1. Chapter 13- Meiosis

2. QQ 10/5/18 Copy the following into notebook:
Similarities:
Differences:

3. Figure 13.1
Figure 13.1 What accounts for family resemblance?

5. Living organisms are distinguished by their ability to reproduce their own kind
Transmission of traits from one generation to another- inheritance, or heredity
With inheritance there are both similarities and differences.
Genetics is the study of heredity and variation

6. Parents endow their offspring with genes- heredity “units” of DNA
-Tens of thousands passed on to offspring
-All the genes compose the genome
Human Genome Project (2000)
Human gene mapping of major genetic conditions
Cystic Fibrosis Gene

7. *sperm/egg (pollen/egg)
Gametes- the cells used by plants and animals to pass on their genetic info
*sperm/egg (pollen/egg)
All genes can be found at a specific, corresponding location- Locus
Locus point is specific and identified with designated (p, q, letters/numbers)

8. Information on paired genes from each parent (specific locus point)

9. Asexual reproduction- A single individual is a parent and passes on ALL of its genetic information by mitosis to a clone.
Can be single or multicellular organism.
Variation in family lines is caused by mutations.

10. 0.5 mm Parent Bud (a) Hydra (b) Redwoods Budding in a Hydra
Figure 13.2
0.5 mm
Parent
Bud
Figure 13.2 Asexual reproduction in two multicellular organisms.
(a) Hydra
(b) Redwoods
Budding in a Hydra

11. These pairs are called homologous chromosomes or autosomes
Sexual reproduction- Variation is caused by both parents passing on a set of their genetic information that then combines.
Meiosis *Makes GAMETES only
Karyotyping- Matching up pairs of chromosomes from longest to shortest.
These pairs are called homologous chromosomes or autosomes
*in humans, homologous pairs #1-22 are the autosome; #23 are sex chromosomes- not considered homologous! (XX or XY)

12. Pair of homologous duplicated chromosomes
Figure 13.3
APPLICATION
TECHNIQUE
5 m
Pair of homologous duplicated chromosomes
Centromere
Figure 13.3 Research Method: Preparing a Karyotype
Sister chromatids
Metaphase chromosome

13. (humans on left; cat on right)
Karyotypes
(humans on left; cat on right)

14. A Dog’s Karyotype

15. There are also two distinct chromosomes that might not match- sex chromosomes
- Male- XY- Smaller amount of DNA
- Sperm can either be X or Y
- Female- XX
- Egg is ALWAYS X

16. sex chromosome combinations possible in the new individual
diploid
germ cells
in female
diploid
germ cells
in male
meiosis, gamete
formation in both
female and male:
eggs
sperm X × Y X × X
fertilization: X X X XX XX Y XY XY
sex chromosome combinations
possible in the new individual
Fig. 11.2, p.170

17. Q.Q. 10/8/18
If a cat’s liver cell in has 36 autosomes and XX sex chromosomes, how many chromosomes will be found in the gamete?
36 autosomes and XX in the egg cell
36 autosomes and XY in the sperm cell
18 autosomes and X in the egg cell
18 autosomes and Y in the sperm cell
None of the above

18. Q.Q. 10/8/18
If a cat’s liver cell in has 36 autosomes and XX sex chromosomes, how many chromosomes will be found in the gamete?
36 autosomes and XX in the egg cell
36 autosomes and XY in the sperm cell
18 autosomes and X in the egg cell
18 autosomes and Y in the sperm cell
None of the above

19. Chapter 13- Meiosis
Haploid cell (n)- Single set of chromosomes (in humans, n=23). Offspring receive one set from maternal (egg) side, another from paternal (sperm)
Diploid cell (2n)- BOTH sets of chromosomes (in humans, 2n= 46)
Cat n=? 2n=? Dog n=? 2n=?

20. Chromosome numbers: Ploidy = number of copies of each chromosome.
Diploidy- diploid (2n) sets of homologous chromosomes!
Tetraploid = 4n
All even, as all are diploid, contain pairs of chromosomes.

