1. B2.7 Genetic disorders

2. B2.7 Genetic disorders
Inherited disorders:
Polydactyl
Cystic Fibrosis (CF)
Huntington’s disease

3. You are the result of two things...
and
Key words
Gene
Genetic diagrams
Genetic disorders
Inherited
Dominant
Recessive
Alleles
Polydactyl
Cystic fibrosis
Monohybrid crosses
Homozygous
Heterozygous
Phenotype
Genotype
Stem cells
Embryos

4. Polydactyl
Polydactyly – having extra fingers or toes – is caused by a
dominant allele of a gene and can therefore be passed
on by only one parent who has the disorder

5. Polydactyl

6. Polydactyl
p p
P
p

7. Polydactyl
p p
P Pp Pp
p pp pp

8. Cystic Fibrosis
This is a disorder of cell membranes. It is caused by a recessive
allele so must be inherited from both parents. The parents may
be carriers of the disorder without actually having the disorder
themselves.

9. Cystic Fibrosis
Digestive system
Thick sticky mucus in
pancreas prevents
enzyme release.
Food not digested
properly.
Respiratory System
Thick sticky mucus
blocks passageways
in the lungs.
Breathlessness and
respiratory diseases.

10. The faulty allele is recessive (f)
An individual with one recessive allele is a carrier
An individual with two recessive alleles has cystic fibrosis
Cystic Fibrosis

11. F f
F
f
Cystic Fibrosis
The faulty allele is recessive (f)
An individual with one recessive allele is a carrier
An individual with two recessive alleles has cystic fibrosis

12. F f
F FF Ff
f Ff ff
Cystic Fibrosis
The faulty allele is recessive (f)
An individual with one recessive allele is a carrier
An individual with two recessive alleles has cystic fibrosis

13. What is the chance of two carriers having a child with CF?
F f
F FF Ff
f Ff ff
Cystic Fibrosis
The faulty allele is recessive (f)
An individual with one recessive allele is a carrier
An individual with two recessive alleles has cystic fibrosis

14. What is the chance of two carriers having a child with CF?
F f
F FF Ff
f Ff ff
Cystic Fibrosis
The faulty allele is recessive (f)
An individual with one recessive allele is a carrier
An individual with two recessive alleles has cystic fibrosis
1 in 4 or 25% or 0.25

15. Symptoms
Loss of muscle control
Forgetfulness
Loss of understanding
Huntingdon’s Disease
individual with one
dominant alleles has
Huntington's Disease
Faulty allele is dominant

17. What can science
do about
genetic disease?
GENETIC TESTING
• adults, fetuses or embryos
• remove a cell
• test for disease causing allele
• adults may choose
not to have children
• termination of
fetus with disease
PRE-IMPLANTATION
GENETIC DIAGNOSIS
• fertilisation takes place in lab
• remove a cell from
8 cell embryo
• test for disease
causing allele
• only implant embryo
without disease
GENE THERAPY
• could be used to cure
genetic disease eg CF
• make lots of copies of
normal allele
• put alleles into virus
• virus 'infects' bone marrow cells
• genetically modified cells placed back inside body

18. CLONING
stem cells
unspecialised cells can
become any type of cell
could be used to treat
human illness - 'theraputic
cloning'
some organisms
clone themselves
eg spider plants
genetically
identical
differences
caused by
environment

19. Some of the issues...
Should we test fetuses for genetic disorders?
Are you worried about employers or insurance
companies knowing your genetic information?
Is it ethical to terminate a fetus?
Is gene therapy playing God? Would you think so if
it could cure you of a terminal illness?
is cloning animals acceptable?
How about humans?
Why? why not?