Nucleic acids like DNA and RNA are macromolecules that contain genetic information and dictate the amino acid sequences of proteins. They are composed of nucleotides, which each contain a sugar, phosphate group, and nitrogenous base. DNA contains the sugars deoxyribose and bases adenine, thymine, cytosine, and guanine. It exists as a double-stranded helix. RNA contains the sugar ribose and bases adenine, uracil, cytosine, and guanine. It is usually single-stranded. DNA stores genetic information in genes as triplet codons that are translated into amino acids to make proteins.

1. Nucleic AcidsNucleic Acids
DNA & RNADNA & RNA

2. What are they ?What are they ?
The 4The 4thth
type oftype of
macromoleculesmacromolecules
The chemical link betweenThe chemical link between
generationsgenerations
The source ofThe source of geneticgenetic
information in chromosomesinformation in chromosomes

3. What do they do ?What do they do ?
DictateDictate amino-acidamino-acid
sequence in proteinssequence in proteins
Give information toGive information to
chromosomes, which is thenchromosomes, which is then
passed from parent topassed from parent to
offspringoffspring

4. What are they made of ?What are they made of ?
 Simple units calledSimple units called nucleotidesnucleotides,,
connected in long chainsconnected in long chains
 NucleotidesNucleotides have 3 parts:have 3 parts:
1- 5-Carbon sugar (pentose)1- 5-Carbon sugar (pentose)
2- Nitrogen containing base2- Nitrogen containing base
(made of C, H and N)(made of C, H and N)
3- A phosphate group ( P )3- A phosphate group ( P )
 The P groups make the links thatThe P groups make the links that
unite the sugars (hence a “unite the sugars (hence a “sugar-sugar-
phosphate backbone”phosphate backbone”

5. Two types of NucleotidesTwo types of Nucleotides
(depending on the sugar they(depending on the sugar they
contain)contain)
1-1- Ribonucleic acids (RNA)Ribonucleic acids (RNA)
The pentose sugar isThe pentose sugar is RiboseRibose
(has a hydroxyl group in the 3(has a hydroxyl group in the 3rdrd
carbon---carbon---OHOH))
2-2- Deoxyribonucleic acids (DNA)Deoxyribonucleic acids (DNA)
The pentose sugar isThe pentose sugar is
DeoxyriboseDeoxyribose (has just an(has just an
hydrogenhydrogen in the same place---in the same place---
H)H) DDeoxy = “minus oxygen”eoxy = “minus oxygen”

6. DNADNA NucleotidesNucleotides
Composition (3 parts):Composition (3 parts):
1-1- DDeoxyribose sugar (eoxyribose sugar (no Ono O in 3in 3rdrd
carbon)carbon)
2- Phosphate group2- Phosphate group
3-3- One of 4 types of basesOne of 4 types of bases (all(all
containing nitrogen):containing nitrogen):
- Adenine- Adenine
-- Thymine (Only in DNA)Thymine (Only in DNA)
- Cytosine- Cytosine
- Guanine- Guanine

7. RNARNA NucleotidesNucleotides
Composition ( 3 parts):Composition ( 3 parts):
1-1- RRibose sugar (ibose sugar (with Owith O in 3in 3rdrd
carbon)carbon)
2- Phosphate group2- Phosphate group
3-3- One of 4 types of basesOne of 4 types of bases (all(all
containing nitrogen):containing nitrogen):
- Adenine- Adenine
-- Uracyl (only in RNA)Uracyl (only in RNA)
- Cytosine- Cytosine
- Guanine- Guanine

8. DNADNA vsvs RNARNA
 DNADNA
1-1- DDeoxyribose sugareoxyribose sugar
2- Bases: Adenine,2- Bases: Adenine, ThymineThymine, Cytosine,, Cytosine,
GuanineGuanine
3-3- DoubleDouble-stranded helix arrangement-stranded helix arrangement
 RNARNA
1-1- RRibose sugaribose sugar
2- Bases: Adenine,2- Bases: Adenine, UracylUracyl, Cytosine,, Cytosine,
GuanineGuanine
4-4- SingleSingle strandedstranded

9. The Double Helix (DNA)The Double Helix (DNA)
Structural model:Structural model:
 Model proposed by Watson & Crick, 1953Model proposed by Watson & Crick, 1953
 Two sugar-phosphate strands, next to eachTwo sugar-phosphate strands, next to each
other, but running in opposite directions.other, but running in opposite directions.
 Specific Hydrogen bondsSpecific Hydrogen bonds occur among basesoccur among bases
from one chain to the other:from one chain to the other:
A---TA---T ,, C---GC---G
Due to this specificity, a certain base onDue to this specificity, a certain base on
one strand indicates a certain base in theone strand indicates a certain base in the
otherother..
 The 2 strands intertwine, forming aThe 2 strands intertwine, forming a
double-helix that winds around a centraldouble-helix that winds around a central
axisaxis

10. How DNA WorksHow DNA Works
1-1- DNA stores genetic information inDNA stores genetic information in
segments calledsegments called genesgenes
2- The DNA code is in2- The DNA code is in TriTriplet Codonsplet Codons
(short sequences of(short sequences of 33 nucleotidesnucleotides
each)each)
3- Certain3- Certain codonscodons are translated byare translated by
the cell intothe cell into certain Aminocertain Amino
acids.acids.
4. Thus, the4. Thus, the sequence of nucleotidessequence of nucleotides inin
DNA indicate aDNA indicate a sequence of Aminosequence of Amino
acidsacids in ain a proteinprotein..