21. Ploidy

22. Mitosis and development
Haploid gametes (n  23)
Key
Haploid (n)
Egg (n)
Diploid (2n)
Sperm (n)
MEIOSIS
FERTILIZATION
Ovary
Testis
Diploid zygote (2n  46)
Figure 13.5 The human life cycle.
Mitosis and development
Multicellular diploid adults (2n  46)

24. The only cells not produced by mitosis are the gametes
Life Cycle begins when egg meets sperm and is fertilized (forms the zygote)
- Zygote is diploid (2n)
The only cells not produced by mitosis are the gametes
AFTER FERTILIZATION = The zygote produces more somatic cells by mitosis and develops into an adult

25. Maternal set of chromosomes (n  3)
Figure 13.4
Key
Key
Maternal set of chromosomes (n  3)
2n  6
Paternal set of chromosomes (n  3)
Sister chromatids of one duplicated chromosome
Centromere
Figure 13.4 Describing chromosomes.
Two nonsister chromatids in a homologous pair
Pair of homologous chromosomes (one from each set)

26. The Variety of Sexual Life Cycles
The alternation of meiosis and fertilization is common to all organisms that reproduce sexually
The three main types of sexual life cycles differ in the timing of meiosis and fertilization
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27. 3 main types of sexual life cycles
Figure 13.6
3 main types of sexual life cycles
Key
Haploid (n)
Haploid multi- cellular organism (gametophyte)
Haploid unicellular or multicellular organism
Diploid (2n) n
Gametes n n
Mitosis n
Mitosis
Mitosis n
Mitosis n n n n n
MEIOSIS
FERTILIZATION
Spores n n
Gametes n
Gametes
MEIOSIS
FERTILIZATION
Zygote
MEIOSIS
FERTILIZATION 2n 2n 2n
Diploid multicellular organism (sporophyte) 2n
Zygote
Diploid multicellular organism 2n
Mitosis
Mitosis
Figure 13.6 Three types of sexual life cycles.
Zygote
(a) Animals
(b) Plants and some algae
(c) Most fungi and some protists

28. Diploid multicellular organism Mitosis
Figure 13.6a
Key
Haploid (n)
Diploid (2n) n
Gametes n n
MEIOSIS
FERTILIZATION
Zygote 2n 2n
Figure 13.6 Three types of sexual life cycles.
Diploid multicellular organism
Mitosis
(a) Animals

29. Haploid multi- cellular organism (gametophyte)
Figure 13.6b
Key
Haploid (n)
Diploid (2n)
Haploid multi- cellular organism (gametophyte)
Mitosis n
Mitosis n n n n
Spores
Gametes
MEIOSIS
FERTILIZATION
Figure 13.6 Three types of sexual life cycles. 2n
Moss reproduction video
Diploid multicellular organism (sporophyte) 2n
Zygote
Mitosis
(b) Plants and some algae

30. Gametophyte makes haploid gametes by mitosis!
Key
The diploid organism, called the sporophyte, makes haploid spores by MEIOSIS.
Each spore grows by MITOSIS into a haploid organism called a gametophyte
Gametophyte makes haploid gametes by mitosis!
*already haploid so mitosis used to make more IDENTICAL haploid cells!
4) Fertilization of gametes results in a diploid sporophyte!
Haploid (n)
Diploid (2n)
Haploid multi- cellular organism (gametophyte)
2) Mitosis n
3) Mitosis n n n n
Spores
Gametes
1) MEIOSIS
4) FERTILIZATION
Figure 13.6 Three types of sexual life cycles. 2n
Diploid multicellular organism (sporophyte) 2n
Zygote
Mitosis
(b) Plants and some algae

31. Alteration of Generations (plants and algae)
Some plants undergo “alternation of generations”- has a diploid AND haploid multicellular stage of life
Diploid stage- Sporophyte = 2n (produces spores, which do not have to fuse to create offspring)
Haploid stage- Gametophyte= n (produces gametes)

32. Depending on the type of life cycle:
either haploid or diploid cells can divide by mitosis
However, only diploid cells can undergo meiosis!
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33. Steps of Meiosis VS. Mitosis Animation

