The DNA

Connection Adapted from Prentice Hall: Life

Science Textbook

DNA Tests Set Man Free After 17 Years in Prison: http://www.nbclearn.com/portal/site/k-

12/browse?cuecard=47695

Can You Crack the Code?

Use the Morse code in the chart to decode the question in

the message below. The letters are separated by slash

marks.

•- -/ • • • •/ •/ •- •/ •/

•-/ •- •/ •/-- •/ •/- •/ •/

• • •/ •- • •/- - -/- •- •/ •-

/-/ •/- • •/

Write your answer to the question in Morse code.

Learning Goal Students will be able to understand and identify

important aspects of DNA as well as explain the

purpose of DNA in any living body.

What do you already know about DNA?

DNA: Deoxyribonucleic Acid

• The genetic material that carries information

about an organism and is passed from parent

to offspring.

• The information in DNA also directs all of the

cell’s functions.

Structure of DNA • In 1952 Rosalind Franklin used an X-ray

method to photograph DNA molecules. Her

photographs helped James Watson & Francis

Crick figure out the structure of DNA in

1953.

Structure of DNA • A DNA molecule looks like a twisted ladder, or

spiral staircase. The two sides of the DNA

ladder are made up of molecules of a sugar

called deoxyribose, alternating with molecules

knows as phosphates.

• Each rung is made up of a pair of molecules

called nitrogen bases. Nitrogen bases are

molecules that contain the element nitrogen

and other elements.

DNA Nitrogen Bases • DNA has four kinds of nitrogen bases:

– Adenine (A)

– Thymine (T)

– Guanine (G)

– Cytosine (C)

• The bases on one side of the ladder pair with the bases on the other side.

– Adenine (A) only pairs with thymine (T)

– Guanine (G) only pairs with cytosine (C)

• This pairing pattern is the key to understanding how DNA replication occurs.

What are the structures that

make up a DNA molecule?

Students will be able to understand and identify

important aspects of DNA as well as explain the

purpose of DNA in any living body.

Where are you?

DNA Replication

• During DNA replication, the

two strands in the DNA

molecules separate (unzip),

and then new nitrogen bases

pair up with each strand.

This forms an EXACT replica

of the original DNA strand.

Key Concepts 1. What are the nitrogen bases in DNA?

2. Describe how the nitrogen bases pair in a

DNA molecule.

3. One section of a strand of DNA has the base

sequence AGATTC. What is the base

sequence on the other strand? How do you

know?

So What? What does DNA have

to do with me?

DNA Fingerprinting Unless you are an identical twin, your DNA is unique! Because one person’s DNA is like no one else’s it can be used to produce genetic “fingerprints.” These fingerprints can tie a person to the scene of a crime, just like actual fingerprints! DNA can prevent the wrong person from going to jail. It can also be used to identify skeletal remains. Today, soldiers and sailors give blood and saliva samples so their DNA fingerprints can be saved. Like the identification tags that soldiers wear, DNA records can be used to identify the bodies of unknown soldiers or civilians.

Analyzing DNA In one method of DNA analysis, DNA from saliva, blood, bones, teeth, or other fluids or tissues is taken from cells. Special enzymes are added to

cut the DNA into small pieces. Selected pieces are put into a machine that runs an electric current through the DNA and sorts the pieces by size.

The DNA then gets stained and photographed. When developed, a unique banded pattern similar to a product bar code, is revealed. The pattern can

be compared to other samples of DNA to determine a match.

Limitations of DNA

Fingerprinting Like all technology, DNA fingerprinting has its

limitations. DNA is very fragile and the films

produced can be difficult to read if the DNA

samples are old. In rare instances, DNA from

the people testing the samples can become

mixed in with the test samples and produce

inaccurate results. DNA testing is also time

consuming and expensive.

Historical Uses DNA fingerprinting was invented in 1984 by Professor Sir Alex Jeffreys at the University of Leicester in the United Kingdom.

It was first used in an immigration dispute to prove that a boy returning to the UK from Ghana really was the son of legal immigrants.

In 1987 in Leicester, the first criminal case involving DNA evidence resulted in the conviction of the true murderer and exoneration of an innocent person.

One very interesting use of the technique confirmed that skeleton was the remains of an Auschwitz camp doctor, Josef Mengele, who escaped to South America in 1979. DNA from the skeleton was compared with DNA from Mengele’s wife and son, who were still alive in Germany.

In the News… • DNA Evidence Used to Convict Criminals:

http://www.nbclearn.com/portal/site/k-

12/browse?cuecard=5832

Think About It… Should the United States have a National DNA

Fingerprinting Database?

This would require every citizen to have DNA

samples taken and stored.

What would THEY think?

- Medical insurance companies

- People with genetic disorders

- Judges who try criminal cases

- Victims of crimes in which the criminal was

never identified

- Citizens on both sides of the issue

Summary Take a few moments to collect your thoughts-

write a summary (5-7 sentences) using the

terminology we learned today.

Students will be able to understand and identify important aspects

of DNA as well as explain the purpose of DNA in any living body.

In the next few days…

• Tuesday: Lab 59 – DNA Fingerprinting

Simulations

• Wednesday: DNA Extraction Lab (if you have

long hair bring a pony tail holder!)

• Thursday: DNA Fingerprinting Lab with

Officer Chevy

• Friday: Walking the Track (more info soon) &

finish up DNA week!