Date post: | 20-Jan-2016 |
Category: |
Documents |
Upload: | marion-riley |
View: | 227 times |
Download: | 6 times |
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 flowersCarrier- 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
Aa Aa
aa
aa
AaAa
Aa Aa
aa
Recessive (aa)
AA orAa
Reading a Pedigree• Is this a dominate or recessive disease?• Which individuals MUST be carriers?
-None. Cannot have carries for a simple dominate disease
• What are the possible genotypes for IV-1?
-Aa
aaAA
aa
aa
Aa
Aa Aa
Aa
Dominate (AA, Aa)
• 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
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
• 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.
Section12.2/12.3 When Heredity Follows Different Rules
Complex Patterns of Inheritance
• Incomplete dominance(不完全显性 ):
Appearance of a third phenotype ( P 31
5)– 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: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:Internal Factors:
– Hormones regulate gene expression so a genotype may not express the same phenotype it different individualsHormones regulate gene expression so a genotype may not express the same phenotype it different individuals
– Ex. PeacocksEx. Peacocks