DNA Fingerprinting

At the end of this lesson, I will be able to

0Explain how DNA Fingerprinting is related to the structure of a chromosome

0Explain how the ability to create a DNA Fingerprint is based on evolutionary change in the human genome

0Analyze a gel of DNA Fingerprints to determine paternity and the guilt/innocence of criminal suspect

Today’s critical vocabulary

0Chromosome0Coding DNA0Non-Coding DNA0Repeating DNA0Homologous pairs0Restriction Enzymes0Gel Electrophoresis

Simplistic Chromosome Structure

Gene 1

Gene 2

Gene 3

Gene 4

What about the rest of the DNA?

Gene 1

Gene 2

Gene 3

Gene 4

Coding versus non-Coding DNA

Gene 1

Gene 2

Gene 3

Gene 4

Non Coding DNA

Non Coding DNA

Non Coding DNA

Non Coding DNA

Non Coding DNA

A Fingerprint Requires Variation—Where will we find variation in the

chromosome?Discuss with a partner.Come up with a rationale for your answer.

Can you give examples of what happens when there is variation is coding section

of DNA aka a gene?

Gene 1

Gene 2

Gene 3

Gene 4

Non Coding DNA

Non Coding DNA

Non Coding DNA

Non Coding DNA

Non Coding DNA

The variability in the human genome is in the non-coding regions of the chromosome

Since mutations in DNA are TOTALLY RANDOM; occurring equally within coding and noncoding regions;

WHY DO WE SEE SO FEW VARIATIONS WITHIN GENES AND SUCH VARIATION IN THE NON-CODING REGIONS?

The answer is NATURAL SELECTION

0 Individuals who have variations within the coding regions of the DNA that are detrimental are selected AGAINST and do no live to pass that variation on to offspring.

0 Individual who have variations within the non-coding regions have no negative affects. This is an example of a neutral mutation.

0Since this mutation has no effect, these mutations or variations are passed along to offspring.

Let’s ReflectWhat is the primary difference between coding DNA and non-coding DNA?A. Coding DNA is made of all four possible DNA

nucleotides; non-coding DNA contains only three of the possible four nucleotides.

B. Coding DNA is less susceptible to mutation than is non-coding DNA.

C. Non-coding DNA does not contain a sequence that includes instructions for a protein.

D. Coding DNA always stains more darkly than does non-coding DNA.

Let’s ReflectWhy are the DNA sequences of the coding region of DNA maintained generation after generation—even though mutations do occur in these regions?A. The mutations in the coding regions are always

repaired by DNA repair mechanisms.B. Errors or mutations in the coding sections of the

chromosome result in offspring that most likely will not pass the mutation to the next generation.

C. Natural selection corrects any errors that are made in the coding section of a chromosome.

D. Organisms can automatically repair any change in the sequence of the coding region of a chromosome.

Using the Non-coding region to make a DNA Fingerprint

How?1. DNA is sequenced, identifying coding and non-

coding regions.2. Non-coding regions are famous for REPEATING

SEQUENCES OF NUCLEOTIDES.3. One individual may have one nucleotide repeat

(TAA); a second individual may have that sequence repeated 50 times (TAATAATAATAATAA, etc.)

4. This results in different lengths of DNA in the same area of the chromosome

Restriction Enzymes & Gel Electrophoresis

0The section of the chromosome is cut out by the correct restriction enzyme

0The sections of DNA are then run through a gel electrophoresis where DNA fragments of different sizes are separated

0The gel can then be analyzed

From whom do children inherit their noncoding DNA?

How is a crime scene DNA Fingerprint a little different

from a paternity fingerprint?

Who is Johnny’s Daddy?Work with your partner—explain how this is

related to homologous chromosomes.

Personal Reflection

1. Analyze the crime scene gel electrophoresis2. Write one to two sentences explaining how the

bands on this gel are related to the structure of the chromosome using the terms non coding DNA and nucleotide repeats.