1. Mendelian Genetics Preeyanan Sanpote,University of Phayao

3. Heredity & Genetics Heredity is …..the passing on of characteristics (traits) from parents to offspring Genetics is….. the study of heredity

4. Genetics is the study of genes. Genetics is the study of genes. Inheritance is how traits (characteristics) are passed on from generation to generation. Inheritance is how traits (characteristics) are passed on from generation to generation. Chromosomes are made up of genes, which are made up of DNA. Chromosomes are made up of genes, which are made up of DNA. Genetic material (genes,chromosomes, DNA) is found inside the nucleus of a cell. Genetic material (genes,chromosomes, DNA) is found inside the nucleus of a cell. Gregor Mendel is considered “The Father of Genetics" Gregor Mendel is considered “The Father of Genetics" History

5. Father of Genetics

7. Austrian monk Mendel…… Austrian monk used the scientific approach to identify two laws of inheritance discovered the basic principles of heredity by breeding garden peas (Pisum sativum) in carefully planned experiments

8. reproduced quickly reproduce sexually, reproduced quickly have two distinct, male and female, sex cells called gametes their traits are easy to isolate there are many varieties with distinct heritable characters showed obvious differences in the traits showed obvious differences in the traits Mating,cross-pollination can be controlled Mendel used peas.. (Advantages of pea plants for genetic study) Understood that there was something that carried traits from one generation to the next- “FACTOR”.

9.  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA   Mendel chose only characters that occurred in two distinct alternative forms  He also used varieties that were true- breeding (plants that produce offspring of the same variety when they self-pollinate) Particulate Inheritance

10. cross-fertilized true-breeding that were different in just one character “Law of Segregation” Monohybrid Crosses

11. Mendel mated two contrasting,true-breeding varieties, a process called hybridization The true-breeding parents are the P generation The hybrid offspring of the P generation are called the F 1 generation When F 1 individuals self-pollinate or cross- pollinate with other F 1 hybrids, the F 2 generation is produced Experiment

12. Stamens Carpel TECHNIQUE First filial generation offspring (F 1 ) Parental generation (P) RESULTS 32 145

13. EXPERIMENT P Generation (true-breeding parents) Purple flowers White flowers F 1 Generation (hybrids) All plants had purple flowers Self- or cross-pollination F 2 Generation 705 purple- flowered plants 224 white flowered plants

14. Mendel reasoned that only the purple flower factor was affecting flower color in the F 1 hybrids Mendel called the purple flower color a dominant trait and the white flower color a recessive trait The factor for white flowers was not diluted or destroyed because it reappeared in the F 2 generation Mendel discovered a ratio of about three to one, purple to white flowers, in the F 2 generation

15. Mendel observed the same pattern of inheritance in six other pea plant characters, each represented by two traits What Mendel called a “heritable factor” is what we now call a gene What Do the Peas Look Like?

16. Mendel studies seven characteristics in the garden pea

17. The results of Mendel’s F1 crosses for 7 characters in Pea plants

18. Mendel was the first biologist to use mathematics to explain his results quantitatively. Mendel predicted the concept of genes that genes occur in pairs that one gene of each pair is present in the gametes F 2 ratio 705 : 224 or 3.15 : 1

19. The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round : 1 wrinkled Mendel’s observed ratio was 2.96 : 1 The discrepancy is due to statistical error The larger the sample the more nearly the results approximate to the theoretical ratio Did the observed ratio match the theoretical ratio?

20. Mendel developed a hypothesis to explain the 3:1 inheritance pattern he observed in F 2 offspring During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. “Law of Segregation”

21. An organism with two identical alleles for a character is said to be homozygous for the gene controlling that character An organism that has two different alleles for a gene is said to be heterozygous for the gene controlling that character Unlike homozygotes, heterozygotes are not true-breeding Alleles

22. allele for purple flowers Locus for flower-color gene allele for white flowers Pair of homologous chromosomes Alleles

23. Gene – a unit of heredity; a section of DNA sequence encoding a single protein Genome – the entire set of genes in an organism the different forms of a characteristic. Alleles – the different forms of a characteristic. Locus – a fixed location on a strand of DNA where a gene or one of its alleles is located. Probability- the chances/percentages that something will occur. Punnett Squares- show how crosses are made. Dominant traits- traits that are expressed. Recessive traits- traits that are covered up. Genetic Terminology

24. Monohybrid cross- looking at only one trait Monohybrid cross- a genetic cross involving a single pair of genes (one trait);looking at only one trait Dihybrid cross – looking at only two traits Dihybrid cross – a genetic cross involving two pairs of genes (two traits);looking at only two traits P - Parental generation F 1 - First filial generation;offspring from a genetic cross. F 2 - Second filial generation of a genetic cross Genotype- the types of genes (alleles) present. Phenotype-the way organism looks and behaves/what it looks like. Homozygous- two of the same alleles. Homozygous- two of the same alleles. Heterozygous- two different alleles. Trait or Character-any characteristic that can be passed from parent to offspring

25. Trait: Seed Shape Alleles: R – Roundr – Wrinkled Cross: Round seeds x Wrinkled seeds RR rr Genotype :Rr Phenotype:Round Genotype : Rr Phenotype: Round Genotypic Ratio:all alike Genotypic Ratio: all alike Phenotypic Ratio: all alike Monohybrid Cross gametes r r R Rr Rr R  Homozygous dominant x Homozygous recessive  Offspring all Heterozygous (hybrids)called F 1 generation  Genotypic & Phenotypic ratio is all alike

26. gametes R r R RR RR Rr Rr r rr rr Genotype :Rr,rr Genotype : RR,Rr,rr Phenotype :Round & wrinkled Phenotype : Round & wrinkled Genotypic Ratio:1:2:1 Genotypic Ratio: 1:2:1 Phenotypic Ratio: 3:1 Trait: Seed Shape Alleles: R – Roundr – Wrinkled Cross: Round seeds x Round seeds Rr x Rr Rr x Rr  Heterozygous x Heterozygous  Offspring have 3 genotypes,called F 2 generation  Genotypic & Phenotypic ratio is not the same

27. P Generation F 1 Generation F 2 Generation phenotype: Genotype: Gametes: Sperm from F 1 ( Pp ) plant Purple flowers Pp Purple flowers White flowers PP pp P P P P p p p p Eggs from F 1 ( Pp ) plant PP pp Pp 1/21/2 1/21/2 3 : 1 phenotype: Genotype: Gametes:

28. Phenotype Purple White 3 1 1 1 2 Ratio 3:1 Ratio 1:2:1 Genotype PP (homozygous) Pp (heterozygous) pp (homozygous)

29. Applying the Law of Segregation

30. Test cross How can we tell the genotype of an individual with the dominant phenotype ? Such an individual could be either homozygous dominant or heterozygous The answer is to carry out a testcross : breeding the mystery individual with a homozygous recessive individual Test cross : Cross with a homozygous recessive individual.

31. When you have an individual with an unknown genotype, you do a test cross. If any offspring display the recessive phenotype, the mystery parent must be heterozygous Example, a plant with purple flowers can either be PP or Pp therefore, you cross the plant with a pp (white flowers, homozygous recessive) P-  pp

32. If you get all 100% purple flowers,then the unknown parent was PP P p P p P p P p p p P p p P p p If you get 50% white, 50% purple flowers, then the unknown parent was Pp

33. Dominant phenotype, unknown genotype: PP or Pp? Recessive phenotype, known genotype: pp Predictions If purple-flowered parent is PP If purple-flowered parent is Pp or Sperm Eggs or All offspring purple 1 / 2 offspring purple and 1 / 2 offspring white Pp pp p ppp P P P p TECHNIQUE RESULTS

34. cross-fertilized true-breeding that were different in just two characters Dihybrid Crosses “The Law of Independent Assortment”

35. Using a dihybrid cross, Mendel developed the law of independent assortment The law of independent assortment states that each pair of alleles segregates independently of each other pair of alleles during gamete formation Strictly speaking, this law applies only to genes on different, nonhomologous chromosomes or those far apart on the same chromosome Genes located near each other on the same chromosome tend to be inherited together

36. P Generation F 1 Generation Predictions Gametes EXPERIMENT RESULTS YYRR yyrr yr YR YyRr Hypothesis of dependent assortment Hypothesis of independent assortment Predicted offspring of F 2 generation Sperm or Eggs Phenotypic ratio 3:1 Phenotypic ratio 9:3:3:1 Phenotypic ratio approximately 9:3:3:1 315 108 101 32 1/21/2 1/21/2 1/21/2 1/21/2 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 1/41/4 9 / 16 3 / 16 1 / 16 YR yr 1/41/4 3/43/4 Yr yR YYRR YyRr yyrr YYRRYYRrYyRR YyRr YYRrYYrr YyRr Yyrr YyRR YyRr yyRR yyRr YyRr YyrryyRr yyrr

37. RYRyrYry RYRy rY ry Dihybrid Cross

38. RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow : 9 Round/green : 3 wrinkled/Yellow : 3 wrinkled/green : 1 9:3:3:1 phenotypic ratio RYRyrYryRY Ry rY ry Dihybrid Cross

