Nucleic Acids

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Slide 1

Nucleic Acids

DNA & RNA

Slide 2

What are they ?

The 4th type of macromolecules

The chemical link between generations

The source of genetic information in chromosomes

Slide 3

What do they do ?

Dictate amino-acid sequence in proteins

Give information to chromosomes, which is then passed from parent to offspring

Slide 4

What are they made of ?

Simple units called nucleotides, connected in long chains

Nucleotides have 3 parts:

1- 5-Carbon sugar (pentose)

2- Nitrogen containing base

(made of C, H and N)

3- A phosphate group ( P )

The P groups make the links that unite the sugars (hence a “sugar-phosphate backbone”

Slide 5

Two types of Nucleotides (depending on the sugar they contain)

1- Ribonucleic acids (RNA)

The pentose sugar is Ribose (has a hydroxyl group in the 3rd carbon---OH)

2- Deoxyribonucleic acids (DNA)

The pentose sugar is Deoxyribose (has just an hydrogen in the same place--- H) Deoxy = “minus oxygen”

Slide 6

DNA Nucleotides Composition (3 parts):

1- Deoxyribose sugar (no O in 3rd carbon)

2- Phosphate group

3- One of 4 types of bases (all containing nitrogen):

- Adenine

- Thymine (Only in DNA)

- Cytosine

- Guanine

Slide 7

RNA Nucleotides Composition ( 3 parts):

1- Ribose sugar (with O in 3rd carbon)

2- Phosphate group

3- One of 4 types of bases (all containing nitrogen):

- Adenine

- Uracyl (only in RNA)

- Cytosine

- Guanine

Slide 8

DNA vs RNA

DNA

1- Deoxyribose sugar

2- Bases: Adenine, Thymine, Cytosine, Guanine

3- Double-stranded helix arrangement

RNA

1- Ribose sugar

2- Bases: Adenine, Uracyl, Cytosine, Guanine

4- Single stranded

Slide 9

The Double Helix (DNA) Structural model:

Model proposed by Watson & Crick, 1953

Two sugar-phosphate strands, next to each other, but running in opposite directions.

Specific Hydrogen bonds occur among bases from one chain to the other:

A---T , C---G

Due to this specificity, a certain base on one strand indicates a certain base in the other.