2Chapter Menu Lesson 1: Foundations of Genetics Lesson 2: Understanding InheritanceClick on a hyperlink to view the corresponding lesson.
34.1 Foundations of Genetics hereditygeneticsdominantrecessivegenelaw of segregationlaw of independent assortmentallelephenotypegenotypehomozygousheterozygous
4Early Ideas About Heredity 4.1 Foundations of GeneticsEarly Ideas About HeredityCombined genetic material from a sperm and an egg determines the traits or features of an offspring.Heredity is the passing of traits from parents to offspring.
5Early Ideas About Heredity (cont.) 4.1 Foundations of GeneticsEarly Ideas About Heredity (cont.)The idea of blending inheritance is offspring are a blend of genetic material from both parents.The genetic material mixed or blended like colors of paint.Over many generations, populations would eventually look alike.Blending inheritance cannot explain why some traits skip a generation.
6Gregor Mendel and His Experiments 4.1 Foundations of GeneticsGregor Mendel and His ExperimentsGregor Mendel was the first to record evidence that traits are determined by factors passed from parents to offspring.Mendel established the basic laws of heredity.Genetics is the study of how traits of organisms are passed from parents to offspring.
7Mendel’s Experimental Methods 4.1 Foundations of GeneticsMendel’s Experimental MethodsMendel conducted breeding experiments by studying seven traits of pea plants and each traits had only two variations.
8Controlled Experiments 4.1 Foundations of GeneticsControlled ExperimentsMendel controlled fertilization in the pea plants, allowing him to see how traits pass from one generation to another.Mendel allowed some flowers to self-fertilize.He also performed cross-fertilization by transferring pollen from one pea flower to another.
9Mendel’s Unique Methods 4.1 Foundations of GeneticsMendel’s Unique MethodsUsed true-breeding plants for each trait—plants that always produce offspring with that trait when they self-pollinateRecorded the inheritance of traits for several generationsUsed a mathematical approach
10Mendel’s Experimental Results 4.1 Foundations of GeneticsMendel’s Experimental ResultsMendel concluded that two factors control each inherited trait.When organisms reproduce, each gamete— sperm or egg—contributes one factor for each trait.
114.1 Foundations of Genetics Dominant FactorsA genetic factor that blocks another genetic factor is called dominant.A dominant trait is observed when offspring have one or two dominant factors.
124.1 Foundations of Genetics Recessive FactorsA genetic factor that is hidden by the presence of a dominant factor is recessive.A recessive trait can be observed only when two recessive genetic factors are present in offspring.
13Mendel’s Laws of Heredity 4.1 Foundations of GeneticsMendel’s Laws of HeredityLaw of segregation: the two factors for each trait segregate—separate from each other—during meiosis when gametes formLaw of independent assortment: the factors for one trait separate independently of how factors for other traits separate
14Modern Definitions of Mendel’s Ideas 4.1 Foundations of GeneticsModern Definitions of Mendel’s IdeasMendel did not know about DNA or how cells reproduce, but his ideas about inheritance are still true today.
154.1 Foundations of Genetics Genes and AllelesA gene is a section of DNA that has information about a trait in an organism.Each form of a gene with different information is called an allele.
16Genes and Alleles (cont.) 4.1 Foundations of GeneticsGenes and Alleles (cont.)
17Phenotype and Genotype 4.1 Foundations of GeneticsPhenotype and GenotypeThe observable traits and all characteristics of an organism make up the organism’s phenotype.The alleles that make up an organism is the organism’s genotype.The alleles of a particular gene is that gene’s genotype.
18Homozygous and Heterozygous Genotypes 4.1 Foundations of GeneticsHomozygous and Heterozygous GenotypesBecause eukaryotes have pairs of chromosomes, a genotype for a gene has two alleles.If the two alleles have the same information, the genotype is homozygous.If the two alleles have different information, the genotype is heterozygous.
19Homozygous and Heterozygous Genotypes (cont.) 4.1 Foundations of GeneticsHomozygous and Heterozygous Genotypes (cont.)
20Law of Segregation Explained 4.1 Foundations of GeneticsLaw of Segregation ExplainedThe movement of chromosomes during meiosis explains Mendel’s law of segregation.Each set of chromatids separates into different gametes during meiosis II.Each gamete receives only one allele.
21Law of Segregation Explained (cont.) 4.1 Foundations of GeneticsLaw of Segregation Explained (cont.)
22Law of Independent Assortment Explained 4.1 Foundations of GeneticsLaw of Independent Assortment ExplainedThe daughter cells produced by meiosis receive only one chromosome from each pair of homologous chromosomes.A daughter cell might receive the A or a chromosome from pair 1 and the B or b chromosome from pair 2.This results in four possible allele combinations for two homologous pairs of chromosomes.
23Law of Independent Assortment Explained (cont.) 4.1 Foundations of GeneticsLaw of Independent Assortment Explained (cont.)
24Importance of Mendel’s Genetic Studies 4.1 Foundations of GeneticsImportance of Mendel’s Genetic StudiesIn the 1860s, no one knew about chromosomes or meiosis so it was hard to understand Mendel’s discoveries.All the research of modern genetics is based on Mendel’s conclusions from his work with pea plants.
25What is the passing of traits from parents to offspring called? 4.1 Foundations of GeneticsWhat is the passing of traits from parents to offspring called?A inheritanceB geneticsC heredityD alleleLesson 1 Review
26What are the alleles that make up an organism called? A genes 4.1 Foundations of GeneticsWhat are the alleles that make up an organism called?A genesB genotypeC phenotypeD factorsLesson 1 Review
274.1 Foundations of Genetics If two alleles for a gene have the same information, what kind of genotype does that gene have?A homologousB recessiveC heterozygousD homozygousLesson 1 Review
304.2 Understanding Inheritance Modeling InheritanceTwo tools can be used to identify and predict traits among genetically related individuals.Punnett squarepedigreeHeredity
314.2 Understanding Inheritance Punnett SquaresA Punnett square is a model used to predict possible genotypes and phenotypes of offspring.If the genotypes of the parents are known, the genotypes and phenotypes of the offspring can be predicted.
