Chapter 14.4- Human Traits
·
Pedigree Analysis
o
Family Pedigree- history for a particular trait
and assembling this information into a family tree describing the traits of
parents and children of a certain generation.
o
The figure above shows the pedigree of a family
with a widow-peaked hairline.
o
The importance of a pedigree is to help
calculate that probability of a future child.
o
Pedigrees are more serious when the alleles
could cause a serious disease or disorder
·
Recessively Inherited Disorders
o
Carriers- heterozygotes may transmit the
recessive allele to their offspring
o
Genetic disorders are not distributed among all
group of people
o
When a disease-causing recessive allele is rare,
it is relatively unlikely that two carriers of the same harmful allele will
meet and mate.
o
Cystic Fibrosis- most common lethal genetic
disease in the United States
o
Sickle-Cell Disease- most common inherited
disorder among people of African descent
·
Dominantly Inherited Disorders-
o
Dominant alleles that cause a lethal disease are
much less common than recessive alleles that have lethal effects
o
Huntington’s Disease- a degenerative disease of
the nervous system, is caused by a lethal dominant allele
·
Genetic Testing
o
Avoiding simple Mendelian disorders is possible
when the risk of a particular genetic disorder can be assessed before a child
is conceived
o
Fetal Testing
§
Amniocentesis- tests performed in the 14th-16th
week of pregnancy
§
(CVS)- physician inserts a narrow tube through
the cervix into the uterus and suctions out a tiny sample of tissue
o
Newborn Screening
§
Some genetic disorders can be detected at birth
simply by biochemical tests.
§
(PKU) is the most common newborn screening test.
§
Fetal and newborn screening for serious
inherited diseases, tests for identifying carriers, and genetic counseling.
