1. Introduction to Genetics Genetics = the scientific study of heredity

2. Check Your Understanding

3. Chromosomes –Tightly coiled DNA where your genes are carried. Genes –Sections of DNA that control your traits.

4. The Work of Gregor Mendel Austrian monk. Studied heredity. –Heredity: the passing on of characteristics from parents to offspring. –Characteristics that are inherited are called traits. First person to successfully predict how traits are transferred from generation to generation. Used garden peas in his experiments. The Father of Genetics

5. Why pea plants? –Reproduce sexually, which means that they produce male and female sex cells, called gametes. –In a process called fertilization, the male gamete unites with the female gamete. –The resulting fertilized cell, called a zygote, then develops into a seed.

6. He took pollen from a male plant and dusted it onto a female plant. –Parental generation (p) = the original pair of plants Mendel’s Experiment Female part Transfer pollen Pollen grains Male parts Cross-Pollination Offspring (f1) = first filial generation (f2) = second filial generation

7. His first experiments are called monohybrid crosses because they only deal with ONE single trait (height, color) mono means “one”

8. Each organism has two factors that control each of its traits. These factors are genes and that they are located on chromosomes. Genes exist in different forms called alleles. Conclusions Tall pea plant Short pea plant All tall pea plants 3 tall: 1 short P1P1 F1F1 F2F2

9. Alleles The different forms a gene can take (usually represented by letters). 2 Types of Alleles: 1.Dominant – allele that is always displayed; ex “A”. 2.Recessive – allele only displayed when paired w/ another recessive allele; ex “a”.

10. Mendel called the observed trait dominant and the trait that disappeared recessive. Mendel concluded that the allele for tall plants is dominant to the allele for short plants. TT T T tt t t Tall plant Short plant All tall plants F1F1

11. Genotype –Letter representation of the genetic make- up of an individual (AA, Aa, aa). Phenotype –An observable physical characteristic of an organism. (Tall/short, blue/brown, curled/straight).

12. F1F1 Tall plant TTT T t Tt tT t t t 3 Tall Short 1 Tall F2F2 Law of Segregation The way an organism looks and behaves is called its phenotype. Ex. Tall, yellow The allele combination an organism contains is known as its genotype. Ex. TT, Tt An organism’s genotype can’t always be determined by its phenotype. Tt xTt cross

13. An organism is homozygous for a trait if its two alleles for the trait are the same. (True-breeding) –Exp. TT or tt An organism is heterozygous for a trait if its two alleles for the trait differ from each other. (Hybrid) –Exp. Tt

14. Genetics & Probability Probability = the likelihood that a particular event will occur: –Ex. Coin flipping: 1/2 probability that coin will flip head/tail –If you flip the coin 3 times what's the probability of flipping 3 heads? 1/2 x 1/2 x 1/2 = 1/8 –*Past outcomes do not affect future ones!!* The principles of probability can be used to predict the outcomes of genetic crosses. –What is the probability of parents having two male offspring in a row? (1/2 x 1/2=1/4)

15. Punnett Squares Are used to predict and compare the genetic variations that will result from a cross. –The types of gametes go on the top and left sides of the square. –The possible gene combinations appear in the four boxes.

16. If you know the genotypes of the parents, you can use a Punnett square to predict the possible genotypes of their offspring. Tt T t T T t t

17. You try this one… AA A a

18. Check Your Understanding Question 1 The passing on of characteristics from parents to offspring is __________. D. allelic frequency C. pollination B. heredity A. genetics The answer is B. Genetics is the branch of biology that studies heredity.

19. Check Your Understanding Question 2 What are traits? Answer Traits are characteristics that are inherited. Height, hair color and eye color are examples of traits in humans.

20. Check Your Understanding Question 3 Gametes are __________. D. fertilized cells that develop into adult organisms C. both male and female sex cells B. female sex cells A. male sex cells The answer is C. Organisms that reproduce sexually produce male and female sex cells, called gametes.

