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 Allele Phenotype Genotype Homozygous Heterozygous

Punnet square Imcomplete

dominance Codominance Polygenic

inheritance

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

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