324.2 Understanding Inheritance One-Trait ModelThe Punnett square shows the possible offspring of a cross between two true-breeding pea plants—one with yellow seeds and one with green.
33One-Trait Model (cont.) 4.2 Understanding InheritanceOne-Trait Model (cont.)The only possible genotype for hybrid offspring is heterozygous—Yy.The phenotype will be yellow seeds because Y is dominant to y.
34One-Trait Model (cont.) 4.2 Understanding InheritanceOne-Trait Model (cont.)
354.2 Understanding Inheritance Two-Trait ModelThe possible offspring of two heterozygous genotypes—Yy and Yy—would have three different genotypes and two phenotypes.
364.2 Understanding Inheritance PedigreesAll the genetically related members of a family are part of a family tree.A pedigree shows genetic traits that were inherited by members of a family tree.Pedigrees are important tools for tracking complex pattern of inheritance and genetic disorders in families.
374.2 Understanding Inheritance Pedigrees (cont.)A pedigree chart that shows three generations of a family.
384.2 Understanding Inheritance Types of DominanceAlleles show incomplete dominance when they produce a phenotype that is a blend of the parents’ phenotypes.When both alleles can be observed in the phenotype, the interaction is called codominance.The human blood type AB is an example of codominance.
394.2 Understanding Inheritance Multiple AllelesSome genes have more than two alleles, or multiple 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.
41Sex-Linked Inheritance 4.2 Understanding InheritanceSex-Linked InheritanceChromosomes X and Y are the sex chromosomes—they contain the genes that determine gender or sex.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.
42Sex-Linked Inheritance (cont.) 4.2 Understanding InheritanceSex-Linked Inheritance (cont.)In this family, the grandmother’s genome included the color blindness allele.
43Polygenic Inheritance 4.2 Understanding InheritancePolygenic InheritancePolygenic inheritance is when multiple genes determine the phenotype of a trait.Many phenotypes are possible when possible when polygenic inheritance determines a trait.
444.2 Understanding Inheritance Maternal InheritanceHumans inherit mitochondrial genes only from their mothers.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?
45Human Genetic Disorders 4.2 Understanding InheritanceHuman Genetic DisordersIf a change occurs in a gene, the organism with the mutation may not be able to function as it should.An inherited mutation can result in a phenotype called a genetic disorder.
47Genes and the Environment 4.2 Understanding InheritanceGenes and the EnvironmentAn 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.
48Punnett squares model the ____ of offspring. A genotypes B phenotypes 4.2 Understanding InheritancePunnett squares model the ____ of offspring.A genotypesB phenotypesC genotypes and phenotypesD genesLesson 2 Review
49A incomplete dominance B codominance C multiple alleles 4.2 Understanding InheritanceWhat is the term for when alleles produce a phenotype that is a blend of the parents’ phenotypes?A incomplete dominanceB codominanceC multiple allelesD polygenic inheritanceLesson 2 Review
50How many Y chromosomes do females have? A 0 B 1 C 2 D 4 4.2 Understanding InheritanceHow many Y chromosomes do females have?A 0B 1C 2D 4Lesson 2 Review
52Chapter Resources Menu Chapter AssessmentCalifornia Standards PracticeConcepts in MotionImage BankScience OnlineClick on a hyperlink to view the corresponding feature.
53A polygenic inheritance B sex-linked inheritance What is the term for the idea that offspring are a blend of genetic material from both parents?A polygenic inheritanceB sex-linked inheritanceC maternal inheritanceD blending inheritanceChapter Assessment 1
54What type of alleles can only be observed in the phenotype when they are present as a homozygous genotype?A dominantB recessiveC inheritedD heterozygousChapter Assessment 2
55A law of independent assortment B law of heredity C law of segregation What is the term for the idea that inheritance of one trait is not influenced by inheritance of another trait?A law of independent assortmentB law of heredityC law of segregationD maternal inheritanceChapter Assessment 3
56A color of camellia flowers B human AB blood type C color blindness What is a good example of a trait that is determined by multiple alleles?A color of camellia flowersB human AB blood typeC color blindnessD human ABO blood groupChapter Assessment 4
57Why are male humans more likely to be color-blind than females? A maternal inheritanceB sex-linked inheritanceC polygenic inheritanceD incomplete dominanceChapter Assessment 5
58Which pea trait did Mendel not study? A seed color B pod color SCI 2.cWhich pea trait did Mendel not study?A seed colorB pod colorC flower positionD flower shapeCA Standards Practice 1
59SCI 2.dIf two plants with genotypes Mm are crossed, what percent of the offspring will have phenotype M?A 0%B 25%C 75%D 100%CA Standards Practice 2
60What is the term for when more than one gene determine a trait? SCI 2.c, 2.dWhat is the term for when more than one gene determine a trait?A incomplete dominanceB multiple allelesC polygenic inheritanceD sex-linked inheritanceCA Standards Practice 3
61Which does NOT describe Mendel’s experiments? SCI 2.dWhich does NOT describe Mendel’s experiments?A Mendel observed several generations of plants.B Mendel chose pea plants because they reproduce quickly.C Mendel counted small numbers of offspring.D Mendel used true-breeding plants.CA Standards Practice 4
62What type of genetic disorder is hemophilia? A dominant SCI 2.dWhat type of genetic disorder is hemophilia?A dominantB X-linked recessiveC codominantD recessiveCA Standards Practice 5