CHAPTER 12: GENETICS
Lesson 2: UNDERSTANDING INHERITANCE
?? Essential Questions What determines the expression of traits? How can inheritance be modeled? How do some patterns of inheritance differ from Mendel’s model?
Vocabulary Gene Punnet square Allele Imcomplete dominance Phenotype Codominance Genotype Polygenic inheritance Homozygous Heterozygous
What controls traits? Chromosomes Genes and Alleles A gene is a section on a chromosome that has genetic information for the trait The different forms of a gene are called alleles
What controls traits? Genotype and Phenotype Geneticists call how a trait appears, or is expressed, the trait’s phenotype The two alleles that control the phenotype of a trait are called the trait’s genotype When the two alleles of a gene are the same, its genotype is homozygous If the two alleles of a gene are different, its genotype is heterozygous
Modeling Inheritance Punnett Squares Analyzing a Punnet Square A Punnet square is a model used to predict possible genotypes and phenotypes of offsprings Analyzing a Punnet Square
Modeling Inheritance Using Ratios to Predict Pedigrees
Complex Patterns of Inheritance Types of Dominance Incomplete Dominance: alleles show incomplete dominance when the offspring’s phenotype is a combination of the parents’ phenotypes Codominance: When both alleles can be observer in a phenotype, this type of interaction is called codominance
Complex Patterns of Inheritance Multiple Alleles Some genes have more than two alleles, or multiples alleles, like human ABO type. Sex-Linked Traits Females have two X chromosomes, males have an X and a Y chromosome Polygenic Inheritance Polygenic Inheritance occurs when multiple genes determine the phenotype of a trait
Genes and the Environment An organism’s genotype determines its phenotype. Scientist have learned that genes are not the only factors that can affect its phenotype An organism’s environment can also affects its phenotype
Classwork Page 435 #1, 2, 3, 4, 5, 6, 7, and 8 Write down questions and answers Workbook page 381 - 383