1. Find someone with the opposite color paper.
Use your notes to come with anything you remember about mitosis:
Purpose
What you start with, what you end up with
Are the daughter cells identical to or different from the parent cells?
4 phases? What happens in them (keep it simple)
Mitosis Review First!

2. Meiosis

3. What differences do you notice?
Asexual
Sexual 46 23 46 46 46

4. 2 Types of Reproduction 1. Asexual
One parent produces genetically identical offspring
Ex: Body cells (during mitosis) & bacteria
No genetic diversity!
2. Sexual
Two parents produce genetically different offspring through fertilization
Uses meiosis – type of cell division used to create gametes (egg & sperm)
Produces genetic variation

5. Budding
Binary Fission

6. Genetic Variation (diversity)
Differences in DNA = differences in our traits
Need variation
If habitat changes, populations are more likely to survive if traits/skills are varied

7. Haploid (n or 1n) Haploid (n) – cell that has 1 set of chromosomes
n = # of chromosomes
Gametes/sex cells (egg & sperm) are haploid chromosomes
Meiosis- type of cell division used to make haploid cells

8. Haploid

9. Haploid vs. DIploid

10. Haploid vs. diploid Diploid (2n)
- cell that contains 2 sets or pairs of chromosomes (1 from mom and dad)
Referred to as 2n
2x haploid #

11. Contains homologous pairs of chromosomes Analogy- like pairs of shoes
Somatic (body) cells are diploid  46 chromosomes or 23 pairs
Contains homologous pairs of chromosomes
Analogy- like pairs of shoes

12. DIploid

13. Homologous Chromosomes
Pairs of chromosomes that are the same size, shape and gene pattern
Made of 2 chromatids
They are NOT identical  one from each parent
Ex: 2 Chromosome 10’s

16. C4U

17. Why Meiosis?
Purpose: Sexual reproduction (make gametes) and to create genetic diversity/variation
Location: Reproductive organs/cells
Produces: 4 genetically unique, haploid (gametes)
Variation from crossing over (prophase I) & independent assortment (metaphase I)

18. Process of Meiosis Meiosis occurs in 2 rounds- Meiosis 1 and meiosis 2
Before Meiosis I, DNA replication occurs
Human cell: Normally 23 pairs  46 pairs before Meiosis starts (92 total)
McGraw Hill Animation

19. Meiosis I
Purpose: To create genetic diversity variation and reduce chromosome number in half

20. Meiosis I – Prophase I
Synapsis occurs – when homologous chromosomes line up next to each other forming tetrads
Tetrads- pair of homologous chromosomes ( 4 chromatids) (2n)

21. Remember!
Chromatid = ½ of a chromosome

22. Meiosis I – Prophase I
Crossing over occurs – exchange genetic info by exchanging matching sections of chromatids
This produces genetic diversity and unique chromatids (2n)
Crossing Over
CC 4-6:30

24. Tetrads vs homologous chromosomesX
Homologous chromosome
- 2 chromatids

25. This again causes genetic diversity
Metaphase I
Independent assortment occurs – when the tetrads line up randomly at metaphase plate
This again causes genetic diversity
Independent assortment

27. Tetrads separate to opposite ends of cell
Anaphase I
Tetrads separate to opposite ends of cell

28. Telophase I Cell splits into 2 diploid cells
Remember we started with 46 pairs (92 total) chromosomes  now we have 23 pairs (46 total) in each cell
The cells are NOT identical – Why??

29. Why do we still need meiosis II?
Because the chromosomes are still replicated  sister chromatids (46 chromosomes) . We need individual chromatids in gametes

31. Answer these questions in notebook
1. What’s the purpose or result of meiosis?
2. When does independent assortment occur?
3. When does crossing over occur?
4. How does meiosis introduce genetic diversity?
5. What has to happen before meiosis can occur?

33. Meiosis II The 2 diploid cells are divided- like mitosis
Produces: 4 haploid cells, each containing a single copy of each chromosome
Those haploid cells are the egg & sperm cells

34. Meiosis II – Prophase II
No crossing over
Sister chromatids are still replicated
Nuclear membrane disappears again

35. Metaphase II
Sister chromatids line up at metaphase plate

36. ANAphase II
Sister chromatids separate

37. TeloPHASE II
McGraw Hill Animation
Cells split, producing 4 genetically unique haploid daughter cells

38. Meiosis I vs. Meiosis II During Meiosis I _____________________
divide.
During Meiosis II _____________________
divide
Metaphase 1
Anaphase 1
Homologous chromosomes
Sister chromatids
Metaphase 2
Anaphase 2

39. Comparing Mitosis and Meiosis

40. Comparing Mitosis and Meiosis C4U
Produces identical daughter cells, produces unique daughter cells, occurs in eukaryotic cells, two round of cell division, one round of cell division, occurs in multi-cellular organisms, produces haploid cells, produces diploid cells, produces body cells, produces gametes, is a multi-step process, involves crossing-over and independent assortment

41. Produces identical daughter cells, (MT)
occurs in multi-cellular organisms, (B)
produces haploid cells, (MS)
produces diploid cells, (MT)
produces body cells, (MT)
produces gametes, (MS)
is a multi-step process, (B)
involves crossing-over and independent assortment (MS)
Produces identical daughter cells, (MT)
produces unique daughter cells, (MS)
occurs in eukaryotic cells, (B)
two round of cell division, (MS)
one round of cell division, (MT)

42. Mutations in Meiosis
Do mutations in body cells have an effect on the offspring? How about in sex cells? Explain.
Body cells  only affect cells produced from mitosis from this cell
Sex cells  Used to make offspring; mutations are passed on

43. Are most of the genetic differences in the world attributed to mutations or shuffling DNA in meiosis?

44. This picture shows a type of mistake that can occur during meiosis.
On your paper write down what you think is happening.

45. This can result in gametes that have too many or too few chromosomes.
Non-disjunction is an error during meiosis in which the chromosomes fail to separate properly.
This can result in gametes that have too many or too few chromosomes.
Step-through Mistakes in Meiosis Animation

46. Nondisjunction can be detected through a Karyotype.
A Karyotype is - a picture of one’s 46 chromosomes.
It allows us to detect abnormal numbers of chromosomes as well as chromosomal mutations.

47. Healthy Female: 46 chromosomes  XX
Healthy Male: 46 chromosomes  XY

48. Down Syndrome Trisomy 21- 3 copies of the chromosome 21
47 total chromosomes instead of 46
Caused by nondisjunction
Effects:
Characteristic facial features, heart defects, susceptibility to leukemia & Alzheimer’s
Varying degrees of intellectual disability

49. Klinefelter’s Males with extra X chromosome Reduced facial & body hair
Breast enlargement
Infertility
Some learning disabilities and difficulty with speech

50. Jacob’s Syndrome Males with extra Y chromosome Taller than average
Learning or speech difficulties
Weaker bones or muscles

51. Turner’s syndrome Female with only 1X chromosome Short height
Lack hormones for menstruation and breast growth
Infertility
Drooping eye lids, low hair line
Kidney & heart problems, diabetes

53. Mitosis Meiosis Purpose Takes place in… Produces how many cells?
What happens to chromosome number?
How do parents and daughter cells differ genetically?
Variation between daughter cells?