1. Meiosis and Genetics

2. Cell Division All cells are derived from pre-existing cells
New cells are produced for growth and to replace damaged or old cells
Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals)

3. Mitosis in 3 stages Interphase Duplication of DNA and cell growth
Division of genetic material
Cytokinesis
Division of Cytoplasm

4. Let’s Practice!
2. Prophase: Centrioles travel to opposite ends; Spindles form
4. Anaphase: Sister Chromatids are pulled apart
1. Interphase: DNA duplicates; Cell grows
3. Metaphase: Sister chromatids line up in the middle of the cell
6. Cytokinesis: Cytoplasm divides; Creates 2 identical daughter cells
5. Telophase: Nuclear membrane reappears; cells begin to split

5. Asexual Cell Reproduction

6. Types of Cell Reproduction
Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells
Mitosis & Binary fission are an example of asexual reproduction

7. Eukaryotic Asexual Division
Used for growth and repair
Produce two new cells identical to the original cell
Cells are diploid (2n)
Chromosomes during Metaphase of mitosis
Cytokinesis
Anaphase
Prophase
Metaphase
Telophase

8. Asexual Reproduction in Prokaryotes AKA Binary Fission

9. Cell Division in Prokaryotes
Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission
Single chromosome makes a copy of itself
Cell wall forms between the chromosomes dividing the cell
Parent cell
Chromosome replicates
Cell splits
2 identical daughter cells

10. Prokaryotic Cell Undergoing Binary Fission

11. Meiosis Formation of Gametes (Eggs & Sperm)

12. Types of Cell Reproduction
Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells
Meiosis is an example

13. Why Do we Need Meiosis?
It is the fundamental basis of sexual reproduction
Two haploid gametes are brought together through fertilization to form a diploid zygote

14. Fertilization – “Putting it all together”

15. A Replicated Chromosome
Gene – Blue Eyes
Sister Chromatids
Homologs-
chromosomes with the same genes in matching locations
chromatids with matching genes in matching locations
Gene – Brown Eyes
Homologs- These homologous pairs line up next to each other and are known as tetrads.

16. Meiosis Forms Haploid Gametes
Meiosis must reduce the chromosome number by half
Fertilization then restores the diploid (2n) number
from mom
from dad
child
too
much!
meiosis reduces
genetic content
The right number!

17. Meiosis: Two Part Cell Division
Sister
chromatids
separate
Meiosis I
Meiosis II
Homologs
separate
Diploid
Haploid
Haploid

18. Results of Meiosis Gametes (egg & sperm) form
Four haploid cells with one copy of each chromosome
One copy of each gene
Different combinations for alleles for different genes along the chromosome

19. Homologous Chromosomes During Crossing-Over

20. Crossing-Over Homologous chromosomes in a tetrad cross over each other
Pieces of chromosomes or genes are exchanged
Produces Genetic recombination in the offspring

21. Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment

22. Comparing Mitosis and Meiosis

23. Comparison of Divisions
Mitosis
Meiosis
Number of divisions 1 2
Number of daughter cells 4
Genetically identical?
Yes No
Chromosome #
Same as parent
Half of parent
Where
Somatic cells
Sex cells within gonads
When
Throughout life
At sexual maturity
Role
Growth and repair; Asexual reproduction
Sexual reproduction

24. Why be different? Asexual Sexual Pros Cons Pros Cons Fast, efficient
If genes are desirable, genetically identical offspring are strong and able to survive
Cons
If genes are weak, genetically identical offspring have no chance of survival
One disease could wipe out a population
Pros
Genetic variation ensures the survival of part of the species
Allows for emergence of new traits in the theory of evolution
Cons
Genetic mutations could cause deficiencies in organisms
Quality traits are not always passed down through generations

25. Facts About Meiosis
Preceded by Interphase which includes chromosome replication
Two meiotic divisions --- Meiosis I and Meiosis II
Original cell is diploid

26. Facts About Meiosis
Daughter cells contain half the number of chromosomes as the original cell
Produces gametes; sex cells (eggs & sperm)
Occurs in the testes in males (Spermatogenesis)
Occurs in the ovaries in females (Oogenesis)

27. More Meiosis Facts After 1 division - 23 double stranded chromosomes
Start with 46 double stranded chromosomes
After 1 division - 23 double stranded chromosomes
After 2nd division - 23 single stranded chromosomes
  Occurs in our sex cells that produce gametes

28. Karyotype
A picture of the chromosomes from a human cell arranged in pairs by size
First 22 pairs are called autosomes
Last pair are the sex chromosomes
XX female or XY male

29. Mendelian Genetics
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Mendelelian Genetics

30. Responsible for the Laws of Inheritance
Mendelian Genetics
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Gregor Mendel ( )
Responsible for the Laws of Inheritance

31. Mendelian Genetics
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Gregor Johann Mendel
Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants
He found that the plants' offspring retained traits of the parents
Called the “Father of Genetics"

32. Mendelian Genetics
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Genetic Terminology
Trait - any characteristic that can be passed from parent to offspring
Heredity - passing of traits from parent to offspring
Genetics - study of heredity

33. Types of Genetic Crosses
Mendelian Genetics
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Types of Genetic Crosses
Monohybrid cross - cross involving a single trait e.g. flower color
Dihybrid cross - cross involving two traits e.g. flower color & plant height

34. Designer “Genes” Alleles - two forms of a gene (dominant & recessive)
Mendelian Genetics
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Designer “Genes”
Alleles - two forms of a gene (dominant & recessive)
Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R)
Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r)

