Download video slide - Industrial ISD

Objective 13
TSWBAT explain how
carrier rectognition, fetal
testing and newborn
screening can be used in
genetic screening and
counseling.
Genetic Testing and Counseling
• Genetic counselors can provide information to
prospective parents concerned about a family history
for a specific disease.
• Using family histories, genetic counselors help
couples determine the odds that their children will
have genetic disorders.
• For a growing number of diseases, tests are available
that identify carriers and help define the odds more
accurately.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
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.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Amniotic fluid
withdrawn
Fetal Testing
Centrifugation
Fetus
Fetus
Placenta
Uterus
Placenta
Cervix
Fluid
Fetal
cells
BioSeveral chemical
hours
tests
Several
weeks
Several
weeks
(a) Amniocentesis
Karyotyping
Chorionic
villi
Several
hours
Suction tube
inserted
through
cervix
Fetal
cells
Several
hours
(b) Chorionic villus sampling (CVS)
Newborn Screening
• Some genetic disorders such as PKU can be
detected at birth by simple tests that are now
routinely performed in most hospitals in the
United States.
• PKU cannot be cured but can be controlled by
diet.
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Degree of dominance
Complete dominance Heterozygous phenotype
of one allele
Example
Description
same as that of homozygous dominant
PP
Pp
Incomplete dominance Heterozygous phenotype
of either allele
intermediate between
the two homozygous
phenotypes
C RC R
C RC W C WC W
Codominance
Heterozygotes: Both
phenotypes expressed
Multiple alleles
In the whole population, ABO blood group alleles
some genes have more
IA , IB , i
than two alleles
Pleiotropy
One gene is able to
affect multiple
phenotypic characters
IAIB
Sickle-cell disease
:
Relationship among
genes
Epistasis
Example
Description
One gene affects
the expression of
another
BbCc
BbCc
BC bC Bc bc
BC
bC
Bc
bc
9
Polygenic
inheritance
A single phenotypic
AaBbCc
character is
affected by
two or more genes
:3
:4
AaBbCc