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