Transcript 7.1 DNA Structure

8.1 DNA Structure & Function
Nucleic Acids
• DNA & RNA are nucleic acids
• Monomer?
▫ Nucleotides
P
N- Base
5-C
Sugar
DNA History
• Watson & Crick developed
“double-helix” model of DNA
structure in 1953
• Used work of Rosalind
Franklin
http://www.nature.com/scitable/topicpage/rosalin
d-franklin-a-crucial-contribution-6538012
DNA Structure
• Double helix
▫ Two chains (strands) of nucleotides twisted
around each other
• Within each strand:
▫ Sugar-Phosphate Backbone formed by sugar
& phosphates of nucleotides
▫ Nucleotides of the backbone are connected by
phosphate bonds
DNA Structure
Phosphate bond
http://click4biology.info/c4b/3/images/3.3/dinucleotide.gif
Making DNA
DNA Structure
• How are the two strands of nucleotides
connected?
• Two strands arrange themselves so that the Nbases are in the center
• N-bases complementary bond with each other
using hydrogen bonds
▫ Cytosine – Guanine (C-G)
▫ Adenine – Thymine (A-T)
DNA Function
• DNA acts as a blueprint for all life
• DNA is arranged in genes
▫ Gene: sequence of nucleotides in DNA
▫ Each chromosome contains hundreds of genes!
• One gene gives instructions for making one
specific protein
▫ Remember: protein function
 Enzymes, transport, movement, immunity, etc
DNA Function
• Each protein is responsible for a trait
▫ Trait: physical manifestation of gene
• Each human has the same genes, but we are not
all the same. Why?
▫ Different order of nucleotides in our genes!
RNA Structure
• Single-helix
▫ Only one strand of nucleotides
• The 5-C sugar in RNA is ribose
• Does not have the base thymine, but has the
base uracil instead
http://www.tildee.com/Xbwj6f
RNA Function
• Enzymes make a RNA copy of one DNA gene
▫ RNA is much smaller than DNA
• The cell uses this RNA copy to make a protein
Central Dogma
DNA
RNA
Protein