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 Aa aa Aa aa Recessive (aa) AA or Aa

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 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

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 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: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 individuals –Ex. Peacocks