genetics

http://www.youtube.com/watch?v=B_PQ8qYtUL0

DNA

• Deoxyribonucleic acid

• Located in the nucleus

• Instructions for how to

make proteins

Watson & Crick

Determined the shape/structure of

DNA in 1953

Rosalind Franklin

• X-ray Crystallography

Structure

• Scientists James Watson and Francis Crick developed a three dimensional model of DNA

• This model of DNA consisted of two strands which were wound around each other like a twisted ladder. This structure is known as a double helix

Every living thing has

DNA.

That means that you have

something in common with a zebra, a tree, a mushroom and

a beetle!!!!

• Three critical things genes need to do:1.) genes need to carry information from

one generation to the next

2.) put that information to work by determining the heritable characteristics of organisms

3.) genes need to be easily copied

DNA is like a fingerprint because everyone’s is a little

different!

How would the police look at DNA to figure out who committed a crime?

You can tell people apart by their fingerprints………

and their DNA!

PUT ON YOUR SCIENCE EYES!

A. DNA is made of chromosomes that are contained inside the nucleus of a cell.

C.

DNA makes up the membrane surrounding a cell’s nucleus.

B. A cell’s nucleus contains the chromosomes which are made of DNA.

D.

Chromosomes make up DNA that is contained outside the cell’s nucleus in the cytoplasm.

Which statement reflects the correct relationship between the nucleus, the cell, chromosomes, and DNA?

SO WHAT IS DNA?PLEASE COPY THIS CHART

INTO YOUR NOTES

DNA

NUCLEOTIDE

4 BASES

DOUBLE HELIX

DNA stands for:D: DeoxyriboseN: NucleicA: Acid

DNA is too small to see, but under a microscope it looks like a twisted up ladder!

What is DNA? DeoxyriboNucleic Acid

* A molecule of nucleic acids that carries genetic information.

* 2 strands twisted around each other called a “double helix” (twisted ladder)

* Each strand is made of linked nucleotides.

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Made up of

nucleotides –

•sugar

•phosphate

•nitrogen base

What is a Nucleotide?

* A subunit of DNA made of 3 parts:

* 5-carbon sugar (deoxyribose)

* phosphate group

* nitrogenous base (there are 4)

DRAW THIS NUCLEOTIDE

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

 Structure of DNA

The nucleotides are made up of:

•deoxyribose(sugar)

•phosphate group

• nitrogen bases-4 types1. Adenine- A

2. Guanine-G3. Cytosine- C

4. Thymine-T

Adenine

(A)

Thymine (T)

Cytosine (C)

Guanine (G)

WHAT ARE THE 4 BASES?

5

adenine

deoxyribose

PO4

What is the structure of DNA?

* The sides (backbone) are made of sugars and phosphates held together by a strong chemical bond.

* The rungs (steps) are paired nitrogenous bases held together by a weak hydrogen bond.

How are the Bases paired?

* Adenine pairs w/Thymine (A-T)* Guanine always pairs w/Cytosine

(G-C)* This is called complementary

pairing. They fit like puzzle pieces.

* Allows the DNA to be replicated (copied).

TA G C

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

PO4

2-stranded DNA 9

sugar-phosphatechain

bases

THE DOUBLE HELIX

14

TIME TO MAKE A DNA MODEL!!!

Left Hand Assignment: DNA StructureGlue the DNA strand and use the following instructions to color the

double helix. Write and answer the questions when you are finished

DNA Coloring Instructions

• Color the deoxyribose sugars green.

• Leave the phosphate groups white.

• Color the nitrogen base adenine orange.

• Color the nitrogen base thymine light blue.

• Color the nitrogen base cytosine red.

• Color the nitrogen base guanine yellow.

DNA Structure Analysis1. The twisted ladder structure of DNA is

called a ________________.

2. The backbone of DNA is made up of _______________________.

3. The ladder-like rungs of DNA are made up of _________________.

4. Adenine always pairs up with __________.

5. Cytosine always pairs up with _________________.

6. A nucleotide is the basic building block of DNA. A nucleotide is made up of one ___________, one ________, and one___________.