Mendel and the Gene Idea

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12

Many diseases, such as heart disease and cancer, have both genetic and environmental components

Little is understood about the genetic contribution to most multifactorial diseases

Slide 85

Genetic Testing and Counseling

Genetic counselors can provide information to prospective parents concerned about a family history for a specific disease

Slide 86

Counseling Based on Mendelian Genetics and Probability Rules

Using family histories, genetic counselors help couples determine the odds that their children will have genetic disorders

Slide 87

Tests for Identifying Carriers

For a growing number of diseases, tests are available that identify carriers and help define the odds more accurately

Slide 88

Fetal Testing

In amniocentesis, the liquid that bathes the fetus is removed and tested

In chorionic villus sampling (CVS), a sample of the placenta is removed and tested

Other techniques, such as ultrasound and fetoscopy, allow fetal health to be assessed visually in utero

Video: Ultrasound of Human Fetus I

Slide 89

Fig. 14-18

Amniotic fluid

withdrawn

Fetus

Placenta

Uterus

Cervix

Centrifugation

Fluid

Fetal

cells

Several

hours

Several

weeks

Several

weeks

(a) Amniocentesis

(b) Chorionic villus sampling (CVS)

Several

hours

Several

hours

Fetal

cells

Bio-

chemical

tests

Karyotyping

Placenta

Chorionic

villi

Fetus

Suction tube

inserted

through

cervix

Slide 90

Fig. 14-18a

Fetus

Amniotic fluid

withdrawn

Placenta

Uterus

Cervix

Centrifugation

Fluid

Fetal

cells

Several

hours

Several

weeks

Several

weeks

Bio-

chemical

tests

Karyotyping

(a) Amniocentesis

Slide 91

Fig. 14-18b

(b) Chorionic villus sampling (CVS)

Bio-

chemical

tests

Placenta

Chorionic

villi

Fetus

Suction tube

inserted

through

cervix

Fetal

cells

Several

hours

Several

hours

Karyotyping

Slide 92

Newborn Screening

Some genetic disorders can be detected at birth by simple tests that are now routinely performed in most hospitals in the United States