GENETIC DISORDERS &
DISEASES
Types?
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Dominant
Recessive
Sex Linked
Chromosomal
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Mutagens?
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In some genetic conditions, inheriting just one copy of the
mutated gene is enough to cause the disease
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These are called dominant genetic disorders; the
abnormal gene dominates no matter what the second
copy of the gene is.
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If gene is not inherited, can not be passed to children
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Recessive Genes can be passed on even if the parent
did not have the condition
Huntington’s Disease
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Progressively damages the brain and central
nervous system
Symptoms do not usually appear until middle age
Problems?
Passed on by this point…
1 in 2 chance of inheriting the disease
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Some dominant conditions vary in severity form
person to person
Some are affected while others only mildly so or
more strongly expressed; Variable Penetrance
Examples of Dominant Singe Gene disorders:
- Adult polycystic kidney disease
- Huntington’s disease
- Cleft chin
- Phenylketonuria
- Neurofibromatosis
- Achondroplasia
Recessive Inheritance Pattern
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In order to have the disease, one would have to
inherit two copies (alleles) of the abnormal gene,
one from each parent
Cystic Fibrosis
Thalassemia; Alpha & Bata, Sickle-Cell
Albinism
Recessive Genes
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Can be passed down form generation o generation
by people who carry one normal & one copy of
gene
Often unaware of carrying gene
Once two carriers have a child, condition emerges
in the baby
¼ chance child will be born with the disease
Sex-linked Conditions
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Fragile X Syndrome
Hemophilia
Duchene Muscular Dystrophy
Color-blindness
Hairy ears
Chromosome Disorders
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Abnormalities in the normal group of 46
chromosomes that we inherit form parents
More or fewer chromosomes?
Structural Changes?
Trisomy's?
Down’s Syndrome?
Klinefelter’s Syndrome
Cri du Chat (cat’s cry) Syndrome
Williams Syndrome
Pregnant mother may be referred for
screening if:
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Already has a child with an inherited genetic
condition
There is or may be a genetic condition in her or the
fathers family
She or the fathers belong to an ethnic community in
which particular conditions are more common:
Thalassemia (Pakistani/Indian)
Sickle Cell Anemia (African/Caribbean)
Tay-Sachs Disease (Certain Jewish)