Chapter 4 Lesson 2 Notes Inheritance

Modeling Inheritance

– __________________

– __________________

• Two tools can be used to identify and predict traits among genetically related individuals.

4.2 Understanding Inheritance

Heredity

Punnett Squares

• If the genotypes of the parents are known, the genotypes and phenotypes of the offspring can be predicted.

• A ____________ square is a model used to _____________possible ___________and ___________of offspring.

4.2 Understanding Inheritance

One-Trait Model

• The Punnett square shows the possible offspring of a cross between two true-breeding pea plants—one with yellow seeds and one with green.

4.2 Understanding Inheritance

One-Trait Model (cont.)

– The phenotype will be yellow seeds because Y is dominant to y.

– The only possible genotype for hybrid offspring is heterozygous—Yy.

4.2 Understanding Inheritance

Two-Trait Model

• The possible offspring of two heterozygous genotypes—Yy and Yy—would have three different genotypes and two phenotypes.

4.2 Understanding Inheritance

Pedigrees

• All the genetically related members of a family are part of a family tree.

4.2 Understanding Inheritance

• A ___________shows genetic ________ that were ____________ by members of a family tree.

• Pedigrees are important tools for tracking complex pattern of inheritance and genetic disorders in families.

Pedigrees (cont.)

4.2 Understanding Inheritance

A pedigree chart that shows three generations of a family.

Types of Dominance

• Alleles show _____________ dominance when they produce a phenotype that is a _________ of the parents’ phenotypes.

• When both alleles can be ___________ in the ____________ , the interaction is called _________________.

4.2 Understanding Inheritance

– The human blood type AB is an example of codominance.

Multiple Alleles

• Some genes have __________ than _____ alleles, or ____________ alleles.

• The human ABO blood group is determined by multiple alleles as well as codominance.

• There are three different alleles for the ABO blood type—IA, IB, and i.

4.2 Understanding Inheritance

Multiple Alleles (cont.)

4.2 Understanding Inheritance

Sex-Linked Inheritance

• Chromosomes __ and __ are the _______ chromosomes—they contain the genes that determine ___________ or sex.

4.2 Understanding Inheritance

• Except for sperm and eggs, each cell in a male has an X and a Y chromosome, and each cell in a female has two X chromosomes.

• A recessive phenotype is observed in a male when a one-allele gene on his X chromosome has a recessive allele.

Sex-Linked Inheritance (cont.)

4.2 Understanding Inheritance

In this family, the

grandmother’s genome

included the color

blindness allele.

Polygenic Inheritance

• ___________ inheritance is when _________ genes determine the ______________ of a trait.

4.2 Understanding Inheritance

• Many phenotypes are possible when possible when polygenic inheritance determines a trait.

Maternal Inheritance

• Humans inherit mitochondrial genes only from their mothers.

4.2 Understanding Inheritance

• Inheritance of traits related to the mitochondria can be traced from grandmother to grandchildren.

How are the traits of parents inherited and expressed in offspring?

Human Genetic Disorders

• If a change occurs in a gene, the organism with the mutation may not be able to function as it should.

4.2 Understanding Inheritance

• An ___________ ____________ can result in a phenotype called a genetic _____________.

Human Genetic Disorders (cont.)

4.2 Understanding Inheritance

Genes and the Environment

• An organism’s environment can affect its phenotype.

– Genes affect heart disease, but so do diet and exercise.

– Genes affect skin color, but so does exposure to sunlight.

4.2 Understanding Inheritance