34. KEY
DIFFERENCE!
Homologous
pairs
separate first

35. CROSSING
OVER!

36. Sister
Chromatids separate
at centromeres

37. Meiosis
Meiosis- reduces the number of chromosome sets from diploid to haploid
Two CONSECUTIVE cell divisions, Meiosis I and Meiosis II
4 daughter cells produced

38. Meiosis Interphase- Replication of genome and growth occur. *G1,S,G2
Centrosomes replicate
Meiosis stages (PMAT 1)
Prophase I- 90% of total time of meiosis
Chromosomes begin to condense
Homologous chromosomes pair and match up by gene (forming a tetrad)

40. Meiosis 1
Prophase 1
Crossing over- Where ever these homologous chromosomes match up, genetic information will switch to opposite chromosome
Centrosome movement toward poles of cell
Spindle formation and attachment of fibers
Breakdown of nuclear envelope

41. Meiosis 1 Metaphase I- Anaphase I- Sister chromatids remain attached
Tetrads arrange on the metaphase plate, spindle is fully attached
Anaphase I-
Homologous chromosomes separate and move toward poles
Sister chromatids remain attached

42. 2n=6

43. Meiosis 1 Telophase I and Cytokinesis I
Each cell will have sister chromatids
Splitting and cytokinesis *of cytoplasm; no nuclear envelope reforms because going right into Meiosis 2
Chromosomes might unwind, might not (depending on organism)

44. n=3 in each
n=3

45. Meiosis II Prophase II- Metaphase II- Anaphase II-
Spindle apparatus forms, movement of sisters towards metaphase plate
Metaphase II-
Spindle fibers attach to *centromere of sister chromatids at metaphase plate
Anaphase II-
Separation and migration of individual chromosomes toward poles
*Where sister chromatids separate and become separate individually counted chromosomes!

46. Meiosis II Telophase II and Cytokinesis II-
Nuclei form (*nuclear envelopes reform) and chromosomes unwind
*Cytoplasm divides (cleavage furrow/cell plate)

47. Meiosis (top) vs. mitosis (bottom)

48. What makes meiosis unique?
1) Synapses- process of attachment of homologous chromosomes
- Crossing Over- genetic rearrangement
- Chiasma (plural- chiasmata) – physical manifestation of crossing over

49. What makes meiosis unique?
2) Tetrads on metaphase plate *homologous chromosome pairs buddy up!
3) Separation of homologous chromosomes in Anaphase I, but sisters stay attached to each other

50. Trisomy 21- Cause of Down Syndrome
Nondisjunction animation

51. Three mechanisms contribute to genetic variation
Independent assortment of chromosomes
Crossing over
Random fertilization
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52. Genetic Variety
1) Independent Assortment of chromosomes- random orientation of homologous pairs at Metaphase I
- 50% of the homologous pair is maternal, 50% is paternal

53. Independent Assortment
Independent Assortment *various possibilities for arrangement of the homologous pairs (“assort” themselves) along metaphase plate

54. Independent Assortment
Which way is it going to be facing when “pulled” by the spindle?
Law of Independent Assortment basically says “every chromosome for himself”
To figure out how many possible combinations we can have, use 2n. *Humans = 223 = about 8 million combinations
*Dog=?

55. Independent assortment
Number of combinations: 2n
Why siblings can look completely different from one another!
e.g. 2 chromosomes in haploid
2n = 4; n = 2
2n = 22 = 4 possible combinations

56. Independent assortment

57. Three mechanisms that contribute to genetic variation (continued…)
2) Crossing Over- produces recombinant chromosomes (from multiple origins)
DNA is switched between maternal and paternal chromosomes *homologous pairs only! (*Chromosome 1 w/1, 2 w/2, etc.)
In humans there are roughly crossing over events per chromosome

58. Crossing Over

59. Three mechanisms that contribute to genetic variation (continued…)
3) Random Fertilization- The chance that you are sitting here is staggering.
- Paternal side 223, maternal side 223 and we then multiply = about 70 trillion : 1 (and this does NOT take into account crossing over events)

60. In humans… e.g. 23 chromosomes in haploid 2n = 46; n = 23
2n = 223 = ~ 8 million possible combinations!

61. Random fertilization
At least 8 million combinations from Mom, and another 8 million from Dad …
>70 trillion combinations for a diploid zygote!!!

