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Meiosis lecturenotes
Timed quiz
Micrographs
Mitosis / meiosiscomparison
As with mitosis, DNA replication takes place during interphase before meiosis begins.
As with mitosis, DNA replication takes place during interphase before meiosis begins.
Nucleus
Centrioles
Chromosomes condenseCentrioles duplicate and move towards poles
Chromosomes condenseCentrioles duplicate and move towards poles
Micrograph
Chromosomes condenseCentrioles duplicate and move towards poles
Chromosomes condenseCentrioles duplicate and move towards poles
Chromosomes condenseCentrioles duplicate and move towards poles
Chromosomes condenseCentrioles duplicate and move towards poles
Nuclear membranebreaks downNuclear membranebreaks down
Nuclear membranebreaks downNuclear membranebreaks down
Micrograph
Spindle begins to formSpindle begins to form
Detail of crossing over
Homologous chromosomes pair up (synapsis) forming bivalents.Crossing over may occur between chromatids
Homologous chromosomes pair up (synapsis) forming bivalents.Crossing over may occur between chromatids
Spindle begins to formSpindle begins to form
Chromosomes lineup on equator of cell in homologouspairs (bivalents)
Chromosomes lineup on equator of cell in homologouspairs (bivalents)
Chromosomes lineup on equator of cell in homologouspairs (bivalents)
Chromosomes lineup on equator of cell in homologouspairs (bivalents)
Micrograph
Chromosomes pulled to opposite ends of the cell by spindle fibres
Chromosomes pulled to opposite ends of the cell by spindle fibres
Chromosomes pulled to opposite ends of the cell by spindle fibres
Chromosomes pulled to opposite ends of the cell by spindle fibresMicrograph
Nuclear membrane may reform (Chromosomes may recondense)
Nuclear membrane may reform (Chromosomes may recondense)
Micrograph
In some organisms, cytokinesistakes place at the end of telophase IIn some organisms, cytokinesistakes place at the end of telophase I
In some organisms, cytokinesistakes place at the end of telophase IIn some organisms, cytokinesistakes place at the end of telophase I
Centrioles replicateNuclear membrane breaks downCentrioles replicateNuclear membrane breaks down
Centrioles move to poles of cellsSpindle forms; chromosomes line up on equator
Centrioles move to poles of cellsSpindle forms; chromosomes line up on equator
Micrograph
Centromeresdivide, and chromatidsare moved toopposite endsof the cells byspindle fibres
Centromeresdivide, and chromatidsare moved toopposite endsof the cells byspindle fibres
Micrograph
Nuclear membranes reformCytokinesis followsNuclear membranes reformCytokinesis follows
Nuclear membranes reformCytokinesis followsNuclear membranes reformCytokinesis follows
Nuclear membranes reformCytokinesis followsNuclear membranes reformCytokinesis follows
Micrograph
Meiosis animation
Try to identify the different phases in this animation of meiosis
Try to identify the different phases in this animation of meiosis
If a cell with two pairs of chromosomes undergoes meiosis there are four possible combinations of chromosomes in the gametes produced.
If a cell with two pairs of chromosomes undergoes meiosis there are four possible combinations of chromosomes in the gametes produced.
How many possible combinations of chromosomes are there in human gametes with 23 pairs of chromosomes?
How many possible combinations of chromosomes are there in human gametes with 23 pairs of chromosomes?
2223 23 == 83886088388608
DNA replicates during interphase
DNA replicates during interphase
DNA replicates during interphase
During prophase I chromatids break and reconnect to a different chromatid in the bivalent
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
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
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.
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.
ChiasmataChiasmata
Back to metaphase I
Meiosis quizMeiosis quizYou 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
1. Which stage of meiosis is this?
2. Which of these diagrams shows anaphase I of meiosis?
A B
C D
3. At which stage of meiosis does crossing over
happen?
A. Telophase II
B. Anaphase I
C. Metaphase I
D. Metaphase II
E. Prophase I
4. Which stage of meiosis is this?
5. Which of these micrographs shows late
anaphase II?A
DC
B
6. Crossing over results in new combinations of:
A. Alleles
B. Chromosomes
C. Chromatids
D. Bivalents
7. Which of these stages of meiosis is telophase II?
A B
C D
8. Which stage of meiosis is shown on this micrograph?
View questions againView questions again
AnswersAnswers
1. Which stage of meiosis is this?
Metaphase IIMetaphase II
2. Which of these diagrams shows anaphase I of meiosis?
A B
C D
3. At which stage of meiosis does crossing over
happen?
A. Telophase II
B. Anaphase I
C. Metaphase I
D. Metaphase II
E. Prophase I
4. Which stage of meiosis is this?
Telophase ITelophase I
5. Which of these micrographs shows late
anaphase II?A
D
B
C
6. Crossing over results in new combinations of:
A. Alleles
B. Chromosomes
C. Chromatids
D. Bivalents
7. Which of these stages of meiosis is telophase II?
A B
C D
8. Which stage of meiosis is shown on this micrograph?
Metaphase IIMetaphase II
Meiosis lecturenotes
Timed quiz
Micrographs
Mitosis / meiosiscomparison
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