DNA Structure

DNAStructur

e

DNA StructureDNA consists of two molecules that are

arranged into a ladder-like structure called a Double Helix.

A molecule of DNA is made up of millions of tiny subunits called Nucleotides.

Each nucleotide consists of:1. Phosphate group2. Pentose sugar3. Nitrogenous base

Nucleotides

Phosphate

Pentose

Sugar

Nitrogenous

Base

NucleotidesThe phosphate and sugar form the

backbone of the DNA molecule, whereas the bases form the “rungs”.

There are four types of nitrogenous bases.

Nucleotides

A

AdenineT

Thymine

G

GuanineC

Cytosine

NucleotidesEach base will only

bond with one other specific base.

Adenine (A)Thymine (T)

Cytosine (C)Guanine (G)

Form a base pair.

Form a base pair.

DNA Structure

DNA StructureBecause of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

G

G

A

T

T

A

A

C

T

G

C

A

T

C

DNA StructureTo crack the genetic code found in

DNA we need to look at the sequence of bases.

The bases are arranged in triplets called codons.

A G G - C T C - A A G - T C C - T A GT C C - G A G - T T C - A G G - A T C

DNA StructureA gene is a section of DNA that codes for a

protein.

Each unique gene has a unique sequence of bases.

This unique sequence of bases will code for the production of a unique protein.

It is these proteins and combination of proteins that give us a unique phenotype.

DNA ReplicationDNA replication is the process of

copying a double-stranded DNA molecule.

Produces two copies of DNA that each contain one of the parent strands and one entirely new strand.

DNA Replication

DNA Replication1. An enzyme called Helicase “unzips”

the base pairs by breaking the bonds.

G

G

A

T

T

A

A

C

T

G

C

A

T

C

Helicase

DNA Replication1. An enzyme called Helicase “unzips”

the base pairs by breaking the bonds.

2. Raw materials are needed to “re-build” the two parent strands.

G

G

A

T

T

AA

C

T

G

C

A

T

C

DNA Replication1. An enzyme called Helicase “unzips”

the base pairs by breaking the bonds.

2. Raw materials are needed to “re-build” the two parent strands.

3. Another enzyme called DNA Polymerase is used to arrange nucleotides in a new complimentary strand.

G

G

G

G

A

T

T

AA

C

T

G

C

A

T

C

A

T

T

A

C

DNAPolymerase

DNA ReplicationThe result is two

identical copies of DNA, each with an original parent strand and a new strand.

A

C

T

G

C

A

T

G

G

A

T

T

A

C

G

G

A

T

T

A

A

C

T

G

C

A

T

C

G

G

A

T

T

A

A

C

T

G

C

A

T

C