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 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

A few are caused by dominant alleles Examples: achondroplasia, Huntington’s disease Figure 9.9B

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 Dd Joshua Lambert Dd Abigail Linnell D_ John Eddy ? D_ Hepzibah Daggett ? D_ Abigail Lambert ? dd Jonathan Lambert Dd Elizabeth Eddy Dd Dd dd Dd Dd Dd dd Female Male Deaf Figure 9.8B Hearing

Genetic testing Fetal cells can be obtained through amniocentesis Amniotic fluid withdrawn Centrifugation Amniotic fluid Fluid Fetal cells Fetus (14-20 weeks) Biochemical tests Placenta Several weeks later Figure 9.10A Uterus Cervix Karyotyping Cell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**

Some biochemical tests Chorionic villus sampling obtains fetal cells for karyotyping Fetus (10-12 weeks) Several hours later 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 Harm to mother Invasive, risk of miscarriage Harm to mother Invasive, risk of infection Ethical, moral, personal decisions