*Gregor Mendel. The Father of Genetics Born in Austria Entered a monastery at 21 University of Vienna

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1 Mendelian Genetics

2 Inheritance

3 *Gregor Mendel The Father of Genetics Born in Austria Entered a monastery at 21 University of Vienna Use mathematics to explain phenomena Variation in plants started experimenting with pea plants

4 *Gregor Mendel Peas were a good choice Many varieties of traits Ability to control mating pairs He began with truebreeding strains Experimented with hybridization

5 *Mendel s crosses Mendel cross bred 2 true-breeding varieties of a trait and examined their offspring Purple flowers x white flowers P = parental generation F 1 = First filial generation (P X P) F 2 = Second filial (F 1 X F 1 )

6 *Mendel crossed the F 1 to get the F 2 He repeated this many times Results: 705:224 Ratio of 3.15: 1

7 *Why this pattern? Why was the F 2 so significant? If you were Mendel, what information could you gather from this experience?

8 Mendel s 4 part hypothesis: 1. Alternative versions of genes account for variations in inherited chromosomes Today we know this as an allele Allele: alternative version of a gene that produces distinguishable traits Example: There are more that one color of eyes. Each color is produced by a different code so each color is considered its own allele. Blue, Brown, Green etc.

9 Mendel s 4 part hypothesis: 2. For each character, an organism inherits 2 alleles, one from each parent 2 copies of each chromosome, each with same gene loci These alleles can be the same or different

10 Mendel s 4 part hypothesis: 3. If two alleles at a locus differ, then the dominant allele determines the organism s appearance; the other, the recessive allele, has no noticeable affect on appearance Translation: If alleles are different, then one will be expressed - the dominant one Dominant trait: trait that will always be expressed Recessive trait: trait that can be hidden

11 Mendel s 4 part hypothesis: 4. The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes What known phenomenon has Mendel discovered? The Law of Segregation

12 Who is Gregor Mendel?

13 What did he do?

14

15 What else did you learn?

16 4 parts of his research Alternative versions of genes account for variations in inherited chromosomes For each character, an organism inherits 2 alleles, one from each parent If two alleles at a locus differ, then the dominant allele determines the organism s appearance; the other, the recessive allele, has no noticeable affect on appearance The two alleles for a heritable character separate (segregate) during gamete formation and end up in different gametes

17 Really important vocabulary Allele Dominant allele Recessive allele Law of segregation

18 Law of Segregation What is it?

19 How did Mendel find this out? He did crosses Data!

20 More really important vocabulary! Homozygous: Organism has identical alleles Heterozygous: Organism has different alleles Genotype = genetic makeup of an organism, represented by letters Phenotype = Visible or measurable traits that are based upon genotype

21 Using our vocab- modern notation Homozygous Heterozygous Genotype Phenotype

22 Ok, now what? The value of Mendel s discoveries Predictable patterns of inheritance Parent to offspring Law of segregation seen in single trait crosses

23 Punnett Squares! What are they good for? Easy way to predict genetic outcomes! Illustrate the Law of Segregation Shows all possible gametes

24 Punnett Square Set up Monohybrid cross - crossing one heterozygote with another

25 Notice anything? Count up genotypes and phenotypes Ratios can be predicted Genotypic ratio = 1:2:1 Phenotypic ratio = 3:1

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27 Lets do some practice Punnett squares! Count up genotype and phenotype ratios Can we compute probabilities? PP x pp Pp x Pp Yy x YY

28 Parents:

29 Parents:

30 Test Cross Can we determine the genotype of a parent when it is unknown? P_ X pp All purple offspring 50% purple, 50% white

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32 Mendel also discovered the Law of Independent Assortment How did he discover this law without modern knowledge of cell division or chromosomes? Results can be seen in his experimental crosses for 2 traits

33 Dihybridcrosses Two Factor Crosses- 2 traits Both parents are heterozygous for both traits Let s set up the parents! Y and R

34 Parents Y = yellow seed y = green seed R = round r = wrinkled What are the parent phenotypes?

35 Calculation time Phenotypes: Phenotype Ratio: Probability: Genotype ratio: Is there anything predictable about these crosses?

36 Parents:

37 What is independent assortment?

38 Look it s Independent Assortment! Gamete possibilities RY Ry ry Ry Each parent would have four possible gametes, creating 16 possible combinations for fertilization

39 *An important side note Mendel s laws of segregation and independent assortment only work for genes located on separate chromosomes What about genes on the same chromosome? They move by different rules More on this later

40 Partner practice

41 Practice Problems Pea pod shape: I = inflated, i = constricted Parents: Ii x Ii Find phenotype ratio Find genotype ratio What is the probability of getting a inflated pea pod in the offspring?

42 Practice Problems Flower position: A= axial, a = terminal Stem height: T= tall, t= short Parents: AaTt x AaTt Find phenotype ratio What is the probability of getting an axial flower and a short stem? What is the probability of getting a terminal flower and a tall stem?

43 Practice Problems Flower position: A= axial, a = terminal Stem height: T= tall, t= short Parents: Aatt x aatt Find phenotype ratio What is the probability of getting an axial flower and a tall stem? What is the probability of getting a terminal flower and a short stem?