62. Mitosis vs. Meiosis
Just meiosis!

63. Figure 13.9 A comparison of mitosis and meiosis in diploid cells.
Figure 13.9b
SUMMARY
Property
Mitosis
Meiosis
DNA replication
Occurs during interphase before mitosis begins
Occurs during interphase before meiosis I begins
Number of divisions
One, including prophase, metaphase, anaphase, and telophase
Two, each including prophase, metaphase, anaphase, and telophase
Synapsis of homologous chromosomes
Does not occur
Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion
Number of daughter cells and genetic composition
Two, each diploid (2n) and genetically identical to the parent cell
Four, each haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other
Figure 13.9 A comparison of mitosis and meiosis in diploid cells.
Role in the animal body
Enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction
Produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes

65. In mitosis, cohesins are cleaved at the end of metaphase
Sister chromatid cohesion allows sister chromatids of a single chromosome to stay together through meiosis I (Protein complexes called cohesins are responsible for this cohesion)
In mitosis, cohesins are cleaved at the end of metaphase
In meiosis, cohesins are cleaved along the chromosome arms in anaphase I (separation of homologs) and at the centromeres in anaphase II (separation of sister chromatids)
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66. Which of the following transmits genes from one generation of a family to another?
DNA
gametes
somatic cells
mitosis
nucleotides
Answer: b
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67. Which of the following transmits genes from one generation of a family to another?
DNA
gametes
somatic cells
mitosis
nucleotides
Answer: b
© 2011 Pearson Education, Inc.

68. Fertilization is to zygote as meiosis is to which of the following?
mitosis
diploid
chromosome
replication
gamete
Answer: e; discuss why

69. Fertilization is to zygote as meiosis is to which of the following?
mitosis
diploid
chromosome
replication
gamete
Answer: e; discuss why

70. Privet chromosomes undergo only mitosis.
Privet shrubs and humans each have a diploid number of 46 chromosomes per cell. Why are the two species so dissimilar?
Privet chromosomes undergo only mitosis.
Privet chromosomes are shaped differently.
Human chromosomes have genes grouped together differently.
The two species have different genes with different information.
Answer: d

71. Privet chromosomes undergo only mitosis.
Privet shrubs and humans each have a diploid number of 46 chromosomes per cell. Why are the two species so dissimilar?
Privet chromosomes undergo only mitosis.
Privet chromosomes are shaped differently.
Human chromosomes have genes grouped together differently.
The two species have different genes with different information.
Answer: d

72. meiosis I with the pairing of homologs
Independent Assortment At what stage do chromosomes undergo independent assortment? How?
meiosis I with the pairing of homologs
anaphase I with the separation of homologs
meiosis II with the separation of homologs
meiosis I with metaphase alignment
Answer: d

73. meiosis I with the pairing of homologs
Independent Assortment At what stage do chromosomes undergo independent assortment? How?
meiosis I with the pairing of homologs
anaphase I with the separation of homologs
meiosis II with the separation of homologs
meiosis I with metaphase alignment
Answer: d

74. Meiotic Phases In this cell, what phase is represented?
mitotic metaphase
meiosis I anaphase
meiosis I metaphase
meiosis II anaphase
meiosis II metaphase
Answer: c (see Figure 13.9)

75. release of cohesin along sister chromatid arms in anaphase I
Disjunction What allows sister chromatids to separate in which phase of meiosis?
release of cohesin along sister chromatid arms in anaphase I
crossing over of chromatids in prophase I
release of cohesin at centromeres in anaphase I
release of cohesin at centromeres in anaphase II
crossing over of homologues in prophase I
Answer: d

76. What are 3 ways in which gametes from one individual diploid cell can be different from one another?
Answer: mutation, crossing over, independent assortment

77. What are 3 ways in which gametes from one individual diploid cell can be different from one another? mutation, crossing over, independent assortment
Answer: mutation, crossing over, independent assortment

78. Rate and Process Prophase I of meiosis is generally the longest phase of meiosis. Why might this be?
Chromosomes must pair and crossover, besides the cell going through mitosis-like morphological changes.

79. SHOW ME MEIOSIS!