At the end of this lesson, I will
be able to
0 Explain how DNA Fingerprinting is related to the
structure of a chromosome
0 Explain how the ability to create a DNA Fingerprint is
based on evolutionary change in the human genome
0 Analyze a gel of DNA Fingerprints to determine
paternity and the guilt/innocence of criminal suspect
Today’s critical vocabulary
0 Chromosome
0 Coding DNA
0 Non-Coding DNA
0 Repeating DNA
0 Homologous pairs
0 Restriction Enzymes
0 Gel 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
Non Coding
DNA
Gene 1
Non Coding
DNA
Gene 2
Non Coding
DNA
Gene 3
Non Coding
DNA
Gene 4
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?
Non Coding
DNA
Gene 1
Non Coding
DNA
Gene 2
Non Coding
DNA
Gene 3
Non Coding
DNA
Gene 4
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.
0 Since this mutation has no effect, these mutations or
variations are passed along to offspring.
Let’s Reflect
What 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 Reflect
Why 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 noncoding 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
0 The section of the chromosome is cut out by the
correct restriction enzyme
0 The sections of DNA are then run through a gel
electrophoresis where DNA fragments of different
sizes are separated
0 The 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 electrophoresis
2. 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.