3. PHOSPHATE
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Derived from phosphoric acid (H3PO4)
Phosphate residue is attached to pentose
sugar DNA/RNA via the 5’C by a
phosphodiester link
Acidic, Nucleic acid
All residues in the DNA/RNA carry a
negative charge in physiologic Ph
NUCLEOSIDE FORMATION
NUCLEIC ACID
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NUCLEOSIDE – a two sub unit molecule in
which a pentose sugar is bonded to a
nitrogen containing a heterocyclic base.
RULE:
• Base is always attached to Carbon 1 of the
sugar
• Condensation reaction – A molecule of
water is formed as the 2 molecules bond
RIBONUCLEIC ACID (RNA)
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together.
NUCLEOSIDE FORMATION
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Pyrimidine bases, suffix – idine is used
(cytidine, thymidine, uridine)
Purine bases, the suffix – osine is used
(adenosine, guanosine)
Prefix deoxy – indicates that sugar unit is
deoxyribose (no oxygen)
DEOXYRIBOSE – DNA
RIBOSE - RNA
NUCLEOTIDE FORMATION
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Phosphate group is attached to the sugar
at carbon 5 position via phosphoester
linkage
Water molecule is produced formation
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Nucleotide polymer in which each of the
monomers contains ribose, a phosphate
group, and one of the heterocyclic bases:
Adenine, Cytosine, Guanine or Uracil
Occurs in all parts of cell
Primary function is Synthesis of Proteins
DEOXYRIBONUCLEIC ACID (DNA)
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Nucleotide polymer in which each of the
monomer
contains
deoxyribose,
a
phosphate group, and one of the
heterocyclic bases: Adenine, Cytosine,
Guanine, or Thymine
Found within the cell nucleus
Primary function is the storage and transfer
of genetic information
This information is used to control many
functions of a living cell
DNA is passed from existing cells to new
cells during cell division
SABIDURIA, NICOLE ANN A
2
PRIMARY STRUCTURE OF NUCLEIC ACID
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Polynucleotide chains have sense or
directionality (3’ unreacted hydroxyl group
and unreacted 5’ phosphate group)
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– Nature of two
polynucleotide chains in DNA double helix
means that there is a 5’ end and a 3’ end at
both ends of double helix.
COMPLEMENTARY BASES – Pairs of
bases in a nucleic acid structure that can
hydrogen bond to each other.
A-T, G-C
ANTIPARALLEL
Polynucleotide
have
individuality
(nucleotide base sequence) Basis for the
different amino acids.
BASE PAIRING
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The size of the interior of the DNA
double helix, limits the base pairs that
can hydrogen bond to one another.
Only pairs involving one small base
(pyrimidine) and one large base
(purine) correctly fit.
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PREDICT THE SEQUENCE OF BASES
IN
THE
DNA
STRAND
COMPLEMENTARY TO THE SINGLE
DNA STRAND SHOWN:
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ANS: 3’ T-T-A-C-G-T-C-G-A 5’
DNA:
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A-T (Adenine-Thymine) (apples in the
tree)
G-C (Cytosine-Guanine) (car in the
garage)
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5’ G-T-A-A-C-T-C-G-A 3’
ANS: 3’ C-A-T-T-G-A-G-C-T 5’
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The sugar unit in the backbone of RNA is
ribose
In RNA, Uracil instead of thymine, pairs
with adenine
RNA is a single stranded molecule.
RNA molecules are smaller than DNA
molecules
RNA:
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RIBONUCLEIC ACIDS
A-U (Adenine-Uracil)
G-C (Guanine- Cytosine)
WATSON-CRICK MODEL
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5’ A-A-T-G-C-A-G-C-T 3’
Combination of two single strands
The double Helix
Sugar-phosphate backbone outside, bases
inside
Bases form specific base pairs, held
together by hydrogen bonds
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TYPES OF RNA MOLECULES
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Heterogenous nuclear RNA (hnRNA)
Messenger RNA (mRNA)
Small nuclear RNA (snRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
HETEROGENOUS NUCLEAR RNA (hnRNA)
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RNA formed by DNA transcription
Post-transcription processing converts the
hnRNA to mRNA
SABIDURIA, NICOLE ANN A
2
MESSENGER RNA (Mrna)
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RNA that carries instructions for protein
synthesis (genetic information) to the sites
for protein synthesis
SMALL NUCLEAR RNA (snRNA)
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RNA that facilitates the conversion of
heterogenous nuclear RNA to messenger
RNA
RIBOSOMAL RNA (rRNA)
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RNA that combines with specific proteins to
form ribosomes, the physical sites for
protein synthesis.
TRANSFER RNA (tRNA)
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RNA that delivers amino acids to the sites
for protein synthesis
Smallest RNA
SABIDURIA, NICOLE ANN A
2