What do you think this is a model of and why? Ms. Mezzetti Lynn English High School Science Department.

What do you think this is a model of and why?

Ms. MezzettiLynn English High School

Science Department

Describe the basic structure (double helix, sugar/phosphate backbone, linked by complementary nucleotide pairs) of DNA Describe its function in genetic inheritance

DNA DNA is often called the blueprint of life..DNA contains the instructions for making proteins within the cell.

The main role of DNA in the cell is the long-term storage of informationit contains the instructions to construct other components of the cell, such as proteins and RNA molecules.The major function of DNA is to provide the code for the making of proteins.

We study DNA for many reasonsall living organisms contain DNA.its 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 DNA.DNA is located in the nucleus.

Rosalind Franklin took diffraction x-ray photographs of DNA crystalsShe died from cancer before she could publish her findings

In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-raysSome say they took credit for work they stole from FranklinTheir original model was a single strand.

A DNA nucleotide is made up of three parts

5 C Sugar-DeoxyribosePhosphate group Nitrogenous base

DNA is a very long polymer.The basic shape is like a twisted ladder or zipper.This is called a double helix.

A backbone of alternating sugar and phosphate groupsCovalent bonds between nucleotidesThe teeth are nitrogenous bases.

phosphate

deoxyribose

bases

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

• Each strand is held together with hydrogen bonds between the nitrogen bases.

A-Adenine T-ThymineG-Guanine C-Cytosine

DNA has four different bases:

Video: Breaking the CodeVideo: Breaking the Code

PyrimidinesPyrimidines are are single single ring bases.ring bases.

PurinesPurines are are doubledouble ring ring bases.bases.

C

C

C

C

N

N

OO

N

CC

CC

N

N

N

N

N

C

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

C

C

C

C

N

N

N

AdenineAdenine N

N

C

C

C

C

C

N

NOO

N

GuanineGuanine N

N

C

Cytosine always pairs up with guanine

Adenine always pairs up with thymine

The bases attract each other because of hydrogen The bases attract each other because of hydrogen bonds. Hydrogen bonds are weak bondsbonds. Hydrogen bonds are weak bonds

T A

G C

Complementary base pairsComplementary base pairsHydrogen bonds

PURINETWO RINGS

PYRIMIDINEONE RING

Purines and pyrimidines alternate along the double helix

Complementary base pairs adenine + thymineguanine + cytosine

•The ratio of A to T and C to G equals 1:1

Complementary Base PairsA - T + C - G

Apple in the Tree Car in the Garage

Complimentary base pairs are lined up in the middle of the double helix. The hydrogen bonds that hold them together will break during replication and transcription.

A C G T T C G A G G C T A A C G T

A C G T T C G A G G C T A A C G T

T G C A A G C T C C G A T T G C A

Each cell has about 2 meters 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.

What is the role/function of DNA?

Where is DNA located?

What are the three molecules the make up a nucleotide?

What are the four bases?