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DNA
DNA
STRUCTURE
THE MOLECULE OF HEREDITY
DNA = Deoxyribose Nucleic Acid
photo 51
The structure of DNA is referred to as a DOUBLE HELIX
Two complimentary strands of
nucleotides held together
Hydrogen Bonds
DNA made up of repeating “building blocks”
called NUCLEOTIDES.
Three parts of a DNA Nucleotide:
1. Deoxyribose Sugar
2. Phosphate Group
3. Nitrogen Base
There are four different Nitrogenous Bases)
1. Adenine (A)
2. Guanine (G)
3. Cytosine (C)
4. Thymine (T)
The “Twisted Ladder” Analogy
Sides of the ladder =“BACKBONE” and consist of alternating
phosphate groups and sugars held together by covalent bonds
The “RUNGS” = nitrogen bases
BASE PAIRING
Adenine forms H- bonds with Thymine (A-T)
Guanine forms H-bonds with Cytosine (G-C)
DNA and all its glory!!!
STRUCTURE OF RNA
RNA = Ribonucleic Acid
3 MAJOR DIFFERENCES:
(1) single-stranded instead of
double-stranded
(2) ribose sugar instead of
dexoyribose
(3) uracil N-base instead of
thymine
3 TYPES OF RNA
mRNA
1. mRNA (messenger) - carries
DNA’s information out of the
nucleus
AA
2. tRNA (transfer) - carries amino
acids to growing protein chain
3. rRNA (ribosomal) – combines
with protein to make-up
ribosome
tRNA
rRNA
+
protein
ribosome