*Do Now!

*Make sure tonight’s homework is written in your agenda. *Quietly, discuss and respond to the

following questions (answers should be written on your whiteboard). *What is the difference between a trait and a

characteristic? *Where are genes found in cells? *Why is DNA important?

Section 4.1

*What does DNA look like?

*Vocabulary

*DNA- DeoxyriboNucleic Acid, a molecule that is present in all living cells and that contains the information that determines the traits that a living thing inherits and needs to live. *Nucleotide- in a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base.

*What we already know . . .

*As we’ve discussed, inherited traits are determined by genes, and genes are passed from one generation to the next. *Genes are parts of

chromosomes, which are structures in the nucleus of most cells (eukaryotic cells). *Chromosomes are made of

protein and DNA (DeoxyriboNucleic Acid), or the genetic material (the material that determines inherited characteristics).

*Pieces of the puzzle . . .

*While first studying DNA, scientists knew that the material that makes up genes must be able to * (1.) give instructions for building and maintaining

new cells and * (2.) each cell must be copied so that new cells have

the same genetic composition. *NUCLEOTIDES! The subunits of DNA! Nucleotides

make up DNA and consist of a sugar, a phosphate, and a base. *There are four different bases: Adenine (A),

Thymine (T), Guanine (G), and Cytosine (C)

*Understanding DNA . . .

*Biochemist ERWIN CHARGAFF noticed that the amount of adenine in DNA always equals the amount of thymine AND that the amount of guanine always equals the amount of cytosine. These are known as Chargaff’s Rules. *Chemist ROSALIND FRANKLIN

used a process called X-ray diffraction to view DNA. The images she captured suggested that DNA has a spiral shape. *Scientists JAMES WATSON and

FRANCIS CRICK used Franklin’s images to build the first model of DNA.

*DNA’s Double Structure . . .

*A strand of DNA looks like a twisted ladder. This is known as a double helix. *The two sides of the ladder

are made up of alternating sugar and phosphate parts. *The rungs of the ladder are

made up of a pair of bases. *Adenine and thymine always

pair up to make a rung. *Guanine and cytosine always

pair up to make a rung.

*Making copies of DNA . . .

*During replication, a DNA molecule is split down the middle (where the bases meet).*The bases on each side of the molecule

are exposed and new complementary nucleotides are added to each side of the ladder. Then, two DNA molecules are formed (half made up of old DNA and half made up of new DNA). *DNA is copied every time a cell divides. *The job of unwinding, copying, and

rewinding the DNA is done by proteins within the cell. Other proteins help with the process of carrying out the instructions written in the code of the DNA.* http://

www.youtube.com/watch?v=8kK2zwjRV0M

*DNA origami model . . .

*http://www.youtube.com/watch?feature=player_profilepage&v=0jOapfqVZlo*Today, we will be making a model of DNA

using origami. Use the template, instructions sheet, and video to help you. *First, make sure to label the bases (T with

A AND C with G) and color them before folding if using a blank template.