39. Dihybrid test cross?? If you had a tall, purple plant,how would you know what genotype it is?  tt pp ?? 1. TTPP 2. TTPp 3. TtPP 4. TtPp

40. The laws of probability govern Mendelian inheritance Mendel’s laws of segregation and independent assortment reflect the rules of probability When tossing a coin, the outcome of one toss has no impact on the outcome of the next toss In the same way, the alleles of one gene segregate into gametes independently of another gene’s alleles

41. Segregation of alleles into eggs Segregation of alleles into sperm Sperm Eggs 1/21/2 1/21/2 1/21/2 1/21/2 1/41/4 1/41/4 1/41/4 1/41/4 Rr R R R R R R r r r r r  r

42. Inheritance patterns are often more complex than predicted by simple Mendelian genetics The relationship between genotype and phenotype is rarely as simple as in the pea plant characters Mendel studied Many heritable characters are not determined by only one gene with two alleles However, the basic principles of segregation and independent assortment apply even to more complex patterns of inheritance

43. Extending Mendelian Genetics for a Single Gene Inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations : – When alleles are not completely dominant – When a gene has more than two alleles – When a gene produces multiple phenotypes

44. Incomplete Dominance F1 hybrids in between phenotypes F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Example :snapdragons (flower) Example : snapdragons (flower) red (RR) x white (rr) RR = red flower rr = white flower R R rr

45. P Generation F 1 Generation 1/21/2 1/21/2 Red White Gametes Pink Gametes CWCWCWCW CRCRCRCR CRCR CWCW CRCWCRCW CRCR CWCW Incomplete Dominance

46. P Generation F 1 Generation F 2 Generation 1/21/2 1/21/2 1/21/2 1/21/2 1/21/2 1/21/2 Red White Gametes Pink Gametes Sperm Eggs CWCWCWCW CRCRCRCR CRCR CWCW CRCWCRCW CRCR CWCW CWCW CRCR CRCR CWCW CRCRCRCR CRCWCRCW CRCWCRCW CWCWCWCW

47. Summary of Mendel’s laws LAW LAW PARENT CROSS PARENT CROSS OFFSPRING OFFSPRING DOMINANCE TT x tt tall x short 100 % Tt tall 100 % Tt tall Tt x Tt tall x tall 75% or (3/4) tall 25% or (1/4) short 75% or (3/4) tall 25% or (1/4) short INDEPENDENT ASSORTMENT RrGg x RrGg round & green x round & green x round & green 9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow pods

48. Questions What did Mendel cross? What are traits? What are gametes? What is fertilization? What is heredity? What is genetics? What Did Mendel Find? What Did Mendel Find?

49. The two alleles for a trait must separate when gametes are formed A parent randomly passes only one allele for each trait to each offspring The genes for different traits are inherited independently of each other. Law of Independent Assortment Law of Segregation

50. How many alleles are there for each trait? What is an allele? How many alleles does a parent pass on to each offspring for each trait Questions..???

51. Dominantly Inherited Disorders Achondroplasia, a form of dwarfism with an incidence of one case among every 10,000 people. Heterozygous individuals have the dwarf phenotype. Huntington’s disease, a degenerative disease of the nervous system, is caused by a lethal dominant allele that has no obvious phenotypic effect until the individual is about 35 to 45 years old.

52. Key Male Female Affected male Affected female 1st generation 2nd generation 3rd generation Is a widow’s peak a dominant or recessive trait? Widow’s peak No widow’s peak WW or Ww Ww ww Ww ww

53. 1st generation 2nd generation 3rd generation Is an attached earlobe a dominant or recessive? Attached earlobe Free earlobe FF or Ff Ff ff FF or Ff ff

54. Widow’s peak No widow’s peak Attached earlobe

55. Parents Normal Aa Sperm Eggs Normal Aa AA Normal Aa Normal (carrier) Aa Normal (carrier) aa Albino A A a a Albinism

56. Parents Dwarf Dd Sperm Eggs Dd Dwarf dd Normal Dd Dwarf dd Normal D d d d Normal dd Dwarfism

57. Chromosomes carry hereditary (genes) Chromosomes (and genes) occur in pairs New combinations of genes occur in sexual reproduction Monohybrid vs. Dihybrid crosses Mendel’s Principles: Dominance: one allele masks another Segregation: genes become separated in gamete formation Independent Assortment: Members of one gene pair segregate independently from other gene pairs during gamete formation Summary of Genetics

58. Preeyanan Sanpote School of Science University of Phayao