Asexual Reproduction

1. Asexual Reproduction • One parent • Offspring are identical to parent/ No genetic variation • Examples: Vegetative propagation, budding, cloning, mitosis (remember ?) • Why is this beneficial? • Fast • If it is not broke, don’t fix it!

2. Sexual Reproduction • Why sex? • Energetically expensive  • Health risks of childbearing  • Genetic diversity/Genetic Recombination  • Overall health of the species  • Meiosis makes the gametes • Spermatogenesis=4 identical sperm cells, puberty to death • Oogenesis=1 egg cell per month in humans, initial egg production before birth then freezing at Prophase I • Governed by two laws: Segregation and Independent Assortment

3. Rr parent Dominant allele for seed shape Recessive allele for seed shape Figure 13-7 Chromosomes replicate Meiosis I Alleles segregate Meiosis II Gametes Principle of segregation: Each gamete carries only one allele for seed shape, because the alleles have segregated during meiosis.

4. Figure 13-8 R y y Replicated chromosomes prior to meiosis R r r Y Y R R r r Alleles for seed shape r r R R Alleles for seed color Chromosomes can line up in two ways during meiosis I Y y Y y y y Y Y Meiosis I Meiosis I r r r r R R R R Y Y y Y y Y y y Meiosis II Meiosis II r r r r R R R R Gametes y y Y y Y Y Y y 1/4 RY 1/4 rY 1/4 Ry 1/4 ry Principle of independent assortment: The genes for seed shape and seed color assort independently, because they are located on different chromosomes.

5. Chromosome number and fertilization • Diploid (2n)=full set of chromosomes, is the result of fertilization with gametes • Homologs for each chromosome, 1 from mom, 1 from dad • In humans-22 autosome pairs, 1 sex-determing pair • Haploid (n)=1/2 set of chromosomes, is the result of meiosis • See examples and practice.

6. Increasing genetic variation even more: • During Metaphase I in meiosis, homologous chromosomes line up at the equator of the cell forming a tetrad. • This is when crossing over can occur.

7. Crossing Over • Homologous chromosomes exchange portions of DNA. • A gene’s distance from the centromere is related to the frequency of cross over. • As meiosis continues this increases the differences between gametes and possible offspring.

9. M&M Comparison • T Chart • Comparison Activity with Fuzzy Sticks. • Draw only the cells required. • Increase genetic diversity during Step by adding Crossing Over. ACTUALLY cut your “chromosomes” and reattach to model crossing over. • Fertilization must occur with another group.

10. Mitosis vs. Meiosis Activity(20 min.) Complete the activity on your own paper. Draw ONLY the cells requiredwith the appropriately sized and colored chromosome. When modeling Metaphase I demonstrate CROSSING OVER in one of the homologous pairs of your model. Fertilization must be completed with another group at the same point in the activity. Answer all questions.

11. Cell Cycle Lab Pt. II (online) • Go to Pearson Lab Bench and complete the Meiosis Tutorial with questions. • Data on your lab paper: Use the data from the Sordaria slide on the Analysis page to fill in Part II data for your lab sheet. • Take the lab quiz.

12. Figure 12-1-Table 12-1

13. Normal human karyotype Figure 12-6a

14. Karyotyping= picture of chromosomes for counting/sexing/diagnosing. Shows autosomal and sex chromosomes • Failure of chromosome separation during meiosis is called nondisjunction • Results in cells with an extra chromosome or missing a chromosome • When these cells are fertilized, this causes trisomies and monosomies • Kleinfelter’s-Trisomy 23 XXY • Turner’s-monosomy 23 XO • Jacob’s-XYY • Down’s-trisomy 21 • Patau’s syndrome=trisomy 13 • Crie du Chat=missing a portion a chromosome

15. Normal human karyotype Figure 12-6a

16. Figure 12-15 NONDISJUNCTION n + 1 n + 1 n – 1 2n = 4 n = 2 n – 1 3. Meiosis II occurs normally. 1. Meiosis I starts normally. Tetrads line up in middle of cell. 2. Then one set of homologs does not separate (= nondisjunction). 4. All gametes have an abnormal number of chromosomes—either one too many or one too few.

17. Figure 12-15-Table12-4

18. 1 16 1 12 1 36 1 20 1 60 1 100 1 180 1 1000 1 300 Figure 12-16

19. Genetics Review (heredity) • Notes • Sponge Bob: basic inheritance (complete dominance) • Incomplete, Codominance, Pollyallele • Sex-linked Traits • Dihybrids • At least two of each problem!

