Download I. Types of Genetic Disorders

I. Types of Genetic Disorders
• Sex-Linked Disorders
• Diseases caused by alleles on sex
chromosomes
• Autosomal Dominant
• Diseases caused by dominant alleles
• Autosomal Recessive
• Diseases caused by recessive alleles
• Inbreeding increases chances of offspring
having an autosomal recessive disorder
• Inbreeding: mating of two closely
related individuals
Prefix-Suffix – break it down!
Nondisjunction
• Nondisjunction: homologous chromosomes
fail to separate during meiosis
• If abnormal gamete unites with normal gamete
during fertilization, the resulting zygote will
have an abnormal number of chromosomes
II. Detecting Genetic Disorders
1. Karyotyping
• Analyzes the size, shape, and number of
chromosomes
2. Amniocentesis
• Amniotic fluid, containing
fetal tissue, is sampled and
the fetal DNA is examined
for genetic abnormalities.
3. Ultrasound
• High-frequency sound waves are used to
look at organs and structures inside of the
body.
4. Pedigrees
• Pedigree: a family tree indicating the expression of
a particular trait
• Can be used to determine how a trait is inherited
Key:
• Males = Square
• Females = Circle
• Not shaded – Person does not
carry an allele for a trait
• Half shaded – Person is a
Carrier (only one allele)
• Fully shaded – Person
expresses the trait (two alleles)
III. Examples of Genetic Disorders
1. Sickle-Cell Anemia
• Autosomal recessive
• Result of a point mutation
• Characterized by abnormal hemoglobin which
causes red blood cells to sickle – leading to oxygen
deprivation.
Genotype
SS
Ss
ss
Phenotype
Normal blood
Normal blood; increased resistance to malaria
Sickle cell disease
2. Phenylketonuria (PKU) fen-ul-ke-toe-NU-re-uh
• Autosomal recessive
• Characterized by the inability to break down
phenylalanine (an amino acid)
• Build up of phenylalanine leads to nervous system/brain
damage
• Requires a strict diet
Babies in the United
States and many other
countries are screened
for PKU soon after birth
http://www.ygyh.org/sickle/whatisit.htm
Understanding Rare Chromosome Disorders
https://www.youtube.com/watch?v=k4Lps1kIyR0
3. Tay-Sachs Disease
• Autosomal recessive
• Characterized by inability to break down
lipids.
• Build up of lipids in brain leads to mental
deficiencies, blindness, seizures, etc.
• Common in Ashkenazi Jews
4. Cystic Fibrosis
• Autosomal recessive
• Result of the
deletion of three
bases in a gene
• Characterized by the buildup of thick mucus
that blocks airways and provides breeding
ground for bacteria
5. Huntington’s Disease
• Autosomal dominant
• Characterized by nervous
system damage and
uncontrollable movements
6. Down Syndrome
What is
abnormal about
this karyotype?
• Total # of Chromosomes: 47
• Result of non-disjunction
• Trisomy-21
• Characterized by distinct facial features,
difficulty learning, and other medical
problems (prone to leukemia, Alzheimer’s)
Sex Chromosome Disorders
What sex chromosomes does a typical male have?
What sex chromosomes does a typical female have?
7. Turner’s Syndrome
What is abnormal about this
karyotype?
• Total # of Chromosomes: 45
• Result of non-disjunction
• Absence of a sex chromosome
• Characterized by short stature
and dysfunctional female
reproductive systems
8. Klinefelter’s Syndrome
What is abnormal about this
karyotype?
• Total # of Chromosomes: 47
• Result of non-disjunction
• Extra Sex Chromosome
(XXY)
• Characterized by males with
small testes, problems with
fertility and low testosterone
Genetic Disorder
Pattern of Inheritance
Description
Hemophilia
Sex-linked Recessive
Clotting disorder
(missing proteins)
Colorblindness
Sex-Linked Recessive
Unable to distinguish color
Duchenne Muscular
Dystrophy
Sex-Linked Recessive
Weakening/loss of muscle (missing
proteins)
Sickle Cell Anemia
Autosomal Recessive
Abnormal blood cell shape (oxygen
deprivation)
PKU
Autosomal Recessive
Cannot breakdown phenylalanine
(amino acid)
Tay-Sachs
Autosomal Recessive
Lack enzyme to breakdown lipids for
brain function
Cystic Fibrosis (CF)
Autosomal Recessive
Misfolded protein - build up of
mucus in lungs and body
Huntington’s Disease
Autosomal Dominant
Degenerative disease of the nervous
system
Genetic Disorder
Pattern of Inheritance
Description
Down Syndrome
Nondisjunction
Trisomy – 21: 47 chromosomes
Distinct facial features,
Difficulty learning
Turner’s Syndrome
Nondisjunction
XO – 45 chromosomes
Nondisjunction
XXY – 47 chromosomes
Low testosterone levels,
abnormally small testes
Infertilite
Klinefelters Syndrome