DNADNA is often called the blueprint of life..

DeoxyriboNucleic Acid DNA contains the instructions for making proteins within the cell.

DNA is a very long polymer.

The basic shape is like a twisted ladder or zipper.

This is called a double helix.

Two strands twisted together.

The backbone of the molecule is alternating phosphatephosphate and deoxyribose parts.

The teeth are nitrogenous basesbases..

phosphate

deoxyribose

bases

One deoxyribose together with its phosphate and

base make a nucleotide.

C C

C

OPhosphate

O

CC

O -P OO

ONitrogenous

base

Deoxyribose

Cytosine C Thymine T

Adenine A Guanine G

DNA has four different bases:

Remember, DNA has two strands that fit together something like a zipper.

The teeth are the nitrogenous bases.

• Adenine and Thymine always join togetherA T

• Cytosine and Guanine always join togetherC G

C

C

C

C

N

N

OO

N

C

C

C

C

N N

OO

N

N

N C

The bases attract each other because of hydrogen bonds.

Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.

The sequence of nucleotides in DNA codes for proteins.

1. Assemble one side of your DNA molecule.

2. Match the chemical base pairs.

3. Complete your DNA molecule.

4. Twist your model.5. Label your model.

1

2

3

4

5

Sequence : T A C G T A T G A A A C

During most of a cell’s life, the cell’s DNA is a form called chromatin

Chromatin is loose uncoiled strands of DNA

Before the cell divides; the DNA will wrap itself around proteins to form a chromosome

Our genes are on our chromosomes

A chromosome contains two identical parts called chromatids

The point at which the two chromatids attach to each other is called the centromere

• 2 chromatids = chromosome

Two similar chromosomes

They are the same size, shape, length, and code for the same traits

You get one from your mother and one from your father

Body cells are called somatic cellsSome examples of somatic cells are muscle cells and skin cells

In a somatic cell, you have 46 chromosomes; you have 23 pairs of homologous chromosomes

Sex chromosomes determine your sexXX – FemaleXY – Male

DNA has to be copied before a cell dividesThis happens during the S or synthesis

phase of interphase in the cell cycle

Mitosis-prophase-metaphase-anaphase-telophase

G1 G2

Sphase

interphase

The double stranded DNA is unzipped (breaking the weak hydrogen bonds) to form two single strands, each having the information needed to make a copy of the original.

Each cell has about 2 m of DNA.

The average human has 75 trillion cells.

The average human has enough DNA to go from the earth to the sun more than 400 times.

DNA has a diameter of only 0.000000002 m.

The earth is 150 billion mor 93 million miles from the sun.

Pyrimidines are Pyrimidines are single ring single ring bases.bases.

Purines are Purines are double ring double ring bases.bases.

C

C

C

C

N

N

OO

N

CC

CC

N

N

N

N

N

C

Thymine and cytosine each have one Thymine and cytosine each have one ring of carbon and nitrogen atoms.ring of carbon and nitrogen atoms.

C

C

C

C

N

N

OO

N

cytosinecytosine

C

C

C

C

N

N

OO

OO

thyminethymine

C

AdenineAdenine and and guanineguanine each have two each have two rings of carbon and nitrogen rings of carbon and nitrogen atoms.atoms.

C

C

C

C

N

N

N

AdenineAdenine N

N

C

C

C

C

C

N

N

OO

N

GuanineGuanine N

N

C

When making hydrogen bonds, cytosine always pairs up with guanine,

And adenine always pairs up with thymine.

(Adenine and thymine are shown here.)

C

C

CC

N

N

N

N

N

C

C

C

C

C

N

N

OO

OO

C

Our genes are on our chromosomes.

Chromosomes are made up of a chemical called DNA.

sister chromatid

DNA in Your Cells