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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
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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
Many inherited disorders in humans are controlled by a single gene Normal Dd Normal Dd PARENTS • Most such disorders are caused by autosomal recessive alleles • Examples: cystic fibrosis, sickle-cell disease D D Eggs Sperm DD Normal d d Dd Normal (carrier) Dd Normal (carrier) OFFSPRING dd Deaf Figure 9.9A
Examples: achondroplasia, Huntington’s disease • A few are caused by dominant alleles Figure 9.9B
Tracking Traits & Prediction • Before mating • Genetic screening - karyotype • Punnets • Pedigree analysis
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 JonathanLambert Dd Elizabeth Eddy Dd Dd dd Dd Dd Dd dd Female Male Deaf Hearing Figure 9.8B
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
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 Fetus(10-12weeks) Several hourslater Placenta Suction Karyotyping Fetal cells(from chorionic villi) Some biochemical tests Chorionic villi Figure 9.10B
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