1. Gregor Mendel Gregor Mendel: –Austrian monk lived from 1822-1884 –Mendel developed principles of heredity without any knowledge of genes or chromosomes –His principles were established through experiments with pea plants

2. Why was Mendel successful with the pea? Used pure breeding, 7 contrasting traits Studied characteristics one at a time for many generations Used mathematics in analyzing his results Obtained large numbers of offspring Chose pea plants which normally self-fertilize Inexpensive Used scientific method Easy to pollinate (transfer of male pollen to egg)

3. Mendel’s 7 contrasting traits

4. Genetics Terms Define genes: factors that control organism’s traits. the part of chromosome that contains the genetic code. Every organism requires a set of coded instructions for specifying its traits For offspring to resemble their parents, their must be a reliable way to transfer hereditary information from one generation to the next

5. Genetics Terms homozygous (pure): the alleles on homologous chromosomes are the same heterozygous: (hybrid): the alleles on homologous chromosomes are different parental generation (P): the two original organisms being crossed - usually pure first filial generation (F1) : the first generation of offspring from the parents second filial generation (F2) : generation of offspring arising from the first filial generation

6. Genetics Terms Genotype: the genetic makeup of an organism –Homozygous Dominant: TT –Homozygous Recessive: tt –Heterozygous: Tt Phenotype: the appearance of an organism –Describes what it looks like TT - Tall tt - short Tt - Tall

7. Punnett Squares a model used to predict the results of a genetic cross BB X bb b b B B BB B B b b b b

8. Three Laws by Mendel 1. Law of Dominance: a pattern of heredity in which one allele of a gene may express itself by masking the presence of the other allele Dominant Trait: the trait or allele that is expressed (capital letter) R Recessive Trait: the trait or allele that is present but that is not expressed (lowercase letter) r

9. Three Laws by Mendel 1. Law of Dominance: Example: red flower (RR) X white flower (rr)  red flower (Rr) X X 

10. Example of Dominance R = red r = white RR x rr R r Rr Results: Phenotype: Genotype: Problem: Cross homozygous dominant with homozygous recessive 100% red 100% heterozygous

11. 2. Law of Segregation Mendel’s second law –When gametes are formed during meiosis: There is a random segregation of homologous chromosomes Random segregation of sister chromatids & alleles The result: new gene combinations are likely to be produced Segregation means separation and can lead to genetic recombination.

12. Phenotype: ____% red, ____% white ___ red : ___ white Genotype: ___% homozygous dominant, ___% homozygous recessive, ___% heterozygous Example of Segregation R = red r = white Rr x Rr RrRr R r RRRr rr Problem: Cross two offspring from 1 st cross (2 heterozygous parents) 7525 13 50

13. 3. Law of Independent Assortment Mendel’s third Law –Scenario: Two different traits located on two different chromosomes They segregate randomly during meiosis May be inherited independently of each other The cross of two organisms heterozygous for a trait is known as a dihybrid cross

14. Law of Independent Assortment

15. Dihybrid Cross Problem: Cross homozygous tall and homozygous wrinkled seeds with homozygous short and homozygous smooth seeds T = tall t = short Q = wrinkled q = smooth What are the genotypes for these plants? TTQQ x ttqq

16. TtQq Phenotype: 100% Tall & Wrinkled TQ tq

17. Dihybrid Cross What is the phenotype from this cross? –100% Tall and Wrinkled What is the genotype from this cross? –We don’t worry about genotype for dihybrid crosses

18. Complete the following Dihybrid cross Step 1 - set up gamettes(sex cells) (1 3, 1 4, 2 3, 2 4) TtQq x TtQq

19. Complete the following Dihybrid cross TtQq x TtQq T-Tall t-short Q-Wrinkled q-smooth TTQQ TTQq TtQQ TtQq TtqqttQqttqq ttQq Ttqq TtQq TtQQTTQq TTqq TtQq ttQQ TtQq TQtQTq tq TQ Tq tQ tq

20. What are the phenotypes for the above cross??? - Tall & Wrinkled - Tall & smooth - Short & wrinkled - Short & smooth 9 3 3 1

21. Incomplete Inheritance Two examples of Incomplete Inheritance: –Incomplete Dominance & Codominance Incomplete Dominance: –A case where one allele is partially dominant over the other –Examples of Incomplete Dominance: red snapdragons X white snapdragons  pink snapdragons cross between black and white Andulusian fowl gives blue (gray) fowl

22. Example of Incomplete Dominance Pink Snapdragons X 

23. Results: Phenotype: ___% red, ___% pink, ___% white Genotype: ___% homozygous dominant ___% heterozygous ___% homozygous recessive Example of Incomplete Dominance R = red r = white Rr x Rr RrRr RrRr RR Rr rr Problem: Cross offspring from 1 st cross (2 heterozygous parents) 5025 50 25 Ratio ___ : ___ : ___ 121 121

24. Intermediate Inheritance Codominance: a case in which neither allele is dominant over the other –Alleles have equal power Examples: –Cross between red and white short horned cattle gives roan cattle –Checkered black & white chicken –Sickle-cell Anemia - a blood disease where RBCs are sickle shaped or half moon. Most common African. –Heterozygous - half normal half sickle shape

25. Roan Cattle Red Cattle X White Cattle  Roan Cattle

26. Results: Phenotype: ___% red, ___% red & white, ___% white Genotype: ___% homozygous dominant ___% heterozygous ___% homozygous recessive Example of Codominance R = red r = white Rr x Rr RrRr RrRr RR Rr rr Problem: Cross offspring from 1 st cross (2 heterozygous parents) 5025 50 25 Ratio ___ : ___ : ___ 121 121

27. Problem 1 Homozygous dominant Phenotype of tt ------------------------- Genotype of tt--------------------------- Phenotype of TT ----------------------- Genotype of TT------------------------- Phenotype of pure dominant-------- Genotype of pure dominant--------- Phenotype of pure recessive-------- Genotype of pure recessive--------- Short Homozygous recessive Tall Tall TT Short tt

28. __ __ x __ __ XY XXXX XXXY XX XY Results: Phenotype: 50% male, 50% female Phenotype ratio: 2 male : 2 female Problem 2: A married couple want to know their chances of having girl XYXX

29. Phenotype: ___% red, white ___% Phenotypic Ratio: __ : ___ Genotype: ___% heterozygous ___% homozygous dominant ____ % homozygous recessive R = red r = white __ __ x __ __ RrRr R r RRRr rr Problem 3: Cross two heterozygous parents RrrR 75 25 50 25 3 red 1 white

30. Results: Phenotype: ___% red, white ___% Phenotype Ratio: __ : _ _ __ Genotype: ___% heterozygous ___% homozygous dominant ___ % homozygous recessive R = red r = white __ __ x __ __R R r RR Rr Problem 4: Pure dominant crossed with hybrid RRr R 100 50 0 0 4 red4 white

31. Phenotype: ___% red, white ___% Phenotypic Ratio: __ : ___ Genotype: ___% heterozygous ___% homozygous dominant ___ % homozygous recessive R = red r = white __ __ x __ __ r R r Rr rr Problem 5: The male’s genotype is homozygous recessive. The female is phenotypically dominant but does carry the recessive allele. rrrR 50 0 2 red2 white

32. Results: Phenotype: ___% red, ___ % red and white, white ___% Phenotypic Ratio: __ red : __ red and white : ___ white Genotype: ___% heterozygous ___% homozygous dominant ___ % homozygous recessive R = red r = white __ __ x __ __ RrRr R r RR Rr rr Cross two heterozygous parents RrrR 25 50 25 12 Problem 6: Law of Codominance 50 1

33. Results: Phenotype: ___% red, ___ % pink, white ___% Phenotype Ratio: __ red : __ pink : ___ white Genotype: ___% heterozygous ___% homozygous dominant ___ % homozygous recessive R = red r = white __ __ x __ __ RrRr R r RR Rr rr Cross two heterozygous parents RrrR 25 50 25 50 12 Problem 7: Law of Incomplete Dom 25 1

34. Test Cross: It will determine if a horse/dog in question is pure or carrying a recessive gene.

35. B = brown b = white __ __ x __ __ or __ __ x __ __ B b Bb Problem 8: A test cross uses an individual that is homozygous recessive. It will determine if the dog in question is pure or carrying a recessive gene. BBbb Bbbb b B b bb

36. Multiple alleles Traits that are controlled by more than 2 alleles Results in multiple phenotypes Examples: –Pigeons B A dominant over B B A and B are dominant over b –Blood groups in humans Four blood types A B AB & O

37. X-linked Inheritance Examples: Hemophilia, Color Blindness, Loss of Hearing & Muscular Dystrophy

38. X-linked Recessive Inheritance ___% NORMAL HEARING of TOTAL OFFSPRINGS, ___ % HEARING LOSS of TOTAL OFFSPRINGS ___% NORMAL HEARING OF FEMALES ___ % HEARING LOSS OF MALES XDXdXDXd XDXD XdYXdYXDYXDY XDXDXDXD Y XDXD XdXd XDXdXDXd XDYXDY XdYXdYXDXdXDXd XDYXDYXDXDXDXD 75 100 50 25

39. Polygenic Inheritance A pattern of a trait that is controlled by 2 or more genes. Phenotype express a range of variability. Examples: –Stem length, human height, eye color & skin color Stem length for a totally recessive plant is____ cm. aabbcc = 4 cmAABBcc = cm Aabbcc = cmAABBCc = cm AAbbcc = cmAABBCC = cm AABbcc = cm

40. Gene Expression Influence of External Environment: Examples: Temp., nutrition, light, chemicals –Color of rabbit in the summertime: brown –Color of rabbit in the winter: white –The temperature effects what color fur (or what proteins) are expressed –Temp also determines the sex of a gator –Light determines color of bacteria

41. Gene Expression Influence of Internal Environment: Examples: Hormonal influences –Horn size in mountain sheep –Male pattern baldness –Peacock feathers

42. Gene Expression Influence of Internal Environment: Examples: Hormonal influences –Horn size in mountain sheep –Male pattern baldness –Peacock feathers

43. Nature vs. Nurture In many cases it is not only the genes that we have that determine what we look like Scenario: If identical twins (same DNA) were separated at birth and lived in 2 different environments and then brought together 25 years later would they look the same? Why or why not?

44. Nature vs. Nurture Answer: The identical twins would have similar features (eye color, size of nose, etc.) but may look very different. What they did throughout their lives effects what they look like –For example: sun exposure, diet, hygiene, injuries, etc.