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Molecular Genetics- Chromosomes and
Gene Function
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To introduce genetics
Encourage critical thinking
Introduce the scientific method
To understand the relationship between inherited human diseases, protein structure and
function, and changes in DNA sequences (mutations)
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For example, some say it is a sequence
of DNA that codes for a protein/characteristic
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Two were particularly misleading; Hartsoeker- argued it was a
fully formed male inside a sperm that they saw under a microscope- what he called a ‘homunculus’
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Now we know;
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It all starts from an egg and sperm
You divide to become multicellular
It is cell specialisation and co-operation that allows this
You become complex beings
Cells get nutrients from the environment
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Cells produce waste
Cells use nutrients to assemble the components of the cell e
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proteins
A cell grows bigger until it reaches the critical size
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Each one of these daughter cells take up nutrients and the cycle restarts
Yeast cells do not specialise too much in comparison to animals

The key questions are; how do they know when and how to specialise? And how does a hormone
affect target cells and not other body cells?
o
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Substrate has complimentary site to enzyme active site
They bind
Causes enzyme active site shape to change
An enzyme-substrate complex is produced
New products are formed and released and the enzyme active site returns to its original
shape
The enzyme can be re-used as it is not used up

Cellular Misadventures
E
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1 Sickle Cell Anaemia
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Caused by a mutation in the gene that instructs the body to produce hemoglobin
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Whereas, the amino-acid at the corresponding position in
haemoglobin from sickle cells has an amino-acid that is hydrophobic
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As a result, in sickle cell
anaemia, it changes the shape of erythrocytes from biconcave discs to sickle shaped ones
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g
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g
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Analogies
Music is made of an introduction, chorus and ending
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If a note is replaced by another or an incorrect note is accidently played; we
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sometimes recognise that it is wrong, or we don’t recognise the error, or we recognise the error but
it is minor and negligible
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SIMILARLY, proteins in the body are made of amino acids
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Each protein is made of a different sequence of amino acids
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And if a mutation occurs, sometimes the protein function is compromised and sometimes it is not
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It has an acidic group and base group
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R group= various (20 different types)
An amino acid is amphoteric- has an acid and base group thus can act as an acid or alkali
React in a condensation reaction, water is released and peptide bond is made e
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dipeptide,
tripeptide
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g
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Cystic fibrosis
Cystic fibrosis is a genetic condition in which the lungs and digestive system become
clogged with thick sticky mucus
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This is absent from the membranes of similar cells from cystic fibrosis sufferers
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Forms of interaction between R groups in proteins;
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Disulphide bonds
Ionic bonds
Hydrogen bonds
Van der Walls
Hydrophobic interaction

Examples of proteins
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Intrinsic proteins e
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channel and carrier proteins (completely spans membrane)
Extrinsic proteins (partially spans membrane and is attached on outer side)
Enzymes
Hormones
Collagen
Keratin
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Summary
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Complex things such as organisms start from simple things such as a baby, Lego bricks
buildings
Protein structure and function is pivotal to health
The nucleus houses all genetic information data to form a complex organism

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