Learning
Question
What is a genetic
disorder?
Success Criteria
• State what a mutation is and give
examples of mutagenic agents
• Explain what down’s syndrome is
• Explain and describe how a person can
inherit cystic fibrosis
What is a genetic mutation?
• A mutation is a change in the DNA of a cell
• Mutations are random and can occur in all
organisms
What causes a genetic mutation?
• Genetic mutations are caused by mutagenic
agents that alter the correct sequence of DNA
• Mutations may have no effect
– For example, the protein that a mutated gene
produces may work just as well as the protein from
the non-mutated gene
• Mutations may sometimes be helpful but they
are often harmful
– For example, haemophilia is an inherited disorder
that stops blood from clotting properly
– It is caused by a mutated gene
What do mutations result in?
Sometimes these changes can be so
severe that the cell dies or can divide
uncontrollably and become cancerous
Mutagenic Agents
• Mutagenic agents include UV light, X-rays &
mustard gas
What do mutations result in?
If mutations occur in our sex cells
there is the possibility that the
changes in the gene will be passed onto
the next generation
Genetic Mutations
• In humans, if an egg with two copies of
chromosome 21 is fertilised by a
normal sperm cell then the individual formed
has three copies of chromosome 21 in their
cells
– Such individuals show Down's syndrome
Genetic Mutations
In humans, if an ovum with two copies of
chromosome 21 is fertilised by a normal
sperm cell then the individual formed has three
copies of chromosome 21 in their cells
Egg
Sperm
Such individuals show Down's syndrome
Genetic Mutations
• Down’s syndrome results from having an extra
chromosome 21 and is an inherited disorder
http://www.youtube.com/watch?
v=XGZnO5Im5bM
Genetic Mutations
Cystic fibrosis is caused by inheriting a recessive
CF gene from both parents
Genetic Mutations
• Cystic fibrosis is an inherited
disorder that affects the cell
membranes, causing the
production of thick and sticky
mucus
• It is caused by
a recessive allele
• This means that the recessive
allele must be inherited from
both parents
http://www.youtube.com/watch?
v=WuI72eMrIQI&list=PLJBkk1
http://www.youtube.com/watch?
v=4p1ZihXb29U
1.
2.
3.
4.
What is a mutation?
Name 3 examples of mutagenic substances.
Describe how a mutation be passed on.
Name a disease that can result from genetic
mutation.
5. Describe how someone inherits Down Syndrome.
6. Describe how someone inherits Cystic Fibrosis.
7. What is the chance of a child having cystic Fibrosis
if both parents are unaffected but are carriers of
the recessive allele (heterozygous)
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