Cell ProcessesCell ProcessesSUGAR

Phosphate Group

BASE

Looking Inside Cells• Cell Wall• Cell Membrane• Nucleus• Mitochondria• Endoplasmic Reticulum• Ribosomes• Golgi Bodies• Chloroplasts• Vacuoles• Lysosomes

Look Inside a Cell-2Look Inside a Cell-1

Nucleus

• Nuclear Membrane

• Chromatin

• Nucleolus Journey into the Nucleus

D N A• DNA – the blueprint of life

• DNA is a nucleic acid found in the chromatin in a cell’s nucleus

• DNA holds all the information that the cell needs to carry out its functions

• DNA ReplicationDNA Replication– A cell makes a copy of its DNA before

mitosis occurs

– ensures that each replicated cell will have all of the genetic information it needs to carry out its activities Journey into DNA

Why Do We Study DNA

• Central importance to all life on Earth

• Medical benefits such as cures for diseases

• Better food crops.

• Our genes are on our chromosomes

• Chromosomes are made up of a chemical called DNA.

Chromosomes & DNA

DNA-Deoxyribonucleic Acid Made up of nucleotidesnucleotides (DNA molecule) in a DNA DNA

double helix double helix

It looks like a twisted ladder or a spiral stair staircase

NucleotideNucleotide::1. Phosphate groupPhosphate group2. 5-carbon sugar5-carbon sugar3. Nitrogenous baseNitrogenous base

~2 nm wide~2 nm wide

DNA Double Helix

Mitosis Review

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

DNA Building Block

• The backbone of the molecule is alternating phosphates and deoxyribose sugar

• The teeth are nitrogenous bases– Adenine– Thymine– Guanine– Cytosine

phosphate

deoxyribose

bases

Structure of DNA• The two sides of the DNA

ladder are made of molecules of a sugar called deoxyribose nucleic acid- (DNA) --alternating with molecules known as phosphates

• Each rung of the DNA ladder is made of a pair of molecules called nitrogen bases

• Four kinds of nitrogen bases– Adenine - A– Thymine - T– Guanine - G– Cytosine - C

Structure of DNA

DNA Replication Process• DNA replication begins when two

sides of the DNA molecule unwind and separate, like a zipper unzipping

• The molecules separate between the paired nitrogen bases

• Nitrogen bases that are floating pair up with bases on each half of the DNA molecule

• Rules of Pairing:– A always binds with T– G always binds with C

DNA Replication Process

Once bases are attached, two new DNA molecules are formed.

The order of the bases in each new DNA molecule will exactly match the order in the original DNA molecule

Tour of DNA

Interesting DNA facts

• 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.

Extraction of DNA