1. Introduction to Genetics

2. Inheritance Why do you look like your parents? Why do some traits get passed down from grandparent to grandchild and skip one generation?

3. Mendel laid the groundwork for genetics. Genetics is the study of biological inheritance patterns and variation. Many in Mendel’s day thought traits were blended. Gregor Mendel showed that traits are inherited as discrete units.

4. Gregor Mendel Austrain Monk Born in 1822 Studied science and mathmatics at University of Vienna Taught at a monastery for 14 years Took care of the monastery garden

5. Gregor Mendel (1860s) He used the garden pea plants to study how traits were passed from one generation to another.

6. Why use pea plants? Controlled fertilization Distinctive traits (either-or) Rapid reproduction

7. Mendel’s Peas Parts of the plant – Pollen: carries the male sperm – Female part of the flower: produces eggs Fertilization: when egg and sperm join – Peas normally self-pollinate – Mendel controlled the pollination of his pea plants

8. Mendel’s Peas Mendel took true-breeding pea plants. He called this the P1 (parental generation) – True-breeding: if allowed to self-pollinate, they would always produce offspring identical to themselves Mendel cross-pollinated these plants and studied the results.

9. Mendel’s Peas Mendel Studied 7 traits each with two variations. Mendel took meticulous notes on the outcomes of each cross over three generations. – P generation: parent generation – F 1 generation: first offspring generation – F 2 generation: second offspring generation

10. Outcomes of F 1 Generation

11. Traits did not blend. They would have the same trait as one of the parents. Two conclusions – Biological inheritance is determined by factors that are passed from one generation to the next (genes) Variations of genes are called alleles – The Principle of Dominance: some alleles are dominant and others are recessive

13. Did the Recessive Allele Disappear? Mendel then allowed the F 1 Generation to self- pollinate. This produced the F 2 Generation The recessive traits returned in the F 2 Generation

14. Explanation of F 1 Cross Segregation of alleles: the separating of each allele Mendel hypothesized that the alleles segregated from each other during the formation of the gametes.

15. 1) The law of segregation States that each pair of genes segregates, or separates during meiosis Because of segregation, half of an organisms gametes contain one gene from a homologous pair and half of the gametes contain the other gene.

16. 2) The law of independent assortment States that gene pairs segregate into gametes randomly and independently of each other producing all possible combinations of chromosomes in the gametes. If the chromosome pairs did not separate randomly, offspring would have the same combinations of traits as one of the parents. In other words, without this law, you could not have your father’s eyes and your mom’s smile.

17. 3) The law of dominance States that if two alleles in a gene pair are different, then one allele can control the trait and the other one can be hidden. The dominant allele is expressed; the recessive allele is hidden.

18. Probability and Punnett Squares

19. Probability The likelihood of an event. Probability is equal to the fraction of something happening multiplied by how many times it occurs. – Example: ½ x ½ x ½ = 1/8 The principles of probability can be used to predict the outcomes of genetic crosses.

20. Probability Exercise As partners flip a coin 10 times each and record the number of heads and tails. Calculate the probability of getting a head or a tail based on your experiment. (# of events divided by total tries, Heads/10 & Tails/10) Figure the probability of the entire class by adding all of the heads and tails from all of the pairs.

21. Probability Exercise Questions What is probability? What is the actual probability of getting heads or tails? What does your data show as the probability for getting heads or tails? What does the class data show as the probability for getting heads or tails? Which is closer to the actual probability? Why? Can we predict events based on probability? Will our predictions always be exact? What would make them more exact?

22. Genes influence the development of traits. All of an organism’s genetic material is called the genome. A genotype refers to the makeup of a specific set of genes. A phenotype is the physical expression of a trait.

23. Homozygous vs. Heterozygous An allele is any alternative form of a gene occurring at a specific locus on a chromosome. – Each parent donates one allele for every gene. Homozygous describes an individual with two alleles that are the same at a specific locus. Heterozygous describes and individual with two alleles that are different at a specific locus.

24. Alleles can be represented using letters. A dominant allele is expressed as a phenotype when at least one allele is dominant. A recessive allele is expressed as a phenotype only when two copies are present. Dominant alleles are represented by uppercase letters; recessive alleles by lowercase letters.

25. Practice Question: Using P and p for the color of pea flowers, what is the genotype of a pea plant that is heterozygous for flower color. What is the phenotype?

26. Punnett Squares Diagrams used to predict and compare genetic variations that will result from a cross. Possible gametes from each parent are put at the top and side of the square. Combinations are represented in the intersecting squares.

27. A monohybrid cross involves one trait. Monohybrid crosses examine the inheritance of only one specific trait. – homozygous dominant-homozygous recessive: all heterozygous, all dominant

28. heterozygous-heterozygous— 1:2:1 homozygous dominant: heterozygous:homozygous recessive; 3:1 dominant:recessive

29. heterozygous-homozygous recessive—1:1 heterozygous:homozygous recessive; 1:1 dominant:recessive A testcross is a cross between an organism with an unknown genotype and an organism with the recessive phenotype.

30. Two-Factor Crosses

31. Independent Assortment Genes segregate independently of each other when there are two or more traits. – Occurs when gametes are formed. In a Two-Factor Cross (dihybrid) the alleles of the two factors segregate independently.

32. Figure 11-10 Independent Assortment in Peas

33. Steps in Creating this cross 1) Choose letters to represent the genes. Example: – In mice, the ability to run normally is a dominant trait. Mice with this trait are called running mice (R). The recessive trait causes mice to run in circles only. Mice with this trait are called waltzing mice (r). Hair color is also inherited in mice. Black hair (B) is dominant over brown hair (b).

34. Steps in Creating this cross 2) Write the genotypes of the parents. – Cross a heterozygous running, heterozygous black mouse with a heterozygous running, heterozygous black mouse. What is the phenotypic ratio of the offspring?

35. Steps in Creating this cross 3) Determine the possible gametes a parent can produce. F O I L

36. Steps in Creating this cross 4) Enter the possible gametes on the top and sides of the square.

37. Steps in Creating this cross 5) Complete the Punnett square by writing the alleles for the offspring in the appropriate boxes. RB rbrB Rb RB Rb rB rb

38. Steps in Creating this cross 5) Complete the Punnett square by writing the alleles for the offspring in the appropriate boxes. RB rbrB Rb RB Rb rB rb RRBB RRBb RRbb RrBB RrBb Rrbb rrBB rrBb rrbb

39. Steps in Creating this cross 6) Determine the phenotypes of the offspring RB rbrB Rb RB Rb rB rb RRBB RRBb RRbb RrBB RrBb Rrbb rrBB rrBb rrbb

40. Steps in Creating this cross 7) Using your results answer the problem. RB rbrB Rb RB Rb rB rb RRBB RRBb RRbb RrBB RrBb Rrbb rrBB rrBb rrbb

41. Cross a heterozygous running, heterozygous black mouse with a homozygous running, homozygous black mouse.

42. Cross a homozygous running, homozygous black mouse with a heterozygous running, brown mouse.

43. Cross a waltzing brown mouse with a waltzing brown mouse

44. Cross a homozygous running, heterozygous black mouse with a waltzing brown mouse.

45. Cross a heterozygous running, brown mouse with a heterozygous running, homozygous black mouse.