Understanding DNA

Deoxyribonucleic Acid

Double Helix: Two strands twisted around each other like a winding staircase

Rosalind Franklin & Maurice Wilkins

James Watson & Francis Crick

very large linear molecules

very large linear molecules

examples: DNA and examples: DNA and RNARNA

examples: DNA and examples: DNA and RNARNA

sugar

phosphate

nitrogen

base

nucleotide

store genetic store genetic information, help to information, help to

make proteinsmake proteins

store genetic store genetic information, help to information, help to

make proteinsmake proteins

Nucleotides A. Sugar (deoxyribose) B. Phosphate Group C. Nitrogen Bases

A

B

C

Erwin Chargaff

A T

C G

Rules for Base Pairing:

B.     Adenine = Thymine (A = T)

A.     Cytosine Guanine (C G)

the lines between the letters are hydrogen bonds

* stores genetic information

What is the function of DNA?

C

G

A

A

T

G

Sugar

Phosphate Nitrogen

Bases

Fun Facts

If you wrote down all of the bases in one cell, you would fill a stack of 1,000 phone books with A's, T's, G's and C's

Fun Facts

If you unraveled all your chromosomes from all of your cells and laid out the DNA end to end, the strands would stretch from the Earth to the Moon about 6,000 times.

DNA Replication

DNA ReplicationResults in two identical DNA

strands 1. DNA helicase separates

or“unwinds” complementary nucleotide strands.

2. DNA polymerases move along each DNA strand adding nucleotides at the replication fork.

3. Each DNA molecule is composed of one old and one new strand.

Errors

DNA polymerases act as proofreaders and make corrections if the wrong nucleotide is added.