Download Chapter12:Patterns of Heredity and Human Genetics

Chapter12:Patterns of Heredity
and Human Genetics
Section12.1 Mendelian
Inheritance of Human Traits
• Interpret a pedigree.
• Identify human genetic disorders caused
by inherited recessive alleles.
• Predict how a human trait can be
determined by a simple dominant allele.
Making a Pedigree
• Pedigree(系谱，P 309)
– A graphic representation of genetic inheritance.
– Track Genotypes by looking at their phenotypes
– Genotype- allele combination for genes that
express a trait (ex. AA, Aa, aa)
– Phenotype- physical traits caused by a
genotype( ex. AA= red flowers, aa= white flowers
Carrier- person who
can pass on a disease
but it not effected by it
Reading a Pedigree
• Is this a dominate
or recessive disease?
• Which individuals
MUST be carriers?
• I-1,2; II-1,2; III-3,4
• What are the
possible genotypes
for III-1?
• AA or Aa
Recessive (aa)
Aa
Aa
AA
or
Aa
Aa
Aa
aa
Aa
Aa
aa
aa
Reading a PedigreeAA
• Is this a dominate
or recessive disease?
• Which individuals
MUST be carriers?
Aa
aa
Aa
-None. Cannot have
carries for a simple
dominate disease
• What are the
possible genotypes
for IV-1?
-Aa
Dominate (AA, Aa)
aa
Aa
Aa
aa
Simple Recessive Heredity
• Recessive traits can
remain dormant and
can appear suddenly;
carriers
• Tend to skip
generations
• Some recessive
disease are fatal and
have late onset
Simple Recessive Heredity
• Cystic fibrosis
disease囊性纤维化
– 1/28 Americans are
carriers
– Thick mucus builds
in the lungs
– Makes physical
activity difficult
– Must be treated with
medication
Simple Recessive Heredity
• Phenylketonuria (PKU)
– Body lacks enzyme to
change phenylalanine to
tyrosine
– Build up in the body
leads to a damaged
nervous system
– Fetuses are tested to
treat with diet
Simple Dominant Heredity
• Heredity of many
physical characteristics
– Widow’s peak hairline
– Darwin earlobes
– Hitchhiker’s thumb
• Traits appear in every
generation and is
equally spread between
males and females
Section12.2/12.3 When Heredity
Follows Different Rules
• Distinguish between alleles for incomplete
dominance and codominance.
• Explain the patterns of multiple allelic and
polygenic inheritance.
• Analyze the pattern of sex-linked inheritance.
• Summarize how internal and external
environments affect gene expression.
Complex Patterns of Inheritance
• Incomplete dominance(不完全显性):
Appearance of a third phenotype （P 315）
– When traits are inherited in an incomplete
dominance pattern, however, the phenotype
of heterozygous individuals is intermediate
between those of the two homozygotes.
Complex Patterns of Inheritance
• Codominance(共显性): Expression of
both alleles（P 316）
– Codominant alleles cause the phenotypes of
both homozygotes to be produced in
heterozygous individuals.
– In codominance, both alleles are expressed
equally.
Complex Patterns of Inheritance
• Multiple phenotypes from multiple alleles
(多重等位基因造成多种表现型，P 317）
– Traits controlled by more than two alleles have
multiple alleles.
Complex Patterns of Inheritance
• Polygenic inheritance(多基因遗传,P 320）
– Polygenic inheritance is the inheritance pattern of a
trait that is controlled by two or more genes.
– Alleles are not dominate or recessive; they represent
degrees of expression
– All heterozygotes are intermediate in phenotype.
Complex Patterns of Inheritance
• Sex determination (性别决定，P318):
– chromosomes, which determine the sex of an
individual, are called sex chromosomes (性染色体).
– 22 other chromosomes are called autosomal
chromosomes (常染色体)。
Complex Patterns of Inheritance
• Sex-linked inheritance(伴性遗传，P 318）
Complex Patterns of Inheritance
• Sex-linked traits(伴性性状，P 319）
– Traits controlled by genes located on sex
chromosomes are called sex-linked traits.
– Red-green color blindness
– Hemophilia
Complex Patterns of Inheritance
• Environmental Factors:
– Temperature, nutrition, light, etc… can effect the phenotype of an
individual by changing the expression of the genes
– Ex. Arctic Fox
• Internal Factors:
– Hormones regulate gene expression so a genotype may not express the
same phenotype it different individuals
– Ex. Peacocks