Transcript Year 10 Genetics Chemical code for life

Year 10 Genetics
Chemical code for life
Chris Willocks 2006
1
History
• In 1953 Watson and
Crick unravelled the
structure of DNA
• Deoxyribonucleic acid
• Double helix
• Controversy of how
results were obtained
2
DNA
• Deoxyribonucleic acid
• Double helix
• Rails are alternating
phosphates and sugars
• Rungs are 4 bases
• DNA is universal -all
living things from bacteria
to humans have the same
4 bases
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Bases
4 bases are:
• Adenine
• Thymine
• Cytosine
• Guanine
Base pairs:
• A-T
• G-C
4
DNA Replication
• DNA is copied before
a cell divides
• DNA unzips
• New nucleotides are
added
• Each new strand is
identical to original
5
DNA and chromosomes
• DNA coils tightly
around proteins
• Like twisting a piece
of string
• See sample DNA
6
Genetic code
• Sections of DNA (up
to 1000 bases) form a
single gene
• Each gene codes for
a protein
• Proteins determine
characteristics such
as eye colour
7
Gene expression
• Genes code for polypeptides
• Polypeptides are made from amino acids
• Polypeptides combine to form proteins
8
Mutations
• A mutation is any
change in DNA or
chromosome that
produces an
alteration in the
characteristic it codes
for
• Occur naturally
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Mutagens
• Mutagens increase the
rate of mutations
• X-rays, UV light,
pesticides, benzene,
Agent Orange
10
DNA mutations
• Some DNA mutations do not cause changes to the
proteins = silent mutation
• Other mutations make major changes to proteins
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Cystic fibrosis
• Most common
inherited disease
• Sufferers have a
missing protein in cell
membranes
• Mucous secretions
are very thick
• Sufferers need
considerable medical
intervention to survive
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Cystic fibrous mutation
• Caused by a single
base deletion in the
DNA
• Causes a frameshift
mutation
13
Down’s syndrome
• Mistake in
chromosome number
• Mistake during
meiosis
14
Down’s syndrome and
maternal age
• Risk of Down’s syndrome increases with maternal age
15
Human Genome Project (HGP)
• Collaborative work
from laboratories
around the world
• The purpose is to
map every gene on
the human genome
• Finished sequencing
the bases in 2000
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Human genome project
Future progress:
1. to identify all the genes
2. Identify mutations and the corresponding
diseases
3. dangerous variations among newly conceived
babies in utero will be predetermined.
4. Will be able to change the harmful traits that
the baby might have so that it will not
encounter any kind of genetic disease
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