DNA v.s. RNA Structure [The Central Dogma of Biology]

• DNA

  Nucleotides are the basic building block of nucleic acids (RNA and DNA).

  ○ They are made up of Pentose Sugar (Deoxyribose in DNA; Ribose in RNA), a

  Phosphate group, and a Nitrogenous base.

  ○ The backbone of DNA are the phosphate group and the sugar
• DNA

  DNA stands for Deoxyribonucleic Acid

  ○ Deoxyribonucleic meaning that the pentose sugar present in DNA is lacking

  an oxygen atom.
• DNA

  Hereditary information is encoded in the DNA

  ○ This encoded DNA is then reproduced to all cells of the body.
• DNA

  It directs the development of the following traits:

  ○ Biochemical

  ○ Anatomical

  ○ Physiological

  ○ Behavioral traits (to some extent)
• DNA

  Nitrogenous bases are Cytosine, Guanine, Adenine, Thymine (Uracil for RNA).

  ○ The two main classification of nitrogenous bases are Purines (Adenine and Guanine) and Pyrimidines (Cytosine, Thymine, and Uracil).
• DNA as a Genetic Material Carrier

  It was discovered that there were two main chemical components of DNA. DNA and Protein, which emerged as the leading candidates for the carriers of genetic material.

  ○ In the 1940s, the case for proteins as the genetic material carrier was stronger due to having more knowledge in comparison to that of nucleic acid where little was known about it.
• DNA as a Genetic Material Carrier

  • Frederick Griffith
  • Hershey and Chase
  • Erwin Chargaff
• DNA as a Genetic Material Carrier

  Frederick Griffith

  • He is a British Medical Officer who was trying to develop a vaccine for pneumonia
  • He studied Streptococcus pneumoniae, a pneumonia causing bacteria.
  • In Griffith’s experiment, the smooth strain was killed then mixed it with the rough strain.
  • ○ Despite already killing the smooth strain, the rough strain still became pathogenic.
  • ○ He concluded that some chemical component of the dead pathogenic cells caused this heritable change and called this phenomenon transformation
• DNA as a Genetic Material Carrier

  Frederick Griffith

  S-strain

  • Also known as the “smooth strain”
  • It has a capsule outside of its cell wall
  • It is pathogenic (disease-causing)

  R-strain

  • Also known as the “rough strain”
  • It does not have a capsule outside of its cell wall
  • it is non-pathogenic
• DNA as a Genetic Material Carrier

  Hershey and Chase

  • Hershey and Chase’s experiment using bacteriophages (“bacteria-eaters”)
  • ○ When it was time for the bacteriophage to infect the bacteria, it was found that only the DNA of the bacteriophage was transferred causing the infection of the bacteria and not the protein.
  • They concluded that DNA was indeed functioning as the genetic information carrier and not the protein.
• DNA as a Genetic Material Carrier

  Erwin Chargaff

  • In 1950, Chargaff reported that the base composition of DNA varies from one species to another.
  • ○ This evidence of molecular diversity among species made DNA a more credible candidate for the genetic material.
  • Chargaff also noticed a peculiar regularity in the ratios of nucleotide bases.
  • ○ The number of adenines (A) was almost always equal to the number of thymines (T) while the number of guanines (G) was almost always equal to the number of cytosines (C).
• DNA as a Genetic Material Carrier

  Chargaff's Rule

  • These two findings became the basis of the Chargaff’s rule wherein:
  • ○ DNA base composition varies between species
  • ○ The percentages of A and T bases are roughly equal, as are those of G and C bases
• DNA structure

  Maurice Wilkins and Rosalind Franklin

  • Wilkins and Franklin were using a technique called x-ray crystallography to study molecular structure
  • At this time, Rosalind produced an x-ray diffraction image of the DNA molecule unit
  • In Franklin’s work, she had concluded that DNA was composed of two antiparallel sugar phosphate backbones found at the exterior structure of the DNA while the nitrogenous bases were at the interior of the structure
  • ○ First strand: 5’(5 prime) to 3’(3 prime)
  • ○ Second strand: 3’(3 prime) to 5’(5 prime)
• DNA Structure

  James Watson and Francis Crick

  • They deduced that DNA was a double helix.
  • ○ This deduction was based on the image produced by Franklin.
  • Watson and Crick reasoned that there must be additional specificity of base pairing dictated by the structure of the nitrogenous bases.
  • ○ This was due to the measurements presented at the image of the DNA.
  • ○ If both are purines then the gap is too wide
  • ○ If both are pyrimidines then the gap is too narrow
  • ○ If one is a purine and the other is a pyrimidine then the width is consistent with the x-ray data
• DNA

  double stranded
• DNA

  always double helix
• DNA

  Pentose sugar is called Deoxyribose (since it lacks an extra oxygen)
• DNA

  Adenine is paired with Thymine, Guanine is paired with Cytosine
• DNA

  Primary function is to carry genetic information
• RNA

  single stranded
• RNA

  can vary in shape
• RNA

  Pentose sugar is called Ribose (since it has an extra oxygen)
• RNA

  Adenine is paired with Uracil (since Thymine is no longer present in RNA)

  Guanine is paired with Cytosine
• RNA

  Primary function is to aid in the process of protein synthesis as seen in the 3

  types of RNA:

  • Messenger RNA(mRNA)

  • Ribosomal RNA (rRNA)

  • Transfer RNA (tRNA)
• C

  DNA is responsible for directing the development of the following traits except:

  a.Biochemical

  b. Anatomical

  c. Physical

  d. Physiological
• 57

  
  

  If a DNA molecule has 150 base pairs and 12% of it is thymine. How many guanine are there based on Chargaff’s rule?
• Transformation

  
  

  What is the phenomenon where a strain of bacteria is changed by a chemical component of another strain of bacteria?
• b

  
  

  What is the primary function of the RNA?

  a.To carry genetic information

  b. To aid in the process of protein synthesis

  c. To direct or instruct protein synthesis

  d. To protect the DNA
• Rosalind Franklin

  
  

  Who was responsible for producing an x-ray diffraction image of the DNA molecule Unit?
• Erwin Chargaff

  
  

  Who discovered that adenine is equal to thymine and guanine is equal to cytosine?
• DNA and protein

  What were the two first leading candidates for the carriers of genetic material?
• Hershey and Chase

  Who were the ones responsible for concluding that DNA was the one functioning as the genetic material carrier through their bacteriophage experiment?
• 54%

  If the AT content of a DNA molecule is 46%, what are the percentages of the GC content?
• Thymine

  What nitrogenous base does Uracil replace among the DNA nitrogenous bases?
• X-ray crystallography

  What is the technique used by Wilkins and Franklin in studying molecular structure?
• b

  Which among the following is not a main component of a nucleotide?

  a.Pentose sugar

  b. Hydrogen Ions

  c. Phosphate Group

  d. Nitrogenous Base
• Frederick Griffith

  Who studied Streptococcus pneumoniae, a pneumonia causing bacteria, and discovered the phenomenon transformation?
• exterior, interior

  In Franklin’s work, antiparallel sugar phosphate backbones were found in the ____ while nitrogenous bases were found in the ____ of the DNA structure?
• James Watson and Francis Crick

  Who deduced that DNA is a double helix?