Blood, Animal Cells & DNA

Noadswood Science, 2012

Blood, Animal Cells & DNA

To know the composition of blood, animal cells and DNA

Wednesday, April 19, 2023

Animal Cells

A cell is the basic building block for both animals and plants

Cells are extremely small (we need a microscope to see them)

Animal cells have some basic properties (although this is a basic generalisation - we can get extremely specialised cells)

You need to learn the parts which make up our animal cell…

Animal Cell

Animal cells contain: -– Cell membrane– Cytoplasm– Nucleus

Cell membrane

Nucleus

Cytoplasm

Animal Cells

You must also know the functions of the parts which make up the animal cell…

Part Function

Nucleus Controls what happens in the cell (but it is not a ‘brain’)!

Cell Membrane Controls what substances can enter and exit the cell

Cytoplasm Where chemical reactions take place (jelly-like substance)

Traveling

Blood travels through three types of vessel - arteries, veins and capillaries with have specific properties: -

– Arteries are thick-walled muscular tubes which carry blood away from the heart - fast flowing!

– Veins are thin walled tubes which carry blood back to the heart – they have a large diameter and valves as the blood flows slower

– Capillaries are extremely narrow tubes which carry blood through our tissues: their walls are just one cell thick - so thin that oxygen, food and waste products can easily pass through them

Blood

Blood is a liquid tissue whose function is to fight disease and to transport materials around the body

Blood plasma (liquid) containing glucose, amino acids, nutrients, hormones, as well as waste materials like urea Red blood cells contain haemoglobin, a protein which picks up oxygen molecules in the lungs White blood cells fight disease by making antibodies and fighting germs Platelets are cell fragments. Together with fibrinogen they form clots to repair cuts or tears in nearby tissue

Blood Groups

There are 4 main blood groups – A, B, AB and O

The letters refer to antigens on the surface of the red blood cell (a substance which can trigger a response from the immune system)

Blood plasma contains anti-A or anti-B antibodies – if the antibodies meet the specific blood antigen (e.g. anti-A antibodies and antigen A) the blood will clot

Blood Groups

Blood Group Antigens Antibodies

Rh Factor Blood

Many people also have a so called Rh factor on the red blood cell's surface

This is also an antigen and those who have it are called Rh+ and those who haven't are called Rh-

A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance) but a person with Rh-blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies

A person with Rh+ blood can receive blood from a person with Rh- blood without any problems…

Blood groups can be tested for – to identify if it is human, anti-human antibodies can be added to the sample the different antibodies can be mixed to it identifying the blood group…

E.g. anti-A antibodies added to a sample and it clots the blood must be A or AB (if anti-B antibodies are then added and it doesn’t clot it must be group A)

For information (not in exam)!

DNA

The genetic information passed from parent to offspring is contained in genes, carried by chromosomes in the nucleus

All body cells have a nucleus which contains all genetic information

nucleus

DNA

Genes are made up of short lengths of DNA (deoxyribose nucleic acid)

In the 1950’s Watson and Crick were the first to come up with the structure of DNA

DNA is unique (unless you’re an identical twin)

DNA can be extracted from hair, skin flakes, blood, semen and saliva…

DNA

Dead Reckoning

Blood spatter – the use of blood spatter evidence in the trial of Dr. Sam Sheppard in 1955

DNA Profiling

DNA profiling (genetic fingerprinting) is a way of comparing DNA samples to see if they come from the same person…

DNA is taken from a crime scene and compared to a sample taken from suspects / records from the national database

This can also be used for paternity tests as children inherit some of their DNA from mother and father

DNA Profiling

DNA is extracted (blood, semen, saliva etc…) DNA is cut into fragments DNA is separated using electrophoresis (suspended in a gel) DNA is –ve so moves towards the +ve terminal of the gel, and

smaller portions of DNA which have been cut move further than the larger parts

It is then treated to make it more visible…

DNA Crime

A drop of blood was found at a crime scene – DNA profile ran for this and two possible suspects…

Matching DNA samples have the same pattern (suspect 2)…

Unknown DNA from crime scene

DNA Suspect 1 DNA Suspect 2