Biology 22: Genetics and Molecular Biology

1. Biology 22: Genetics and Molecular Biology Spring Semester 2008

2. Enrollment • Biology 22 is currently full. • Please sign-in on the sheet to your left (next to your name) if you are in the class. • Please sign-in on the sheet to your right if you want to add the class; include lab section.

3. Enrollment • If you want to add, you must show up on the first lab day to see if a spot is available. • If a places are available, names will be chosen on Friday in lab. • All decisions to determine if places are available and the handing out of “add numbers” will be completed by this Friday.

4. Syllabus • Please read through carefully. • Brief discussion of key points • Summary of key points: • Bio 21 (or equivalent) & Chem 11 pre-requisites • English 1 advisory • Bio 22 covers genetics and molecular • No make-up exams or assignments

5. Ch 3 Basic Principles of Heredity

6. Mendelian Genetics & monohybrid crosses Mendel’s 1st Law Predicting Genetic Outcomes Punnett Squares Formulas for more complex problems Other genetic concepts Test Cross Incomplete dominance IN LAB ON FRIDAY Di-hybrid Crosses Chi-Square Test (you will apply this test to the data collected). Outline

7. Gregor Mendel 1822-1884

8. (Or the other way around!) MONOHYBRID CROSS Reciprocal cross homozygotes F1 filial heterozygotes F2 3:1 ratio

9. MONOHYBRID CROSS • The disappearance of trait in F1? • The re-appearance of trait in 25% of F2? But why did Mendel observe…

10. Mendel reasoned that: • 2 alleles exist • Alleles are either • Dominant • Recessive Round wrinkled

11. Thus Mendel proposed: 1. Each trait is governed by two factors – now called genes. 2. Genes are found in alternative forms called alleles. 3. Some alleles are dominant and mask alleles that are recessive.

12. Mendel’s 1st Law • Principle of Segregation • A diploid organism has 2 alleles for a characteristic. • The alleles separate and the gamete receives only one of these alleles. • Alleles separate in equal proportions.

13. Review concept: Segregation during meiosis Be able to identify Homologous chromosomes Alleles

14. PUNNETT SQUARE 1) a method to predict genotypic and phenotypic ratios (backcross example)

15. Round seeds versus wrinkled seeds Parentals: RR x rr F1 x F1: Rr x Rr R R r r R r R r ½ R ½ r r r ¼ RR ¼ Rr R R Rr Rr ½ R ½ r ¼ Rr ¼ rr Rr Rr

16. 2) Rules of probability to predict outcomes 1/6 x1/6 =1/36 1/6 + 1/6=2/6=1/3 either/or and Independent events ordered Mutually exclusive

17. Genetic applications • What is the P that two heterozygous parents have 3 children ALL with albinism? • What is the P that they have 3 children, 1 with albinism and 2 with normal pigmentation? • ANN or NAN or NNA 9/64 + 9/64 + 9/64 = 27/64 ¼ x ¼ x ¼ = 1/64

18. Binomial Rule • What is the P that they have 5 children 2 with albinism and three normal pigmentation? “unordered event” • P = n!/s!t! asbt • P = 5!/2!3! (1/4)2 (3/4)3 = 0.26

19. A “Test Cross” • What is a test cross? • Known recessive genotype X unknown genotype • What do we learn from a test cross?

20. Intermediate expression of traits. • Incomplete dominance

21. Know these terms • Gene • Allele • Dominant • Recessive • Locus • Genotype • Homozygote • Heterozygote • Phenotype • Incomplete Dominance • Character

22. End of lectureclick to practice some problems.

23. Practice Problems • Try your skills at the following problem. • First some rules & concepts are reviewed. • Problem • Powerpoint will be updated with answers and posted on ecompanion.

24. Note: When solving genetics problems • Convert parental phenotypes to genotypes • Use Punnett Square to determine genotypes of offspring • Convert offspring genotypes to phenotypes

25. Using Probability in Genetic Analysis 1. Probability (P) of an event (E) occurring: P(E) = Number of ways that event E can occur Total number of possible outcomes Eg. P(Rr) from cross Rr x Rr 2 ways to get Rr genotype 4 possible outcomes P(Rr) = 2/4 = 1/2

26. Using Probability in Genetic Analysis 2. Addition Rule of Probability – used in an “either/or” situation P(E1 or E2) = P(E1) + P(E2) Eg. P(Rr or RR) from cross Rr x Rr 2 ways to get Rr genotype 1 way to get RR genotype 4 possible outcomes P(Rr or RR) = 2/4 + 1/4 = 3/4

27. Using Probability in Genetic Analysis 3. Multiplication Rule of Probability – used in an “and” situation P(E1 and E2) = P(E1) X P(E2) Eg. P(wrinkled, yellow) from cross RrYy x RrYy P(rr and Y_) = 1/4 x 3/4 = 3/16

28. Using Probability in Genetic Analysis 4. Conditional Probability: Calculating the probability that each individual has a particular genotype

29. INTRODUCTION TO PROBLEM Phenylketonuria (PKU) is a genetic disorder that is characterized by an inability of the body to utilize the essential amino acid, phenylalanine.

30. PROBLEM Jack and Jill do not have PKU, however each has a sibling with the disease. What is the probability that Jack and Jill will have a child with PKU? What is the probability they will not have a child with PKU?

31. PROBLEM What is the probability they will not have a child with PKU?

32. Using Probability in Genetic Analysis 5. Ordered Events: use Multiplication Rule For Jack and Jill, what is the probability that the first child will have PKU, the second child will not have PKU and the third child will have PKU?

33. Using Probability in Genetic Analysis 6. Binomial Rule of Probability Out of 3 children born to Jack and Jill, what is the probability that 2 will have PKU?

34. The End