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DNA Structure
DNA stands for...
Deoxyribonucleic Acid
Chromosomes and DNA
•DNA, genes, and
chromosomes compose
the molecular basis for
heredity.
•A chromosome is a
structure in the nucleus of
a cell consisting of one
long thread of DNA that is
tightly coiled
Genes and DNA
• A gene is a specific location
on a chromosome,
consisting of a segment of
DNA
• Each chromosome consists
of hundreds of genes
determining the many
proteins for an organism.
Discovering the structure of DNA
• Discovered in 1953 by James Watson & Francis Crick
- double helix; twisted ladder; spiral staircase
DNA Structure cont.
Rosalind Franklin XRay Defraction Image of DNA
proved that it was a double helix/twisted
ladder shape
Discovery of DNA Timeline
DNA:
codes for your genes (traits)
•made of repeating subunits called nucleotides
What is a nucleotide?
Three components:
1. PHOSPHATE
2. DEOXYRIBOSE (sugar)
3. BASE (A,T,G,C)
Base-Pair Rule
Adenine <==> Thymine
Guanine <==> Cytosine
The sides/backbone of the DNA
ladder are phosphate
& sugar held together
by hydrogen bonds.
Base Pair Rule
One side: A T A T C A
Other side:
T G C
G G G