Human Genetic Disorders Harmful or Beneficial?. Human Genetic Disorders Mutations are key –DNA...
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Transcript of Human Genetic Disorders Harmful or Beneficial?. Human Genetic Disorders Mutations are key –DNA...
Human Genetic Disorders
Harmful or Beneficial?
Human Genetic Disorders
• Mutations are key– DNA change change in alleles
• Chromosomal errors – nondisjunction
– Deletion, inversion, translocation
Disorders may be…
• In germ cells or somatic cells
• Dominant or recessive
• Autosomes or Sex linked
• Most such disorders are caused by autosomal recessive alleles– Examples:
cystic fibrosis, sickle-cell disease
Many inherited disorders in humans are controlled by a single gene
Figure 9.9A
D D
d d
NormalDd
NormalDd
DDNormal
DdNormal(carrier)
DdNormal(carrier)
ddDeaf
Eggs Sperm
PARENTS
OFFSPRING
• A few are caused by dominant alleles
Figure 9.9B
– Examples: achondroplasia, Huntington’s disease
Table 9.9
Tracking Traits & Prediction
• Before mating– Genetic screening - karyotype
– Punnets
– Pedigree analysis
• Family pedigrees are used to determine patterns of inheritance and individual genotypes
Figure 9.8B
DdJoshuaLambert
DdAbigailLinnell
D_Abigail
Lambert
Female
DdElizabeth
Eddy
D_JohnEddy
? D_HepzibahDaggett
?
?
ddDdDdDdddDdDd
MaleDeaf
Hearing
ddJonathanLambert
• Fetal cells can be obtained through amniocentesis
Genetic testing
Figure 9.10A
Amnioticfluid
Fetus(14-20weeks)
Placenta
Amnioticfluidwithdrawn
Centrifugation
Fetalcells
Fluid
Uterus Cervix Cell culture
Severalweeks later Karyotyping
Biochemicaltests
After fertilization• Amniocentesis• Chorionic villi sampling• Protein tests/biochemical tests via urine
samples• Ultrasound (sonogram)
• **Genetic counseling for all**
• Chorionic villus sampling obtains fetal cells for karyotyping
Figure 9.10B
Fetus(10-12weeks)
Placenta
Chorionic villi
Suction
Several hourslater
Fetal cells(from chorionic villi)
Karyotyping
Some biochemical
tests
• Uultrasound (sonogram)
Figure 9.10C, D
Risks to consider:
• Harm to baby– Invasive, risk of miscarriage
• Harm to mother– Invasive, risk of infection
• Ethical, moral, personal decisions