Download S1 Unit Two CSI Speyside Revision Notes

The Science behind CSI Speyside
Whilst working together to solve the murder of Ms Wilson you have all learned
some very important Science – here is a summary of all you have learned:
Microscopes:
Scientists use microscopes can be used to view tiny things – such as hairs,
fibres and cells. Stains, like Iodine, can be used to make cells easier to see.
EYEPIECE
LENSES
FOCUS
LIGHT
Onion cells magnified
100 times.
To work out the magnification, multiply the magnification of the lens by the
magnification of the eye piece i.e. 10 x 10 = 100.
Cells:
Plant and animal cells look very different from each other.
Human cheek
cell
Onion skin cell
Plant Cell
Cell wall
Nucleus
Cell
membrane
Vacuole
Cytoplasm
Chloroplast
Animal cell
Nucleus
Cell membrane
Cytoplasm
Part of cell
Job in the cell
Cell
Surrounds the cell, controlling what
membrane
can enter and leave the cell
Cell wall
Surrounds plant cells – makes them
Where this is found
Animal cells
Plant cells
Y
Y
Y
strong.
Jelly-like filling inside the cell –
Cytoplasm
this is where all the chemical
Y
Y
Y
Y
reactions happen in the cell.
Control centre for the cell. Also
Nucleus
stores the chromosomes made of
DNA.
Sap-filled bag in the centre of the
Vacuole
plant cell which helps to make it
Y
strong.
Chloroplast
Used by plant cells to turn sunlight
into food.
Y
Chromosomes, Genes and DNA:
We all look very different from each other – eye colour, hair colour, hair type,
which hand we write with, our fingerprints, etc.
These differences are controlled by chromosomes
which are inherited from our parents.
Chromosomes are found in the nucleus of the cell and
you get half from your mother and half from your
father.
These chromosomes are made of a chemical called DNA (Deoxyribonucleic Acid)
and divided up into sections called genes. Which genes you get will decide what
you look like.
DNA fingerprinting:
DNA can be taken out of the cells and tested to tell who it came from. DNA is
like a code, made up of 4 letters (A, T, C and G), and everyone has a slightly
different version of the code.
When a crime is committed the scientists can collect the DNA and cut it up with
enzymes – rather like special scissors – which cut the DNA every time it sees a
certain combination of letters, e.g. TATC. Exactly where the enzymes cut the
DNA will be slightly different from one person to another.
Scientists can then separate the DNA out by a process called electrophoresis,
where the DNA is put inside a special jelly and electricity is passed through.
The electricity separates out the chunks of DNA – with small bits moving the
furthest. This produces a “DNA fingerprint” – which is unique (unless you have
an identical twin!). Police can then compare the DNA fingerprint from a suspect
Suspect 5
Suspect 4
Suspect 3
Suspect 2
Suspect 1
Crime scene
with the DNA fingerprint found at the crime scene.
This shows the DNA gel being loaded. The picture above shows a DNA
fingerprint from a crime scene. You can match the pattern of lines from the
crime scene with the pattern of lines from the suspects.
Solubility
When you add a solid (e.g. a powder) to water it will either dissolve or not.
When a solid dissolves in a liquid it is called soluble. Solids that do not dissolve
in a liquid are called insoluble.
When a solid dissolves in a liquid it creates a solution. A solution is made up of
the solute (the solid powder) and the solvent (the liquid).
Flame testing:
You can use flame testing to tell different solutions
apart.
Solutions that contain different metals burn with
different coloured flames.
Paper chromotagraphy of inks:
Black ink is made of a combination of several
different coloured inks.
These can be separated using a process called
chromatography.
During chromatography the ink dissolves in
the water (solvent) and moves up the paper.
The different colours separate out and
create a unique pattern for each pen.
What you need to know: