DNA

Deoxyribonucleic Acid

The DNA Connection

• What have you learned about inheritance, DNA, and cell division up to this point?

• How do genes determine the traits of an organism?

Where is DNA?

• Inside the nucleus of a cell.

• Chromosomes are made of DNA.

• Each chromosome contains thousands of genes.

The Importance of DNA

• DNA tells the body how to make proteins.

• Proteins help to determine all of your physical traits.

• Directions for making proteins are found on genes.

What are Chromosomes?

• Chromosomes are dark, rod-shaped bodies found in the cell nucleus.

• Chromosomes are composed mostly of proteins and DNA.

History of DNA

Rosalind Franklin

• Used X-ray diffraction (the way molecules bend X-rays) to determine the structure of molecules.

• One of the photographs suggested that DNA was a helical (spiral) structure.

James Watson & Francis Crick

• Created the double helix model.

• Recognized the ability of DNA to form exact copies of itself.

Structure of DNA(Twisted Ladder – Double Helix)

• Nitrogen Bases

• Sugars

• Phosphates

The Sides of the “Ladder”

• Sugars and phosphates form the “backbone” of the DNA molecule.

• The name of the sugar is DEOXYRIBOSE.

The Rungs of the “Ladder”• The DNA molecule is made

up of four different nitrogen bases.

* Adenine – Thymine* Cytosine – Guanine

• The bases attach to the sugar part of the DNA backbone (sides).

• The order of the bases form a genetic code that specifies what type of protein will be produced.

DNA Replication

How Does it Work?

• DNA molecule “unzips” down the middle into two pieces.

• It breaks apart where the bases are joined.

• Extra bases are made in the cytoplasm.

• These bases pair up with the “free” bases.

• Two new complete DNA molecules form which are identical to the original DNA.