Biology 2 │ Central Dogma

• DNA to DNA?

  Replication
• DNA to RNA?

  Transcription
• RNA to Protein?

  Translation
• RNA to DNA?

  Reverse Transcription
• The central dogma of molecular biology describes the flow of genetic

  information in cells from DNA to messenger RNA (mRNA) to protein. It

  states that genes specify the sequence of mRNA molecules, which in

  turn specify the sequence of proteins.
• genes were located on?

  chromosomes
• The two chemical components

  of chromosomes— DNA and protein, were therefore the leading candidates to be the genetic material.
• In 1952, American biologists Alfred Hershey and Martha Chase performed a very convincing set of experiments that showed DNA to be the genetic material of T2.
• a virus that infects the bacterium Escherichia coli (E. coli), a microbe

  normally found in the intestines of mammals?

  T2
• Viruses that exclusively infect bacteria are called bacteriophages (“bacteria-eaters”), or phages for short.
• DNA?

  Deoxyribonucleic acid
• DNA consist of repeating subunits called nucleotides
• Components of DNA

  Nitrogenous base

  A pentose sugar

  Phosphate group
• Deoxyribo refers to its form of the sugar, nucleic because DNA is located in the nuclei of eukaryotic cells, and acid because the phosphate group is in the ionized (negatively

  charged) form after donating a hydrogen atom.
• (two-carbon nitrogen rings)?

  Purines
• (Single-carbon nitrogen ring)?

  Pyrimidines
• PURINES?

  Adenine

  •Guanine
• PYRIMIDINES?

  Cytosine

  Thymine

  Uracil
• In 1953, James Watson and Francis Crick suggested a model that DNA is composed of two nucleotide chains that wrap around each other to form a double spiral –similar to a spiral staircase. This shape is

  called a double helix.
• When nucleotides are

  incorporated, adjacent

  nucleotides are linked by a

  phosphodiester bond.
• a covalent

  bond is formed between the 5’

  phosphate group of one

  nucleotide and the 3’-OH group

  of another?

  Phosphodiester bond
• The hydrogen bonds help hold the two

  chains together.
• The alternating deoxyribose sugar and

  phosphate molecules form a

  “backbone” to which the nitrogen

  containing bases face toward the

  center of the helix and that they are

  perpendicular to the sugar which is the phosphate backbone
• American biochemist Erwin Chargaff had discovered that the amount of adenine in the DNA of any one species was equal to the amount of thymine and that the

  amount of guanine was equal to that of cytosine.?

  Chargaff Rule
• A certain purine can only pair with a certain pyrimidine?

  Chargaff rule
• Cytosine bonds with guanine and adenine bonds with thymine
• C-G: form 3 hydrogen bonds

  A-T: form 2 hydrogen bonds
• This model for DNA replication is known

  as the semiconservative model

  because half of the parental molecule is maintained (conserved) in each

  daughter molecule.
• REPLICATION:

  1. initiation
  2. elongation
  3. termination
• Replication of a chromosomal

  DNA molecule begins at

  particular sites called origins of

  replication, short stretches of

  DNA having a specific sequence

  of nucleotides.
• The DNA molecule of a

  eukaryotic chromosome has

  many origins where replication

  can start simultaneously,

  thereby shortening the total

  time needed for replication.?

  Initiation
• DNA helicase disrupts the

  hydrogen bonding between

  base pairs to separate the

  strands into a Y shape, What step?

  Initiation
• Y shape known

  as the replication fork. This

  area will be the template for

  replication to begin?
• a short piece

  of RNA called a primer binds to

  the 3' end of the strand.
• . The

  primer always binds as the

  starting point for replication.
• Primers are generated by the

  enzyme DNA primase.
• The opposite orientation

  of the strands is important

  in DNA replication?

  TRUE
• DNA is directional in both

  strands, signified by a 5' and 3'

  end. This directionality is

  important for replication as it

  only progresses in the 5' to 3'

  direction.
• replication fork is bi-

  directional
• new strand (the leading

  strand) is made as a

  continuous piece.