Heredity and Genetics

1. Heredity and Genetics

2. DNA structure- Chromosomes • Chromosomes = long pieces of DNA

3. Chromosomes have genetic information and are passed on every time a cell divides Dividing onion cells chromosomes chromosomes cell wall nucelus

4. Chromosomes come in pairs Cut out from picture and match each in pairs

5. How many chromosomes? • Humans = 23 chromosome pairs, or 46 total. We think we have about 20 to 25,000 protein coding genes. • Pea flower = 7 chromosome pairs (14 total) • Fruit fly = 4 chromosome pairs (8 total) arguably 5,000 genes. • Potato = 24 pairs (total 48) • Horse = 32 pairs (total 64)

6. fruit fly 13,600 ref • Budding yeast 6,275 ref • human ~21,000 ref • human mitochondria 13 • rice 46,022 -55,615 • dog ~25,000 • mouse ~23,000

7. Information flow in cells protein traits DNA

8. Chromosome structure- genes • Regions of chromosomes called genes determine which proteins can be made in the cell • Traits result from which proteins are made Human chromosome # 7 • Contains about 1,800 genes • Contains over 150 million nucleotides Link to view genes and DNA sequence

9. Genes • The order, or sequence, of nucleotides in a gene is a code that cells use to make specific proteins ATAACAGGCGACTTACGGC GCCGTAAGTCGCCTGTTAT

10. Trait – a characteristic of an organism • Example: “flower color” Gene – part of a chromosome that helps determine a specific trait • Example: “flower color gene” Allele – a form of a gene • Example: • One allele is the “blue” form of the gene • One allele is the “red” form of the gene

11. DNA (gene) protein traits

12. “Roundbuds”

13. Roundbuds In a type of wildflower, the round bud, red pigment is synthesized from a colorless molecule by enzyme Q. 1. Draw the enzyme pathway for the round bud. 2. Some round buds are white. Explain why these flowers are white.

14. Red Pigment molecule colorless (white) molecule Enzyme Q Nodes = Metabolites Edges = Enzyme Colorless molecule Red pigment molecule Enzyme Q

15. Cell of RED flower Cell of WHITE flower Cell with gene for non-functional enzyme Q Cell with gene for functional enzyme Q

16. Pigment Metabolic Network for the Imaginary Bioflower Blue Flower Red Flower Where is the variation in these flowers? Blue and Red Flowers (Color)

17. Bioflowers • A colorless starting molecule is converted by enzyme X to blue pigment. Next, enzyme Y converts the blue pigment to red pigment. • Diagram of the pathway. (include a key) • Give an explanation for a blue flower.

18. pathway Colorless (white) molecule Blue pigment molecule Red pigment molecule Enzyme X Enzyme Y Molecule cartoons

19. Draw the enzymes and molecules present in the cells of each type of bioflower below. Type 1 X Y nucleus

20. Draw the enzymes and molecules present in the cells of each type of bioflower below. Type 2 X Y nucleus

21. Draw the enzymes and molecules present in the cells of each type of bioflower below. Type 3 X Y nucleus

22. Same species - different phenotype

23. Chromosomes come in pairs • You get one copy of a chromosome from one parent and one copy of a chromosome from the other parent. • This pair of chromosomes is called a “homologous pair” because they have the same genes on them - flower color gene Flower chromosome 3 (from computer simulation) From Dad From Mom

24. Chromosomes come in pairs IMPORTANT: homologous pairs have the same genes, but they are NOT IDENTICAL • Alleles can be different flower color gene “Blue” allele of flower color gene “Red” allele of flower color gene From Dad From Mom

25. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (or blue, red) blue, blue Observed characteristic RED RED BLUE

26. Dominant and recessive alleles Only one red allele is needed for the flower to look red. • Scientists call this a DOMINANT allele Two blue alleles are needed for the flower to look blue. • Scientists call this a RECESSIVE allele

27. Symbols used for alleles • The traditional symbols used for alleles are big and small letters • The letter chosen usually refers to the dominant allele Example: R = Red allele r = Blue allele

