The History & The History & Structure of the DNA Structure of the DNA

MoleculeMolecule

CHAPTER 10 CHAPTER 10

PART 1PART 1

The History of the DNA The History of the DNA Molecule Molecule

The Impossibility of InformationThe Impossibility of Information

The DNA molecule is one of the The DNA molecule is one of the greatest scientific discoveries of all greatest scientific discoveries of all time. First described by James Watson time. First described by James Watson and Francis Crick in 1953, DNA is the and Francis Crick in 1953, DNA is the famous storehouse of genetics that famous storehouse of genetics that establishes each organism's physical establishes each organism's physical characteristics.characteristics.

DNA HistoryDNA History

GriffithGriffith – Experimented on mice and – Experimented on mice and observed some harmless strains of observed some harmless strains of bacteria could change into harmful strains. bacteria could change into harmful strains. He called this transformation. He called this transformation.

AveryAvery – Discovered that DNA is the – Discovered that DNA is the nucleic acid that stores and transmits the nucleic acid that stores and transmits the genetic information from one generation to genetic information from one generation to the next.the next.

More DNA HistoryMore DNA History

Hershey-Chase – Hershey-Chase – Concluded that the Concluded that the genetic material in genetic material in bacteria was DNA not bacteria was DNA not proteinsproteins

http://highered.mcgraw-hill.com/olc/dl/120076/http://highered.mcgraw-hill.com/olc/dl/120076/bio21.swfbio21.swf

Watson & Crick – Watson & Crick – created the double created the double helix model for DNA.helix model for DNA.

NucleotidesNucleotides

1.1. DNA is made up of subunits DNA is made up of subunits

which scientists called which scientists called

nucleotides. nucleotides.

A nucleotide is a chemical compound that consists of 3 portions: a nitrogenous base, a sugar, and one or more phosphate groups.

DNA's structure.DNA's structure.1.1. There are 4 different bases in a DNA There are 4 different bases in a DNA

molecule: molecule:

a.a. adenine (a purine )adenine (a purine )b.b. cytosine (a pyrimidine ) cytosine (a pyrimidine ) c.c. guanine (a purine) guanine (a purine) d.d. thymine (a pyrimidine)thymine (a pyrimidine)

PURINES - nitrogenous bases that have a double ring of carbon and nitrogen atoms PYRIMIDINES - nitrogenous bases that have a single ring of carbon and nitrogen atoms

Base Pairing RulesBase Pairing Rules

Chargaff’s RulesChargaff’s Rules

In DNA, Cytosine on In DNA, Cytosine on one strand always one strand always pairs with Guanine on pairs with Guanine on the opposite strand.the opposite strand.

Adenine always pairs Adenine always pairs with thyminewith thymine

DNA DNA ReplicationReplication

How DNA Replication OccursHow DNA Replication Occurs

DNA replication is the process by which DNA replication is the process by which DNA is copied in a cell before a cell DNA is copied in a cell before a cell divides by mitosis, meiosis, or binary divides by mitosis, meiosis, or binary fission.fission.

How It OccursHow It OccursDNA replication is carried out by a series DNA replication is carried out by a series of enzymes.of enzymes.The enzymes unzip the DNA molecule The enzymes unzip the DNA molecule creating two strands that serve as creating two strands that serve as templates. (helicase enzyme moves along templates. (helicase enzyme moves along DNA molecule breaking the hydrogen DNA molecule breaking the hydrogen bonds)bonds)The Y- shaped region the results when the The Y- shaped region the results when the two strands separate is called a replication two strands separate is called a replication forkfork

Complimentary bases are added to the Complimentary bases are added to the strands by enzymes called DNA strands by enzymes called DNA Polymerase that are found floating freely Polymerase that are found floating freely inside the nucleus, for example a strand of inside the nucleus, for example a strand of DNA with the bases ATTCGAG would DNA with the bases ATTCGAG would have a complimentary strand of have a complimentary strand of TAAGCTCTAAGCTC

Each new DNA molecule has one new Each new DNA molecule has one new stand and one strand from the original stand and one strand from the original molecule. (this is called semi-conservative molecule. (this is called semi-conservative replication)replication)

The enzyme DNA polymerase, the principal The enzyme DNA polymerase, the principal enzyme, “proofreads” the new DNA enzyme, “proofreads” the new DNA strands, helping to maximize the odds that strands, helping to maximize the odds that each molecule is a perfect copy of the each molecule is a perfect copy of the original.original.

DNA polymerase Finish replicating theDNA polymerase Finish replicating the

DNA and fall offDNA and fall offhttp://www.youtube.com/watch?v=zdDkiRw1PdU&feature=relatedhttp://www.youtube.com/watch?v=zdDkiRw1PdU&feature=related

DNA REPLICATIONDNA REPLICATION

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