DNA Structure

Where do we get our DNA from?

Structure of DNA Discovered in 1950s by Rosalind Franklin using X-ray diffraction. “Double Helix” term coined by Watson and Crick in the 1950s as well.

DNA is arranged into a ladder-like structure called a Double Helix.

DNA Structure A molecule of DNA is made up of millions of tiny subunits called Nucleotides. Each nucleotide consists of: Phosphate group Pentose sugar Nitrogenous base

Nucleotides Phosphate Nitrogenous Base Pentose Sugar

Nucleotides The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. There are four types of nitrogenous bases.

Nucleotides (Practice) Adenine (Purine) T Thymine (Pyrimidines) C Cytosine (Pyrimidines) G Guanine (Purine)

Nucleotides Each base will only bond with one other specific base. Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Form a base pair. Form a base pair.

DNA Structure Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand. BASE PAIRING IS ALWAYS EQUAL!!!! (Ex: 25% A=25% T)

A C T G G A T C

What do these have in common?

ALL organisms have the SAME components that make up their DNA! Think about the Alphabet...

DNA Structure A gene is a section of DNA that codes for a protein. Each unique gene has a unique sequence of bases. This unique sequence of bases will code for the production of a unique protein. It is these proteins and combination of proteins that give us a unique phenotype.

The purpose of DNA is to help the ribosomes make PROTEIN!!!! Gene Protein Trait The purpose of DNA is to help the ribosomes make PROTEIN!!!!

How are our traits carried on our DNA? Write this down.. How are our traits carried on our DNA?

DNA is copied during a process called replication! What phase of the cell cycle does DNA replication occur? Replication results=one new strand & one original strand

http://www.youtube.com/watch?v=5_vzY7H9GYk&feature=related