Hair Evidence

Warmup

Do you have a cowlick?
(What is a “cowlick”?)

Match the Magnification

4x magnification
red band
shortest objective lens

10x magnification
yellow band
medium length lens

40x magnification
blue band
longest objective lens

Match the Magnification

4x magnification
red band
shortest objective lens

10x magnification
yellow band
medium length lens

40x magnification
blue band
longest objective lens

Use this to get the most details using
the fine adjustment knob

Use to scan your slide for the best part
to sketch; use coarse adjustment knob

Use this if the light and highest power
do not allow for good visual details.

Hair Structure

•You WILL SEE your scales and medulla on high power
(40x) if you focus correctly with your microscopes today!

Hair shape (round or oval) and texture (curly or straight) is influenced heavily by
genes. The physical appearance of hair can be affected by nutritional status and
intentional alteration (heat curling, perms, straightening, etc.).

Sources: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair & http://www.fbi.gov/hq/lab/fsc/backissu/july2000/deedric1.htm#Index%20(Hairs)

Hair is composed of the protein keratin, which is also the primary component of
finger and toe nails.

Hair is produced from a structure called the hair follicle. Humans develophair
follicles during fetal development, and no new follicles are produced after birth.

Biology of Hair

In order to test hair evidence for nuclear DNA, the root must be present. The hair
may also be tested using mitochondrial DNA whether or not the root is present.

Hair Structure

(Draw and color this in your journal)

Hair is composed of three principal parts:

The structure of hair can be compared to that of a pencil with the medulla being the
lead, the cortex being the wood and the cuticle being the paint on the outside.

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Cuticle – outer coating composed of overlapping scales

Cortex – protein-rich structure around
the medulla that contains pigment

Medulla – central core
(may be absent)

Characteristics of the cuticle may be important in distinguishing between hairs of
different species but are often not useful in distinguishing between different people.

Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.hairdressersus.com/micro/Image5b.jpg

Hair Structure
Cuticle
The cuticle varies in:

• Its scales,

How many there are per centimeter, How much they

overlap, Their overall shape, and How much they protrude
from the surface
• Itsthickness, and
• Whether or not it contains pigment.
•You WILL SEE your scales if you focus
correctly with your microscopes today!

Cortex

The cortex varies in:

• Thickness
• Texture
• Color

• Distribution of the cortex is perhaps the most important component in
determining from which individual a human hair may have come.

• Microscopic examination can also reveal the condition and shape of the root
and tip.

Info: http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair Image: http://www.extrapersonality.com/hair.html

Hair Structure

Medulla

The medulla may vary in:

• Thickness
• Continuity - one continuous structure
or broken into pieces
• Opacity - how much light is able to
pass through it

• It may also be absent in some species.

http://library.thinkquest.org/04oct/00206/lesson.htm#t_hair

Like the cuticle, the medulla can be important for distinguishing
between hairs of different species, but often does not lend much
important information to the differentiation between hairs from
different people.

Hair Structure

http://www.bfro.net/images/whatis/figures/Fig.%203%20with%20caption.jpg

It’s time to

examine
some hair
samples!

http://micro.magnet.fsu.edu/primer/techniques/polarized/gallery/images/humansmall.jpg

Follow the steps for using the
microscope from our
microscope lesson!

Only what the pointer is
centered on will be magnified in
the field of view!

Clean Up Time

Properly put away your microscopes - don’t
leave any slides on them.

Put all glue, tape, etc. back in your boxes and
close them

Wipe down your tables with sanitizer paper
towels.

Ticket Out:

What was the
most
surprising
thing you
learned about
hair evidence
today?