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Nucleic Acids
Big Idea 3: Living systems store,
retrieve, transmit, and respond to
info essential to life processes.
Essential Knowledge
• 3A1: DNA, and in some cases RNA, is the
primary source of heritable information.
Nucleic Acids
• Store and transmit hereditary information
• Amino acid sequence of a polypeptide is
programmed by a unit of inheritance called a gene
• Genes are found on chromosomes.
Nucleic Acids
•Large, complex molecules composed of C, O, H, N,
and P.
•2 types are RNA, ribonucleic acid and DNA,
deoxyribonucleic acid.
DNA
RNA
Prokaryotes
• Earliest cells
• Smaller than Eukaryotes!
• No nucleus (home for DNA)
Prokaryotic DNA
• Is housed in a region called the nucleoid
Prok. DNA
• Is usually
small and
circular
• Has plasmids:
small, extrachromosomal,
double
stranded, and
circular DNA
Viruses and Eukaryotes can have plasmids
too…
Herstory
• Rosalind Franklin: British
scientist (working in Maurice
Wilkins lab) who took an X ray
diffraction image of DNA,
1952
• Led to double helix shape
discovery by Watson and Crick
Photo 51
HIStory
• Watson and Crick
used Franklin’s image
to create the double
helix DNA model in
1953.
• Won Nobel Prize in
1962,w/ Wilkins.
Double Helix Structure
Nucleic Acid Structure
• Made of nucleotides; both RNA and
DNA.
Each nucleotide
contains:
• 1 Phosphate
Group
• 1 Sugar
• 1 Nitrogen
Base
Phosphate
• PO4
• Makes up a
part of the
DNA/RNA
backbone
Sugar
• In DNA, sugar is
deoxyribose
• In RNA, sugar is
ribose
• Binds to
Nitrogen Base
• Is in backbone
of DNA/RNA
Fig. 5-27c-2
Sugars
Deoxyribose (in DNA)
(c) Nucleoside components: sugars
Ribose (in RNA)
DNA Nitrogen Bases
•
•
•
•
Adenine
Thymine
Guanine
Cytosine
Conserved Through Evolution!
DNA Base Pairing Rules (Chargaff’s Rules)
• A only binds with T
• C only binds with G
• H bonds hold Nitrogen bases together
RNA Nitrogen Bases
•
•
•
•
•
Adenine
Cytosine
Guanine
Uracil
NO
Thymine!
Fig. 5-27c-1
Nitrogenous bases
Pyrimidines
Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)
Pyrimidines: Single Ring Structure: CTU
Purines
Adenine (A)
Guanine (G)
(c) Nucleoside
components:
bases
Purines:
Doublenitrogenous
Ring Structure,
GA
DNA: Double Stranded,
RNA Single Stranded
DNA is
AntiParallel
Fig. 5-27ab
5' end
5'C
3’ carbon and 5’ carbon bind to
PO4 phosphodiester linkage
3'C
Nucleoside
Nitrogenous
base
5'C
Phosphate
group
5'C
3'C
(b) Nucleotide
3' end
(a) Polynucleotide, or nucleic acid
3'C
Sugar
(pentose)
DNA Replication
• DNA provides directions for its own
replication  ensure continuous
inheritance of DNA
DNA Replication
• Before a cell
divides  must
duplicate its DNA.
• Each strand of DNA
will serve as a
template/model for
a new strand of
DNA
(semiconservative).
st
DNA Replication 1 Step
DNA
Helicase
• Enzyme called DNA helicase unzips
and unwinds a portion of DNA.
• Enzyme helps breaks apart H connect
N bases. (A,T,C,G)
DNA Replication: 2nd Step
• 2nd enzyme called
DNA polymerase III
comes along and
begins to add
complementary base
pairs to nitrogen
bases.
• Works in 5’ to 3’
fashion…
• Video Clip!
DNA Replication
Other Enzymes
Involved:
Ligase: Glues back
sugar-phosphate
backbone
Topoisomerase:
Regulates
overwinding/
underwinding of
DNA by cutting
backbone
http://highered.mcgrawhill.com/sites/9834092339/stu
dent_view0/chapter14/dna_re
plication.html
Practice!
• If one side of DNA reads
CTCT, what would the
complement side of DNA
read? Write down on paper!
GAGA!
Then, The Cell Divides…
• Mitosis: Makes 2 identical diploid (2
copies of chromosomes) cells from 1
parent cell: IPMAT