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Lecture 2

PHYS-3306EL Lecture Notes - Lecture 2: Linear Energy Transfer, Organ Donation, Apoptosis

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K.Leszczynski, D.Boreham

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Ionizing radiation
o High frequency
o Examples
Gamma rays
Cosmic rays
o Particulate radiation
Some examples
Alpha particles
Beta particles
Heavy, charged ions
o Electromagnetic radiation
Ultraviolet radiation
Gamma rays
X-ray/γ-ray absorption
o Photoelectric effect
Low energy range
Electron emitted
X-ray emitted
o Compton scattering
High energy range
Electron emitted
Scattered photon
o Largest known molecule
o Double helix
o 1 m per cell
o Enough in one person for 365 round trips between the earth and the sun
o Very few changes needed to cause cancer
DNA is an important target for radiation.
o DNA determines what the cell does.
o Destroying the DNA can kill the cell.
o Number of base pairs in half a genome
Number of base pairs in a sperm cell
Number of base pairs in an egg cell
Human genome
o 3.2 billion nucleotides
o Haploid nucleotides
o 23,000 genes
Only one gene needs to be defective to cause serious problems.
o 100,000 proteins
o Different genomes (different people) are approximately 99.5% identical to each other.
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Now slightly less than previously thought
Because better technology is finding subtle differences that were
previously unknown
Approximate sizes
o Red blood cell
8 µm
o X chromosome
7 µm
o Yeast
3 x 4 µm
“’Sugar fungus that makes beer’ – that’s its Latin name, my favourite little
organism in the whole world.”
Human Genome Project (HGP)
o Sequencing the human genome
Finding out what the DNA in a human means
o Funded by the U.S. Department of Energy
To see if any employees had genetic mutations that make them more sensitive
to radiation
o Expensive
$3 billion to sequence one human genome
o Took 13 years to sequence one human genome
Human genome competition
o The first company to sequence 10 genomes in 10 days will get a monetary prize.
$1 million?
Watson’s genome
o Dr. Watson had his genome sequenced.
Took 2 months
Cost $1 million
On 2 DVDs
Almost whole genome made available to the public
One gene not made available to the public
Apolipoprotein E gene
o Predisposes an individual to developing Alzheimer’s disease
Dr. Watson did not want to know the status of his Apolipoprotein E
Said that his DNA was superior to African Americans’ DNA and was fired for
U.S. laws concerning genome sequencing
o Each individual has the right to not know his genome.
o Illegal to take a blood sample (or any other sample) and map the genome without the
individual’s consent for genome sequencing
The chance of being diagnosed with cancer has increased, but the rate of curing cancer has
not changed.
o Concern of over-diagnosis of cancer
Lots of gene mapping can be done before birth.
o Ethical and moral implications
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