20. Laws of Genetics • Law of Segregation-Traits are separated from one another in the parents (we now know that this is due to meiosis) • Law of Independent Assortment-The inheritance of one trait doesn’t affect the inheritance of another (this is only true if traits are on different chromosomes, i.e, not “linked”)

21. Rr parent Dominant allele for seed shape Recessive allele for seed shape Figure 13-7 Chromosomes replicate Meiosis I Alleles segregate Meiosis II Gametes Principle of segregation: Each gamete carries only one allele for seed shape, because the alleles have segregated during meiosis.

22. Figure 13-8 R y y Replicated chromosomes prior to meiosis R r r Y Y R R r r Alleles for seed shape r r R R Alleles for seed color Chromosomes can line up in two ways during meiosis I Y y Y y y y Y Y Meiosis I Meiosis I r r r r R R R R Y Y y Y y Y y y Meiosis II Meiosis II r r r r R R R R Gametes y y Y y Y Y Y y 1/4 RY 1/4 rY 1/4 Ry 1/4 ry Principle of independent assortment: The genes for seed shape and seed color assort independently, because they are located on different chromosomes.

23. Mendel and Genetics • Mendel bred pea plants to determine the rules of heredity • Terms: • P=Parent generation • F1=First filial generation (offspring from P) • F2=Second filial generation (offspring from F1) • Allele=alternate form of a trait • Dominant=always expressed • Recessive=only expressed if dominant isn’t present • Homozygous=2 copies of the same allele(pure/true breeding,) • Heterozygous=2 different alleles (carrier, hybrid) • Genotype=Combination of genes (letters) • Phenotype=Expression of the combination of genes • Selfed/Self-fertizilation=crossed with same genotype • Testcross=cross with homozygous recessive to determine unknown phenotype.

24. What Mendel figured out • Rarely blending of inheritance (purple x white yields either purple or white, not lavendar) • Alternate versions of each gene exist (2 alleles for each gene) • Each individual inherits 1 allele from each parent • Predictable ratios occur when crossing individuals • + 2 laws of inheritance

25. Types of crosses • Monohybrids-tracing inheritance of 1 trait at a time • Complete Dominance = 1 loci, 2 phenotypes are possible • Practice Problems #1, 6, 12,

26. A cross between two homozygotes Homozygous mother Figure 13-4 Meiosis Female gametes Homozygous father Male gametes Meiosis Offspring genotypes: All Rr (heterozygous) Offspring phenotypes: All roundseeds A cross between two heterozygotes Heterozygous mother Female gametes Heterozygous father Male gametes Offspring genotypes: 1/4 RR :1/2 Rr : 1/4 rr Offspring phenotypes: 3/4 round:1/4 wrinkled

27. In pea plants, spherical seeds (S) are dominant to dented seeds (s). In a genetic cross of two plants that are heterozygous for the seed shape trait, what fraction of the offspring should have spherical seeds? • Write the genotypic and phenotypic ratios?

28. Test Cross – to determine an unknown genotype. • Deafness in dogs is a recessive trait. A breeder has a dog that can hear and wants to decide if they should breed the dog for money or not. Show a Punnett square to demonstrate how they would determine if the dog carried the deafness allele.

29. Phenylketonuria in humans is a recessive trait. Two parents are healthy and have no dietary restrictions however the mother knows her mother had PKU. Show the Punnett square of a cross between these two individuals. • What are the chances they will have a child with PKU? What are the chances they will have a child that is a carrier for PKU?

30. Types of crosses • Dihybrids-tracing inheritance of 2 traits together at a time. • Complete Dominance = 1 loci, 2 phenotypes are possible • Practice Problems # 2,10 and pg.284 #7

31.      Hypothesis of independent assortment: Alleles of different genes don’t stay together when gametes form. Female parent Figure 13-5a F1 PUNNET SQUARE Female gametes Male parent Male gametes F1 offspring all RrYy F2 female parent Alleles at R gene and Y gene go to gametes independently of each other F2 PUNNET SQUARE Female gametes F2 male parent Male gametes F2 offspring genotypes: 9/16 R–Y– : 3/16 R–yy : 3/16 rrY– : 1/16 rryy F2 offspring phenotypes: 9/16 : 3/16 : 3/16 : 1/16

32. Tall is dominant to short in pea plants. Green is dominant to white in pea plants. • A heterozygous tall, heterozygous green pea plant is crossed with a Short, heterozygous green pea plant. • What are the chances they will produce short, white pea plants?