21. Check Your Understanding Question 4 Which of the following genotypes represents a animal that is homozygous dominant for a trait? a. KK b. Kk c. kk

22. Check Your Understanding Question 5 Which of the following genotypes represents a plant that is homozygous recessive for height? c. tt b. Tt a. TT

23. Exceptions to Mendel Genetics: Part 2

24. Mendel’s Dihybrid Crosses Dihybrid Cross round yellow x wrinkled green Round yellow Wrinkled green All round yellow Round yellow Round greenWrinkled yellow Wrinkled green 9331 P1P1 F1F1 F2F2

25. Law of Independent Assortment He found they appeared in a definite ratio of phenotypes 9:3:3:1 9 round yellow: 3 round green: 3 wrinkled yellow: 1 wrinkled green. He concluded that the seed shape and seed color—are inherited independently of each other. This conclusion is known as the law of independent assortment.

26. Dihybrid Crosses A Punnett square for a dihybrid cross will need to be four boxes on each side for a total of 16 boxes. Gametes from RrYy parent RY Ry rYry Gametes from RrYy parent RY Ry rY ry RRYY RRYy RrYYRrYy RRYy RRyyRrYy Rryy RrYYRrYyrrYY rrYy RrYy Rryy rrYy rryy

27. Not all genes show simple patterns of dominant and recessive alleles. –Because the majority of traits are controlled by more than one gene/alleles. Exceptions to Mendel

28. Incomplete Dominance Cases in which one allele is not completely dominant over another. Neither allele is dominant. –Ex. Red flower x White flower = Pink flower

29. Codominance Cases in which both alleles are expressed. –Ex. White cow x Black cow = Speckled (white and black) cow.

30. Multiple Alleles When a gene has more than two alleles. Ex. Mice coat color is determined by one gene with four different alleles. Three different colors result from the combinations of these alleles.

31. Blood Types Multiple Alleles & Codominance In humans, there are four blood types (phenotypes): A, B, AB, and O Blood type is controlled by three alleles. A, B, O O is recessive, two O alleles must be present for the person to have type O blood A and B are codominant. If a person receives an A allele and a B allele, their blood type is type AB Crosses involving blood type often use an I to denote the alleles. See chart. 

32. Type O's are automatically OO and type AB is automatically AB. Type A and B can be homozygous or heterozygous.

34. Polygenic Traits Traits controlled by two or more genes. –Ex. At least three genes are involved in making the reddish-brown pigment in the eyes of fruit flies. Different combinations of alleles for these genes yield different eye colors.

35. Sex Linked Traits Some genes are located on the X chromosome. Females receive two alleles (XX) for these genes, but males only receive one (y). When doing a Punnett Square, use large X's and Y's to denote male and female, use superscript letters to designate the alleles. –Ex. hemophilia (bleeding) and color blindness are recessive sex-linked traits (XcXc or XcY). If the parent is a male, the genotype is automatically known. A colorblind male has to be b (recessive), since he only has one allele and colorblindness is recessive. A normal male must then be B (dominant). Females can be heterozygous for the colorblindness trait - they are called carriers. A female can be XBXB - normal, XBXb - carrier, or XbXb – colorblind.

36. The following shows a cross between a normal man and a woman who is a carrier.

37. What… MORE practice problems?

38. Check Your Understanding Question 1 In a certain cactus, prickly spines can be two pronged or one pronged. If a true breeding (homozygous) one-pronged cactus is crossed with a true breeding two- pronged cactus, the F1 generation has a mixture of spines, some are two-pronged, some are one- pronged. codominance Is this an example of codominance or incomplete dominance?

39. Check Your Understanding Question 2 ParentsBlood Types Mr. HartzelO Mrs. HartzelA Mr. SimonAB Mrs. SimonAB Mr. PeachO Mrs. PeachO BabyBlood type JenniferO RebeccaA HollyB A nurse at a hospital removed the wrist tags of three babies in the maternity ward. She needs to figure out which baby belongs to which parents, so she checks their blood types. Using the chart below, match the baby to its correct parents.