* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download You Light Up My Life
Inbreeding avoidance wikipedia , lookup
Genome evolution wikipedia , lookup
Ridge (biology) wikipedia , lookup
Minimal genome wikipedia , lookup
Genome (book) wikipedia , lookup
Human genetic variation wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Point mutation wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Transgenerational epigenetic inheritance wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Nutriepigenomics wikipedia , lookup
X-inactivation wikipedia , lookup
Gene expression programming wikipedia , lookup
Biology and consumer behaviour wikipedia , lookup
Gene expression profiling wikipedia , lookup
Behavioural genetics wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Heritability of IQ wikipedia , lookup
Human leukocyte antigen wikipedia , lookup
Population genetics wikipedia , lookup
Designer baby wikipedia , lookup
Genomic imprinting wikipedia , lookup
Genetic drift wikipedia , lookup
Microevolution wikipedia , lookup
Hardy–Weinberg principle wikipedia , lookup
Observable Patterns of Inheritance Chapter 20 Earlobe Variations • If you have attached earlobes, you inherited two copies of the recessive allele • If you have detached earlobes, you may have either one or two copies of the dominant allele Gregor Mendel • Strong background in plant breeding and mathematics • Using pea plants, found indirect but observable evidence of how parents transmit genes to offspring Alleles • Different molecular forms of a gene • Arise by mutation • Dominant allele masks a recessive allele that is paired with it Allele Combinations • Homozygous – having two identical alleles at a locus – AA or aa • Heterozygous – having two different alleles at a locus – Aa Genetic Terms A pair of homologous chromosomes A gene locus A pair of alleles Three pairs of genes Genotype & Phenotype • Genotype refers to particular genes an individual carries • Phenotype refers to an individual’s observable traits • Cannot always determine genotype by observing phenotype Tracking Generations • Parental generation mates to produce P • First-generation offspring mate to produce F1 • Second-generation offspring F2 Mendel’s Theory of Segregation • An individual inherits a unit of information (allele) about a trait from each parent • During gamete formation, the alleles segregate from each other Segregation Parents: CC cc (meiosis) Gametes: C (meiosis) C c c AA parent produces only A gametes; aa parent produces only a gametes Probability The chance that each outcome of a given event will occur is proportional to the number of ways that event can be reached Punnett Square of a Monohybrid Cross Female gametes C Male gametes c C CC Cc c Cc cc Dominant phenotype can arise three ways, recessive only one Test Cross • Individual that shows dominant phenotype is crossed with individual with recessive phenotype • Examining offspring enables you to determine the genotype of the dominant individual Punnett Squares of Test Crosses c c C Cc Cc c cc cc Two phenotypes c c C Cc Cc C Cc Cc All dominant phenotype Independent Assortment • Mendel concluded that the two “units” for the first trait were to be assorted into gametes independently of the two “units” for the other trait • Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis Independent Assortment Metaphase I: A A a a B B b b OR A A a a b b B B Metaphase II: Gametes: A A a a A A a a B B b b b b B B B A B A 1/4 AB b a b a 1/4 ab b A b A 1/4 Ab B a B a 1/4 aB Dihybrid Cross Experimental cross between individuals that are homozygous for different versions of two traits Dihybrid Cross - F1 Results Parents: Gametes: F1 offspring: ccdd (smooth chin, no dimples) cd cd CCDD (chin fissure, dimples) CD CcDd CD Allele Combinations in F2 CcDd 1/4 CD 1/4 Cd 1/4 cD 1/4 cd 1/4 CD 1/16 1/16 1/16 1/16 CCDD CCDd CcDD CcDd 1/4 Cd 1/16 1/16 1/16 CCDd CCdd CcDd 1/16 Ccdd 1/4 cD 1/16 1/16 CcDD CcDd 1/16 ccDD 1/16 ccDd 1/4 cd 1/16 CcDd 1/16 ccDd 1/16 ccdd CcDd 1/16 Ccdd Pleiotropy • Alleles at a single locus may have effects on two or more traits • Classic example is the effects of the mutant allele at the beta-globin locus that gives rise to sickle-cell anemia Genetics of Sickle-Cell Anemia • Two alleles 1) HbA Encodes normal beta-hemoglobin chain 2) HbS Mutant allele encodes defective chain • HbS homozygotes produce only the defective hemoglobin; suffer from sickle-cell anemia Sickle-Cell Anemia • At low oxygen levels, cells with only HbS hemoglobin “sickle” and stick together • This impedes oxygen delivery and blood flow • Over time, it causes damage throughout the body Campodactyly: Unexpected Phenotypes • Effect of allele varies: – Bent fingers on both hands – Bent fingers on one hand – No effect • Many factors affect gene expression Polygenic Traits • Result from the combined expression of several genes • Skin color, eye color • Population may show continuous variation Continuous Variation • A more or less continuous range of small differences in a given trait among individuals • The greater the number of genes and environmental factors that affect a trait, the more continuous the variation in versions of that trait