BIOL 1441 1st Edition Lecture 24 Outline of Last Lecture I Gregor Mendel II Theories of inheritance III Genes IV Mendel s laws of inheritance V Law of segregation VI Punnett square VII Test Crosses VIII Law of independent assortment Outline of Current Lecture I The Laws of Probability II The Multiplication Rule III Extending Mendelian genetics for a single gene IV The Spectrum of Dominance V Multiple Alleles VI Pleiotropy Current Lecture I The Laws of Probability a Probability ranges from 0 to 1 i Event certain to occur 1 100 ii Event certain not to occur is 0 0 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III IV b Event any collection of outcomes of an experiment c Independent events outcomes that do not effect each other i Ex Coin toss ii Coin toss outcome of one toss has no impact on the outcome of the next toss independent events iii Probability of tossing heads and tails iv 1 out of 2 choices d Probability i All possible outcome must equal 1 ii What is the chance of picking ace of spades out of a deck of cards 1 1 52 iii What is the chance of picking any other card except the ace of spades out of the deck 1 51 52 Multiplication Rule two independent events occurring a Chance that 2 coins flipped up in the air will both land on heads b Multiply the probability of one event one coin landing on heads times the probability of the second event the other coin landing on heads c x 25 chance that both coins will land on heads d The probability that two or more independent events will occur together is the product of their individual probabilities e Probability in an F1 monohybrid cross can be determined using the multiplication rule Pp x Pp f Like flipping a coin each gamete has a 1 2 chance of carrying the dominant allele and a 1 2 chance of carrying the recessive allele g Solving Complex Genetics Problems i Apply multiplication addition rules to predict the outcome of crosses involving multiple traits ii Dihybrid cross is equivalent to two independent monohybrid crosses occurring simultaneously iii To calculate the chances for various genotypes each trait is considered separately and then the individual probabilities are multiplied together Extending Mendelian Genetics for a Single Gene a Inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations i 1 When alleles are not completely dominant or recessive ii 2 When a gene has more than two alleles iii 3 When a gene produces multiple phenotypes The Spectrum of Dominance a Alleles can show varying degrees of dominance and recessiveness in relation to each other V VI b Mendel s traits Complete Dominance occurs when phenotypes of the heterozygote and dominant homozygote are identical PP or Pp purple flower c Codominance two dominant alleles affect the phenotype in separate distinguishable ways i Both are expressed distinctly flowers with splotches of two colors ii Blood types A B O iii Types A B codominant O recessive ii iv AA or Ai type A v BB or Bi type B vi ii Type O vii AB both A and B one does not affect the expression of the other d Incomplete dominance phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties i Creates a whole new phenotype blending of alleles e Relation Between Dominance Phenotype i A dominant allele does not subdue a recessive allele alleles don t interact ii Alleles different forms of a gene both are expressed 1 Variations in a gene s nucleotide sequence iii Recessive allele is expressed but the phenotype is masked or hidden by dominant phenotype f Frequency of Dominant Alleles i Dominant alleles are not necessarily more common in populations than recessive alleles ii Polydactyly born with extra fingers or toes dominant 1 1 baby out of 400 in US is born with extra fingers or toes 2 More common trait of five digits recessive iii Recessive allele is far more prevalent than the dominant allele in the population Multiple Alleles a Most genes exist in more than two allelic forms b ABO blood group 3 alleles for the enzyme I that attaches A or B carbohydrates to RBCs IA IB i Pleiotropy one gene many effects a Pleiotropy gene that controls several functions or has multiple phenotypic effects b Pleiotropic alleles responsible for the multiple symptoms of certain hereditary diseases i Cystic fibrosis sickle cell disease c Difficult to trace through families different symptoms appear as different disorders