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Meiosis Meiosis lecture notes Timed quiz Micrographs Mitosis / meiosis

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Presentation on theme: "Meiosis Meiosis lecture notes Timed quiz Micrographs Mitosis / meiosis"— Presentation transcript:

1 Meiosis Meiosis lecture notes Timed quiz Micrographs Mitosis / meiosis
comparison

2 Interphase As with mitosis, DNA replication takes place during interphase before meiosis begins. Centrioles Nucleus

3 Prophase I Chromosomes condense
Centrioles duplicate and move towards poles Micrograph

4 Prophase I Chromosomes condense
Centrioles duplicate and move towards poles

5 Prophase I Chromosomes condense
Centrioles duplicate and move towards poles Nuclear membrane breaks down

6 Prophase I Nuclear membrane breaks down Micrograph

7 Prophase I Spindle begins to form
Homologous chromosomes pair up (synapsis) forming bivalents. Crossing over may occur between chromatids Detail of crossing over

8 Metaphase I Spindle begins to form Chromosomes line up on equator of
cell in homologous pairs (bivalents)

9 Metaphase I Chromosomes line up on equator of cell in homologous
pairs (bivalents) Micrograph

10 Anaphase I Chromosomes pulled to opposite ends of the cell
by spindle fibres

11 Anaphase I Chromosomes pulled to opposite ends of the cell
by spindle fibres Micrograph

12 Telophase I Nuclear membrane may reform (Chromosomes may recondense)
Micrograph

13 Telophase I In some organisms, cytokinesis
takes place at the end of telophase I

14 Prophase II In some organisms, cytokinesis
takes place at the end of telophase I

15 Prophase II Centrioles replicate Nuclear membrane breaks down

16 Metaphase II Centrioles move to poles of cells
Spindle forms; chromosomes line up on equator Micrograph

17 Anaphase II Centromeres divide, and chromatids are moved to
opposite ends of the cells by spindle fibres Micrograph

18 Telophase II

19 Telophase II Nuclear membranes reform Cytokinesis follows

20 Telophase II Nuclear membranes reform Cytokinesis follows

21 4 haploid cells Telophase II Nuclear membranes reform
Cytokinesis follows 4 haploid cells Micrograph

22 Meiosis animation Try to identify the different phases in this animation of meiosis

23 Random assortment If a cell with two pairs of chromosomes undergoes meiosis there are four possible combinations of chromosomes in the gametes produced.

24 Random assortment How many possible combinations of chromosomes are there in human gametes with 23 pairs of chromosomes? 223 =

25 DNA replicates during interphase
Crossing over

26 DNA replicates during interphase
Crossing over

27 Crossing over DNA replicates during interphase
During prophase I chromatids break and reconnect to a different chromatid in the bivalent Crossing over

28 Crossing over DNA replicates during interphase
During prophase I chromatids break and reconnect to a different chromatid in the bivalent This results in different combinations of alleles on the chromosomes Crossing over

29 Crossing over DNA replicates during interphase
During prophase I chromatids break and reconnect to a different chromatid in the bivalent This results in different combinations of alleles on the chromosomes Crossing over

30 Chiasmata Crossing over
The point on a chromosome where crossing over takes place is described as a chiasma (plural: chiasmata). One or more chiasmata may form anywhere along the length of the two chromosomes involved in crossing over. Chiasmata Back to metaphase I

31 Meiosis overview

32 There are eight questions.
Meiosis quiz You will need a pen and paper. You have ten seconds to answer each question. Answers are shown at the end. There are eight questions. Start

33 1. Which stage of meiosis is this?

34 2. Which of these diagrams shows anaphase I of meiosis?
B C D

35 3. At which stage of meiosis does crossing over happen?
Telophase II Anaphase I Metaphase I Metaphase II Prophase I

36 4. Which stage of meiosis is this?

37 5. Which of these micrographs shows late anaphase II?
B C D

38 6. Crossing over results in new combinations of:
Alleles Chromosomes Chromatids Bivalents

39 7. Which of these stages of meiosis is telophase II?
B C D

40 8. Which stage of meiosis is shown on this micrograph?

41 View questions again Answers

42 1. Which stage of meiosis is this?
Metaphase II

43 2. Which of these diagrams shows anaphase I of meiosis?
B C D

44 3. At which stage of meiosis does crossing over happen?
Telophase II Anaphase I Metaphase I Metaphase II Prophase I

45 4. Which stage of meiosis is this?
Telophase I

46 5. Which of these micrographs shows late anaphase II?
B C D

47 6. Crossing over results in new combinations of:
Alleles Chromosomes Chromatids Bivalents

48 7. Which of these stages of meiosis is telophase II?
B C D

49 8. Which stage of meiosis is shown on this micrograph?
Metaphase II

50 Meiosis Meiosis lecture notes Timed quiz Micrographs Mitosis / meiosis
comparison

51 Prophase I Return to notes

52 Prophase I Return to notes

53 Metaphase I Return to notes

54 Anaphase I Return to notes

55 Telophase I Return to notes

56 Metaphase II Return to notes

57 Anaphase II Return to notes

58 Telophase I Return to notes

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