33. Beyond what Mendel Knew Incomplete #3,14,7 (because of how it is worded) Codominance #5, 13, 7 (in real life)

34. Incomplete dominance in flower color Figure 13-17b Parental generation F1 generation Self-fertilization F2 generation White Purple Lavender

35. In some cats, the gene for tail length shows incomplete dominance. Cats with long tails or no tails are homozygous. Show the cross between a cat with a long tail and a cat with no tail. What is the phenotypic ratio of the F1? • White flowers and red flowers produce stripes in red and white. What type of dominance is shown?

36. Polyalleleic-one loci but many alleles. (complete and codominance) #4,8 • Blood Typing: There are three alleles that create human blood types. Chart…

37. Sex –linked traits(Complete Dominance) #9,11,15 • Ex. Eye color is an X-linked trait in fruit flies. Red is the dominant allele for this trait. Therefore white eyed females will only produce white eyed male offspring. • Hemophilia is an X-linked recessive trait. Show the punnet square between a normal male and a female who carries the trait for hemophilia. What are the chances they will have a child with hemophilia?

38. Dihybrid Cross A = Axial Flowers, a = terminal flowers R = Round Seed, r = wrinkled seed • P Generation: A plant that is heterozygous for both traits crossed with a plant that is heterozygous for flower location and homozygous dominant for seed shape. • Textbook #7, 12 • Use these for multiple traits at a time OR polygenic traits. Example: Eye Color AABBCC or aabbcc

39. But what is dominant, really? • Tay-Sachs-inability to metabolize certain lipids because of a malfunctioning enzyme • Only children with 2 copies of the allele have the disease-at the organismal level, this is recessive • However, heterozygotes, biochemically appear to be the result of incomplete dominance-lipid metabolism levels are intermediate between those who don’t have Tay-Sachs and those who • Molecularly, heterozygotes produce equal levels of functional and non-functional enzymes-appearing to be co-dominant

40. Other single-gene locus influences • Multiple alleles • Ex: Human Blood type • IA, IB, i • Pleiotropy • When a single gene affects many traits • Ex: sickle cell disease and its multiple symptoms

41. Sex-linked Traits • X-chromosome inheritance • b/c males have only 1 copy, they’re most likely affected by these, but females can still inherit these • Pass from mother to children • Y-chromosome inheritance • Only males affected • Pass from father to sons

42. Two or more genes • Epistasis • One gene alters the expression of another at a separate locus • Ex: in mice, B=black, b=brown, however, a second gene determines whether or not pigment will be deposited in the fur, so if organism is homozygous recessive for that gene, the mouse is albino • Polygenic Traits • Ex: human height, skin color, hair color • Spectrum of possible phenotypes that exist along a bell curve • Multiple genes and therefore lots of combinations of dominant and recessive alleles influence these traits

43. Figure 13-19 A phenotype distribution that forms a bell-shaped curve. Normal distribution—bell-shaped curve

44. Figure 13-20 Wheat kernel color is a quantitative trait. Hypothesis to explain inheritance of kernel color Parental generation aa bb cc (pure-line white) AA BB CC (pure-line red) F1 generation Aa Bb Cc (medium red) Self-fertilization F2 generation 20 15 15 6 6 1 1

45. Other Genetic Patterns • X-Inactivation-In females only, one X chromosome is inactivated (Barr Body) in each cell. • Different cells may inactivate a different X • ex: calico cats (Black, orange), lymph node patterns in women • Linkage-Recall that genes found on the same chromosome are “linked” • These don’t segregate via meiosis • The only way to get recombinations is via crossing over, therefore the further apart these are, the more chance of a crossover between them • % recombinants is proportional to the distance linked traits have between them-see AP Lab 3 Sordaria

46. Does Genotype determine Phenotype? • The short answer is “no!” • Environmental influences also affect gene expression, giving us a norm of reaction for a phenotype (range of possible phenotypes)

47. Pedigree Analysis • Pedigrees are family trees that use specific notations that geneticists use to predict the inheritance pattern of a trait

48. I Carrier male Carrier female Figure 13-21 Carriers (heterozygotes) are indicated with half-filled symbols Each row represents a generation II Affected male III Affected female IV

49. Figure 13-23 I Prince Albert Queen Victoria Female carrier of hemophilia allele II Affected male III IV

50. Commonly Inherited Disorders • Recessives • Tay-Sachs, Sickle Cell, Cystic Fibrosis, albinism • Dominants • Marfan syndrome, Huntington’s disease, Dwarfism • Sex-linked, X-chromosome • Color-blindness, several forms of muscular dystrophy, pattern baldness, hemophilia