chapter 12: genetics
DESCRIPTION
Lesson 2: UNDERSTANDING INHERITANCETRANSCRIPT
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CHAPTER 12: GENETICS
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LESSON 2: UNDERSTANDING INHERITANCE
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Essential Questions
What determines the expression of traits?
How can inheritance be modeled? How do some patterns of inheritance
differ from Mendel’s model?
??
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Vocabulary
Gene Allele Phenotype Genotype Homozygous Heterozygous
Punnet square Imcomplete
dominance Codominance Polygenic
inheritance
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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
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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
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Modeling Inheritance Punnett Squares
A Punnet square is a model used to predict possible genotypes and phenotypes of offsprings
Analyzing a Punnet Square
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Modeling Inheritance Using Ratios to Predict Pedigrees
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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
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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
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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
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Classwork
Page 435 #1, 2, 3, 4, 5, 6, 7, and 8
Write down questions and answers
Workbook page 381 - 383