Post on 02-Jan-2016
Structure of DNADiscovered in 1950s by Rosalind
Franklin using X-ray diffraction.
“Double Helix” term coined by Watson and Crick in the 1950s as well.
DNA Structure
A molecule of DNA is made up of millions of tiny subunits called Nucleotides.
Each nucleotide consists of:1. Phosphate group2. Pentose sugar3. Nitrogenous base
NucleotidesThe phosphate and sugar form the
backbone of the DNA molecule, whereas the bases form the “rungs”.
There are four types of nitrogenous bases.
Nucleotides (Practice)
A
Adenine(Purine)
T
Thymine(Pyrimidines)
G
Guanine(Purine)
C
Cytosine(Pyrimidines)
NucleotidesEach base will only bond with one
other specific base.
Adenine (A)Thymine (T)
Cytosine (C)Guanine (G)
Form a base pair.
Form a base pair.
DNA StructureBecause of this complementary base
pairing,
the order of the bases in one strand determines
the order of the bases in the other strand.
BASE PAIRING IS ALWAYS EQUAL!!!!(Ex: 25% A=25% T)
DNA StructureA gene is a section of DNA that codes
for a protein.
Each unique gene has a unique sequence of bases.
This unique sequence of bases will code for the production of a unique protein.
It is these proteins and combination of proteins that give us a unique phenotype.
DNA is copied during a process called replication!
What phase of the cell cycle does DNA replication occur?
Replication results=one new strand & one original strand