28. The combination of alleles determines the observed characteristics RED allele BLUE allele RED allele BLUE allele BLUE allele RED allele Chromosome combination Allele combination red, red red, blue (or blue, red) blue, blue Observed characteristic RED RED BLUE

29. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination Allele combination RR Rr rr Observed characteristic RED RED BLUE

30. Phenotype – the observed (or measurable) trait of an organism that relates to one gene Genotype – the two alleles that an organism has for a trait Example: Trait = “flower color” Phenotype = “RED” or “BLUE” Genotype = “RR” or “Rr” or “rr”

31. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination Allele combination RR Rr rr Observed characteristic RED RED BLUE

32. The combination of alleles determines the observed characteristics R R R r r r Chromosome combination GENOTYPE RR Rr rr PHENOTYPE RED RED BLUE

33. Biomolecular model with diploids GENOTYPE for flower type 1: Yes or no, is any functional enzyme Y in the cell? PHENOTYPE of flower type 1: Allele of chromosome 2A= Y1 (functional enzyme) 2A Allele of chromosome 2B= Y1 (functional enzyme) Y1 Y1 1A 2B 1B nucleus

34. Gregor Mendel • Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas • used experimental method • usedquantitative analysis • collected data & counted them • excellent example of scientific method

35. Mendel’s work • Bred pea plants • cross-pollinated true breeding parents (P) • raised seed & then observed traits (F1) • filial • allowed offspring to cross-pollinate & observed next generation (F2)

36. PP pp x Making crosses- an example • using representative letters • flower color alleles  P or p • true-breeding purple-flower peas  PP • true-breeding white-flower peas  pp Pp

37. On your sheet If a one chromosomed organism of Genotype Pp went through meiosis, and mated with another Pp organism that went through meiosis, what would the percent genotype of each offspring be?

38. self-pollinate Mendel’s work true-breeding purple-flower peas true-breeding white-flower peas X P PP pp phenotype 100% purple-flower peas 100% purple-flower peas F1 generation (hybrids) 100% 100% Pp Pp Pp Pp 75% purple-flower peas 75% purple-flower peas 25% white-flower peas 25% white-flower peas 3:1 3:1 F2 generation ? ? ? ?

39. PP 25% male / sperm P p Pp 50% 75% P Pp female / eggs pp p 25% 25% Punnett squares Pp x Pp % genotype % phenotype PP Pp Pp pp 1:2:1 3:1

40. Genotypes • Homozygous = same alleles = PP, pp • Heterozygous = different alleles = Pp homozygousdominant homozygousrecessive

41. purple PP homozygous dominant purple Pp heterozygous Phenotype vs. genotype • 2 organisms can have the same phenotype but have different genotypes

42. Punnett square practice Calculate the predicted genotypic and phenotypic ratios Calculate the probability of each genotype and phenotype • Hh X HH – H(hairy) is dominant over h(not hairy) • Gg X gg – G(green sepals) is dominant over g(yellow sepals)

43. Punnett Square F f Genotypic ratio: Phenotypic ratio: 1 Ff : 1 ff (2 Ff : 2 ff is OK) f f Ff ff 1 fat : 1 skinny (2 fat : 2 skinny is OK) Ff ff

44. What is the relationship between genotype and phenotype? • Give an example of a heterozygous genotype for height (T = tall; t = short): • Give an example of a homozygous genotype for height (T = tall; t = short): • What is the phenotype of a plant heterozygous for the height gene?

45. Dihybrid cross • Used to predict the combinations of 2 traits • For example: • Two double-heterozygous striped, with tail cats are crossed. • How many offspring will be striped and have a tail, how many will be striped with no tail, how many will be plain with a tail…

46. Practice • Construct a Punnett Square for each of the following crosses. • Write the Genotypic and Phenotypic Ratio below the Punnett Squares. • SsTt X SsTt • SSTt X SsTt • SSTT X SsTt S = striped s = plain T = tail t = no tail

47. SsTt X SsTt S = striped s = plain T = tail t = no tail

48. SsTt X SsTt S = striped s = plain T = tail t = no tail

49. SsTt X SsTt S = striped s = plain T = tail t = no tail

50. SsTt X SsTt S = striped s = plain T = tail t = no tail