairs with Thymine (T) through two hydrogen bonds.
  • Cytosine (C) pairs with Guanine (G) through three hydrogen bonds.
  • The major and minor grooves are formed due to the alignment of sugar-phosphate backbones.

DNA Conformations

  • A-DNA is a short, wide, right-handed helix.
  • B-DNA is the most common DNA form in solution, a right-handed helix.
  • Z-DNA is a long, slender, left-handed helix.

The Meselson-Stahl Experiment

  • The experiment showed that DNA replication is semi-conservative, not conservative or dispersive.
  • Each new strand contains one original and one new strand.

DNA Replication

  • DNA replication is semi-conservative and depends on complementary base pairing.
  • Each new strand contains one original and one new strand, making it a semi-conservative process.

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