Human Genetic Disorders

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Human Genetic Disorders

• Harmful or Beneficial?

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Human Genetic Disorders

• Mutations are key
• DNA change ? change in alleles
• Chromosomal errors ?
• nondisjunction
• Deletion, inversion, translocation

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Disorders may be

• In germ cells or somatic cells
• Dominant or recessive
• Autosomes or Sex linked

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Many inherited disorders in humans are controlled
by a single gene

• Most such disorders are caused by autosomal
  recessive alleles
• Examples cystic fibrosis, sickle-cell disease

Normal Dd
Normal Dd
PARENTS
D
D
Eggs
Sperm
DD Normal
d
d
Dd Normal (carrier)
Dd Normal (carrier)
OFFSPRING
dd Deaf
Figure 9.9A
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• A few are caused by dominant alleles

• Examples achondroplasia, Huntingtons disease

Figure 9.9B
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Table 9.9
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Tracking Traits Prediction

• Before mating
• Genetic screening - karyotype
• Punnets
• Pedigree analysis

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• Family pedigrees are used to determine patterns
  of inheritance and individual genotypes

Dd Joshua Lambert
Dd Abigail Linnell
D_ JohnEddy
?
D_ HepzibahDaggett
?
D_ Abigail Lambert
Dd Elizabeth Eddy
?
dd JonathanLambert
dd
Dd
Dd
Dd
dd
Dd
Dd
Female
Male
Deaf
Hearing
Figure 9.8B
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Genetic testing

• Fetal cells can be obtained through amniocentesis

Amnioticfluidwithdrawn
Centrifugation
Amnioticfluid
Fluid
Fetalcells
Fetus(14-20weeks)
Biochemicaltests
Placenta
Severalweeks later
Figure 9.10A
Uterus
Cervix
Karyotyping
Cell culture
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After fertilization

• Amniocentesis
• Chorionic villi sampling
• Protein tests/biochemical tests via urine samples
• Ultrasound (sonogram)
• Genetic counseling for all

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• Chorionic villus sampling obtains fetal cells for
  karyotyping

Fetus(10-12weeks)
Several hourslater
Placenta
Suction
Karyotyping
Fetal cells(from chorionic villi)
Some biochemical tests
Chorionic villi
Figure 9.10B
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• Uultrasound (sonogram)

Figure 9.10C, D
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Risks to consider

• Harm to baby
• Invasive, risk of miscarriage
• Harm to mother
• Invasive, risk of infection
• Ethical, moral, personal decisions