Question: Why don’t we all look alike?

DNA – The Code for Life

Characteristics of Living Things

All living things reproduce…

All living things have DNA…

We have been told that DNA is the blueprint for life, BUT what

does that mean?DNA holds the instructions that tell a cell how to construct amino acid chains.

SO WHAT?That is important because amino acid chains build proteins.

ANDProteins build cells

We do not look alike because we all have different DNA or genes. We got half from our mom and half from our dad. How did this happen? This is what we are going to answer.

Gene: segment of DNA on your chromosomes that determines your traits.

Trait: characteristics about you. It can be a body part or a behavior. You inherited your traits from your parents.

DINO DNA!!!

DNA

DNA stands for –Functions of DNA:1. Carries the codes to make proteins.

Deoxyribonucleic acid

2. Carries the genetic material that is passed on from the parents to the offspring.

Discovery of DNA

Rosalind Franklin - Invented X-ray diffraction photography. Photo used to determine the shape of DNA is spiral.

DISCOVERY OF DNA

James Watson and Francis Crick used the information from Franklin and other scientists to build a 3-D model of DNA.

Won the Nobel Peace

Prize in Chemistry in

1961.

Structure of DNA

Shape of DNA - Like a twisted rope ladder.

This shape is called Double Helix.

A single spiral would be called Helix.

STRUCTURE OF DNASide Pieces (The Rope Part)

Are alternating units of a 5 carbon sugar and a phosphate group. These go down both sides of the molecule

phosphate

Sugar (called deoxyribose)

STRUCTURE OF DNANitrogen Bases (Steps of the ladder) -

The bases are connected to the sugar only !!!!!

1. Adenine – A2. Thymine – T3. Cytocine –

C4. Guanine - G

STRUCTURE OF DNA

The nitrogen bases fit together in this way:

Adenine always goes with Thymine

Cytosine always goes with Guanine

The bases are held together by a weak hydrogen bond. Two (2) bonds between A and T, three (3) bonds between C and G.

STRUCTURE OF DNA

These three parts form the basic unit of DNA called the NUCLEOTIDE.

phosphate

Sugar(deoxyribose)

Nitrogen baseCan be A, T, C or G

STRUCTURE OF DNA

The nitrogen bases fit together in this way:

Adenine always goes with Thymine

Cytosine always goes with Guanine

The bases are held together by a weak hydrogen bond. Two (2) bonds between A and T, three (3) bonds between C and G.

STRUCTURE OF DNA

One complete turn of the

double helix is 10 base pairs or 10 steps on the

ladder

phosphate

sugar

thymine

adenine

cytocine

guanine

How does DNA copy itself?

Purpose: DNA copies itself to ensure that each new cell that is produced gets the correct number of chromosomes and receives an EXACT copy of the DNA molecule.

This is called DNA REPLICATION.The DNA molecule serves as its own pattern or template so as an exact copy can be made.

STEPS OF DNA REPLICATION

1. DNA untwists and unzips down the hydrogen bonds. This is why the bonds had to be WEAK.

2. New nucleotides fill in the naked ends produced by the unzipping process.

3. Nucleotides continue to fill in until the entire strand is complete.

4. This results in 2 new identical DNA molecules.

DNA REPLICATIONWhat if there is a mistake?

There is always a chance that the wrong nucleotide bonds to another. HOWEVER, DNA has a special enzyme that is responsible for “reading” the bases and recognizing and replacing damaged or wrong nucleotides. This PROOFREADING allows for only one (1) error in ONE BILLION nucleotides.

Replication #1

Replication #2

Bellringer #8

1. The complimentary strand of DNA to A-G-G-T would be:a) B-H-H-Ub) T-C-C-Ac) A-G-G-Cd) G-A-A-C

2. The side pieces of DNA are made up of:a.Thymine and Adenine c. Phosphate and sugarb.Guanine and Cytosine d. Sugar and a base 3. DNA has two functions. One of those functions is:To carry codes to make proteins. c. To pass on birth defects.To turn in a spiral shape. d. To create new organisms.