Mitochondrial DNA Analysis Used for samples that cannot be analyzed using RFLP or STR

Uses DNA extracted from mitochondrion rather than nuclear DNA

Mitochondrial DNA degrades at a much slower rate than nuclear DNA

Allows analysis of older biological samples, such as hair and bones

Not as precise as STR

Extremely expensive and time consuming

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Oocyte Maturation Mitochondria are the

“powerhouses” of the

cell.

Cellular energy comes

from mitochondira.

Mitochondria have

their own DNA.

Regular DNA - from all of your ancestors.

Mitochondrial DNA is inherited from your

mother ONLY

VNTRs can be used to generate DNA fingerprints

Since some repeated sequences are present at multiple places in genome, a

single probe can detect multiple VNTRs on one genomic Southern blot.

DNA fingerprint = set of VNTR

fragments from an individual’s

genome.

3 separate

VNTR loci

Gel Electrophoresis

- Gel made of agarose forms a matrix.

- Phosphate groups on DNA carry negative charges.

- DNA sample is loading into a well on the gel as shown in A.

- Fragments of the same size will settle at the same location on the gel.

- After applying power, DNA fragments migrate to the positive electrode

- Fragments are separated based on their sizes, smaller fragments moving

faster while larger fragments moving more slowly.

6

DNA Structure

Phosphate groups give

DNA its negative

charge

7

• DNA bands do not have colors.

• Ethidium bromide (a chemical) inserts itself between DNA bases.

• When a gel stained with ethidium bromide is put on a UV table, DNA

bands glow orange light.

• Photography of the gel produces pictures in which DNA bands are

white on a dark background.

• The brighter the DNA bands, the more molecules there are in the

bands.

Sizing

ladders

(standard)

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READING A PROFILE

-The marker column is used to identify strands.

-Each DNA is a vertical line.

-The evidence (on right) was a combination of DNA from 2 people – one male and one female.

-Which Suspect, A or B, was NOT a match?

-Which suspect cannot be excluded from the class of potential perpetrators of this assault?

CQ6. A person has the genotype of 9, 9 on one of his

microsatellite loci. An electrophoresis was conducted

with this DNA. Which lane on the gel below is most

likely the result? (L: size ladder)

L A B C D

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Q – which individual matched the forensic sample?

• STR Data is frequently presented as markers with repeats.

• There are 5 different Loci in the Profile above

• 1- Name one Locus that is homozygous (same marker from

both parents). How many repeats at that Locus?

• 2 - Name one locus that is heterozygous (different markers

from each parent). How many repeats at that Locus?

The following are the results of an analysis on two microsatellite loci

from a mother, a father and their child.

A

B

C

194

198 286

290

290 190 198

190 194

282

286

Locus 1 Locus 2

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• Q – Why can’t person A be the

child of the other two? (Hint: look

at Locus 2)

• Q – Why can’t person B be the

child of the other two? (Hint:

remember what a homozygous

genotype means)

• Q – Which person could be the

child of the other two?

• Q – from this profile, can you tell

which is the mother and which is

the father?

A

B

C

Each test loci is given its own name

D2S1338 FGA CSF1PO

D7S820

D13S317

D16S539 D18S51

D21S11

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Each locus has a unique name

If the repeat section falls within a gene, it has the name of the gene. For example, vWA occurs on the von Willebrand Factor. CSF1P0 is named for the CSF-1 receptor gene. Other loci are named for the chromosome they are on, and the order in which the marker was discovered

How do they get those funny names for CODIS test loci?

• Q – which

chromosome

is D7S820

on?

• Which

chromosome

is D8S1179

on?

• D21S11?

CODIS – the National database for DNA • Contains 2 Parts

• Offenders index- DNA profiles of anyone convicted of sex offenses & other violent crimes

• Forensic index- DNA profiles from crime scenes that have not been matched to a person yet

• Currently uses 13 Loci, but expanding to 20 Loci in 2017 to increase accuracy and match loci used overseas

• Current Loci: Added Loci: Q – based on what you know about CODIS naming, which chromosomes have added loci?

How can DNA evidence be

contaminated?

Sneezing or coughing over evidence

Person touches their mouth, nose or other

part of the face and then touches the area

that may contain the DNA to be tested.

Scene personnel can deposit hairs, fibers,

or trace material from their clothing

Wind can carry in contaminants

DNA Strands

Building block of genetic makeup

A complete copy of an individuals

entire genome exist in nearly

every cell

Each persons genome is made up

of billions of base pairs

Most base pairs are “junk” DNA bsapp.com

• DNA strands

come from the

nucleus or the

mitochondria

Only one-tenth

of a percent of

DNA differs from

one human to

the next

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