Transcript File - SCSC Year 10 Science

32.4 Using Biological Techniques
Blood group analysis
Blood group analysis
Most common bodily fluid found at crime
scenes - indicative of violence
Forensic serology – examination and
analysis of blood
• Presumptive tests – is blood present?
• Blood typing methods
• DNA recovery
Blood is the body's transport system
What is “blood”?
Red Blood Cells (RBCs)
•Red blood cells are filled with haemoglobin which
lets the blood cells carry oxygen
•aka erythrocytes
how structure is
related to function
part of blood
function
red blood cells
contains haemoglobin
which combines with
oxygen to form
oxyhaemaglobin
- delivers oxygen to
cells
biconcave shape increases surface area
no nucleus – more room
for haemoglobin
white blood cells
immunity
- phagocytosis
- antibody production
change shape
mobile
Platelets
hemostasis - blood
clotting
Plasma
carries substances
around the body
liquid – can easily
transport substances
Activity 32.4A
Find a labelled diagram of a red blood cell
membrane.
Describe the function of each structure:
Lipid
Carbohydrate
Protein
Glycoprotein
Glycolipid
Antigens and antibodies
• Antigen - A protein marker coating the surface
of a red blood cell (RBC) that can stimulate an
immune response – form an antibody. Can be
A,B or O.
• Antibody – proteins carried in the blood
plasma that react with antigens on the RBCs.
A
A
A
A
A
A
ABO System
In 1901, Austrian biologist Karl Landsteiner discovers
ABO blood groups.
•
•
•
•
A antigens = blood type A
B antigens = blood type B
AB antigens = blood type AB
No antigens = blood type O
Rhesus System
In 1940, Landsteiner and Alexander Wiener discovered
another antigen in the blood of rhesus monkeys.
•
85% of the human population have this antigen too
(Rhesus Positive)
•
15% don’t have it (Rhesus Negative)
A person may have
these antigens on
their red blood cells:
This person will have Their blood type is:
these antibodies in
their blood plasma:
A
anti-B
A
B
anti-A
B
A+B
none
AB
none
anti-A + anti-B
O
groups are determined by the A and B markers
on the surface of the red blood cell (antigens)
Rhesus (Rh) is another marker (+/-)
antibodies and antigens are called agglutinins and are found in the blood
– if someone is given the wrong type of blood, clumps form - agglutination
If antibodies bind to antigens on the surface
of red blood cells, the cells clump together.
Reaction
Reaction
with anti-A with anti-B
antibody
antibody
Blood
Group
Antigens
A
A
Yes
No
B
B
No
Yes
O
None
No
No
AB
A&B
Yes
Yes
donated blood is tested for blood group so it
can be matched and used in blood transfusions
32.4 Using Biological Techniques
Skeletal physiology
Why study bones?
• Bones often survive decay and provide the main
evidence for the human form after death.
• Forensic anthropology - the identification of skeletal,
badly decomposed, or otherwise unidentified human
remains.
• Forensic anthropology can suggest the age, sex,
ancestry (race), and stature (height) from the skeleton.
Inventory and Profile
• The Forensic Anthropologist will make a
complete inventory of the bones
received.
• Generalized, non-specific words such as
"cranium" are not used; rather, the
specific bone that is present is described.
• If three bones of the skull are present,
each will be identified – eg the left
parietal, the occipital, and the right
mastoid
• If the skull is complete, that would be
stated.
Race
• Discriminate Function Analysis can identify racial
ancestry from cranial measurements
Black
Caucasian
“Mongol”
Gender
• In order to determine sex, need to know the race. But in order
to determine the race, we need to determine the sex.
• In direct observation, a trained eye can separate male from
female using parts of the skull and the pelvis.
Male
Female
Skull size
Larger
Smaller (~10%
less)
Eye ridges
Prominent
None
Eye sockets
(orbits)
Square
Round
Jaws (mandibles)
Wide
Narrow
Chin
Thick and square
Thin and pointed
Activity 32.4D
•Forensic Scientists can use the pelvis to identify
the sex of human remains.
• Your job is to research the difference between the
male and female pelvis.
•Find diagrams and pictures of the pelvis for both
sexes, label them and record differences in a table.
32.4 Using Biological Techniques
Hairs and
Fibres!
Why study hair?
• The scientific study of hair is called trichology
• Chemical - use of illegal drugs, to screen for the
presence of heavy metals in the body, and to test for
nutritional deficiencies.
• Biological - The root of the hair has cells that contain
DNA, which can be used for DNA analyses.
• Physical - Microscopic comparison of hair collected
from different places can determine if the hairs are
from the same person / animal.
• Primary transfer - the presence of a specific person's
hair can link a suspect or a victim to a crime scene.
You lose ~100 head hairs per day. These usually
end up on clothing, furniture, etc.
• Secondary transfer – moving hair from one place to
another. Common with animal hairs found on pet
owners and in the environment of pet owners.
The Hair fibre
• Cuticle – hard outer
protective layer
• Medulla – soft centre
• Cortex – surrounds
the medulla and
comprise a bulk of
the hair. Contains
pigments.
Hair morphology
There are 6 classifications of human hair:
1. head hair,
2. eyebrow and eyelash hair,
3. beard and moustache hair,
4. body hair,
5. pubic hair,
6. auxillary hair.
• Biochemical studies show that there are no significant
differences in chemical structure among the hair
types.
Microscope analysis
• Hair can be analysed for length, shape, size, colour, stiffness,
curliness, pigmentation, and the appearance of the medulla.
• Complications with the assignment of race involve analysis of
hair from infants and from people of mixed race.
Curliness
Crosssection
Pigment
granules
Other
European
Straight or wavy
Asian
Straight
African
Curly or kinky
Round or Oval
Circular
Oval
Medium-sized
with even
distribution
Medium-sized
grouped in
patches
Large and
clumped in
groups
-
Thick cuticle
Hair shaft twisted
and buckled