35. Mendelian Genetics
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More Terminology
Genotype - gene combination for a trait (e.g. RR, Rr, rr)
Phenotype - the physical feature resulting from a genotype (e.g. red, white)

36. Genotype & Phenotype in Flowers
Mendelian Genetics
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Genotype & Phenotype in Flowers
Genotype of alleles: R = red flower r = yellow flower
All genes occur in pairs, so 2 alleles affect a characteristic
Possible combinations are:
Genotypes RR Rr rr
Phenotypes RED RED YELLOW

37. Mendelian Genetics
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Genotypes
Homozygous genotype - gene combination involving 2 dominant or 2 recessive genes (e.g. RR or rr); called pure 
Heterozygous genotype - gene combination of one dominant & one recessive allele (e.g. Rr); called hybrid

38. Punnett Square Used to help solve genetics problems Mendelian Genetics
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Punnett Square
Used to help solve genetics problems

39. Mendelian Genetics
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40. Mendelian Genetics
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Monohybrid Crosses

41. P1 Monohybrid Cross r r Rr Rr R R Rr Rr Trait: Seed Shape
Mendelian Genetics
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P1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Wrinkled seeds
RR x rr
Genotype: Rr
Phenotype: Round
Genotypic Ratio: All alike
Phenotypic Ratio: All alike r r Rr Rr R R Rr Rr

42. F1 Monohybrid Cross R r RR Rr R r Rr rr Trait: Seed Shape
Mendelian Genetics
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F1 Monohybrid Cross
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Round seeds
Rr x Rr
Genotype: RR, Rr, rr
Phenotype: Round & wrinkled
G.Ratio: 1:2:1
P.Ratio: 3:1 R r RR Rr R r Rr rr

43. Mendelian Genetics
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Practice Your Crosses

44. Mendelian Genetics
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Mendel’s Laws

45. Results of Monohybrid Crosses
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Results of Monohybrid Crosses
Inheritable factors or genes are responsible for all heritable characteristics
Phenotype is based on Genotype
Each trait is based on two genes, one from the mother and the other from the father
True-breeding individuals are homozygous (both alleles) are the same

46. Mendelian Genetics
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Law of Dominance
In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.
Therefore…offspring that are heterozygous will express only the dominant trait.
RR x rr yields all Rr (round seeds)

47. Mendelian Genetics
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Law of Segregation
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.

48. Applying the Law of Segregation
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Applying the Law of Segregation

49. Law of Independent Assortment
Mendelian Genetics
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Law of Independent Assortment
Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
This law can be illustrated using dihybrid crosses.

50. Mendelian Genetics
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Dihybrid Cross
A breeding experiment that tracks the inheritance of two traits.
Mendel’s “Law of Independent Assortment”
Each pair of alleles segregates independently during gamete formation

51. All possible gamete combinations
Mendelian Genetics
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Dihybrid Cross
Traits: Seed shape & Seed color
Alleles: R round r wrinkled Y yellow y green
RrYy x RrYy
RY Ry rY ry
RY Ry rY ry
All possible gamete combinations

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

53. Summary of Mendel’s laws
Mendelian Genetics
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Summary of Mendel’s laws
LAW
PARENT CROSS
OFFSPRING
DOMINANCE
TT x tt tall x short
100% Tt tall
SEGREGATION
Tt x Tt tall x tall
75% tall 25% short
INDEPENDENT ASSORTMENT
RrGg x RrGg 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

54. Incomplete Dominance and Codominance
Mendelian Genetics
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Incomplete Dominance and Codominance

55. Mendelian Genetics
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Incomplete Dominance
Hybrids have an appearance somewhat in between the phenotypes of the two parental varieties.
Example: snapdragons (flower)
red (RR) x white (rr)
RR = red flower
rr = white flower r R

56. Incomplete Dominance r R r All Rr = pink (heterozygous pink)
Mendelian Genetics
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Incomplete Dominance r R r
All Rr = pink
(heterozygous pink)
produces the
mixed generation Rr

57. Mendelian Genetics
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Codominance
Two alleles are expressed at the same time in heterozygous individuals.
Example: blood type
1. type A = IAIA or IAi
2. type B = IBIB or IBi
3. type AB = IAIB
4. type O = ii

58. Codominance Problem Example: male Type A (IAIA) x female type B (IBIB)
Mendelian Genetics
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Codominance Problem
Example: male Type A (IAIA) x female type B (IBIB) IB IA
IAIB
All = IAIB

59. Sex-linked Traits Traits (genes) located on the sex chromosomes
Mendelian Genetics
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Sex-linked Traits
Traits (genes) located on the sex chromosomes
Sex chromosomes are X and Y
XX genotype for females
XY genotype for males
Many sex-linked traits carried on X chromosome

60. Sex-linked Traits Example: Eye color in fruit flies Sex Chromosomes
Mendelian Genetics
9/7/2018
Sex-linked Traits
Example: Eye color in fruit flies
Sex Chromosomes
XX chromosome - female
Xy chromosome - male
fruit fly
eye color

61. Sex-linked Trait Problem
Mendelian Genetics
9/7/2018
Example: Eye color in fruit flies
(red-eyed male) x (white-eyed female) XRY x XrXr
Remember: the Y chromosome in males does not carry traits.
RR = red eyed
Rr = red eyed
rr = white eyed
XY = male
XX = female XR Xr Y

62. Sex-linked Trait Solution:
Mendelian Genetics
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Sex-linked Trait Solution: XR Xr Y
50% red eyed female
50% white eyed male
XR Xr
Xr Y

63. Genotype of a Normal Male
Mendelian Genetics
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Female Carriers
Genotype of a Normal Male
Genotype of a Female Carrier

64. Pedigree