Presentation on theme: "Mendelian Genetics The principles of probability can be used to predict the outcome of genetic crosses Probability - The likelihood that a particular event."— Presentation transcript:
1Mendelian GeneticsThe principles of probability can be used to predict the outcome of genetic crossesProbability - The likelihood that a particular event will occur is called probability.When a baby is born, the probability that it is a girl is 1:2 or 50%.
2Probability and Genetics Probability and Product Rule:How do you calculate the probability of more than one event occurring?Product Rule = Multiply the probability of each independent event together
3Probability and Genetics Example: What is the chance that a couple (both heterozygous for tongue rolling) will produce a baby girl who can roll her tongue?
4Probability and Genetics Begin by determining the probability of each event happening independently:What is the probability of producing a baby girl? ____________50% or 1/2
5Probability and Genetics What is the chance that a couple (both heterozygous for tongue rolling) will produce a child who can roll its tongue?Set up a Punnett Square!________________R r75% or 3/4R rRR RrRr rr
6Probability and Genetics The original question: What is the chance that a couple (both heterozygous for tongue rolling) will produce a baby girl who can roll her tongue? ________________What is the chance that this couple will produce a baby girl who cannot roll her tongue? ________________½ x ¾ = 3/8½ x ¼ = 1/8
7Gregor MendelMendel began his genetic research by crossing true-breeding pea plants, the P(arent) generation.The result of this cross is the F1 generation, which are hybrids.He next crossed the F1 generation to produce the F2 generation.
8Mendel’s Genetic Crosses P generationF1 generationF2 generation
9Mendel’s Research on 1 Trait What is the phenotype ratio of F2 generation?What is the genotype ratio of F2 generation?3 violet flowers:1 white flower1 BB: 2Bb: 1bb
10Mendel’s Law of Segregation Mendel recognized that each pea plant had two alleles for a trait.He hypothesized that one allele came from each of the two parent plants.Mendel’s law of segregation states: Allele pairs separate during gamete (sex cell) formation, and randomly unite at fertilization.
11Half the number of chromosomes as the parent cell Production of GametesHalf the number of chromosomes as the parent cell
12The Two-Factor CrossMendel next tested whether the segregation of alleles for one trait (example seed shape: round or wrinkled)affects the segregation of a second trait(example seed color: yellow or green)
13The Two-Factor CrossOne plant was true breeding for both yellow AND round seeds = P generationThis plant’s genotype was YYRRThe only alleles that could be produced by this plant were…Pass out whiteboards!
14The Two-Factor CrossThe second plant was true breeding for both wrinkled AND green seeds = P generationThis plant’s genotype was yyrrThe only alleles that could be produced by this plant were…yr
15The Two Factor Cross The only possible result of this cross is … YR YRRrYy = F1 generationWhat is the phenotype of the offspring?Round and yellow seeds.YyRrYyRryrYyRrYyRr
16The Two-Factor CrossMendel next crossed the offspring of the F1 generation. He crossed YyRr with YyRr. Each plant is called a dihybrid.Which alleles are created from YyRr?Work this out on your whiteboard!YRyRYryr
17The Two Factor Cross YR yR Yr yr YR yR Yr yr r yr Draw a 16 box Punnett Square to show the cross between YyRr and YyRrBegin by showingthe possible alleles.Then fill in theboxes!YRyRYryrr yr
19The Two Factor CrossWhat is the phenotype ratio for a two factor cross between dihybrids? Write on whiteboard!___________dominant for both traits – yellow and round seeds___________dominant for one trait and recessive for the second – yellow and wrinkled seeds93
20The Two Factor Cross3___________recessive for one trait and dominant for the second – green and round___________recessive for both traits – green and wrinkled1Phenotype ratio – 9:3:3:1
22Mendel’s 4th Conclusion Principle of Independent Assortment - genes for different traits can segregate INDEPENDENTLY during the formation of gametes.For example: A person can have blonde hair and blue eyes or brown hair and blue eyes. Hair color and eye color are inherited independently of each other.