Meiosis and Sexual Life Cycles

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Division in meiosis II also occurs in four phases:

– Prophase II

– Metaphase II

– Anaphase II

– Telophase II and cytokinesis

Meiosis II is very similar to mitosis

Slide 50

Fig. 13-8d

Prophase II

Metaphase II

Anaphase II

Telophase II and

Cytokinesis

Sister chromatids

separate

Haploid daughter cells

forming

Slide 51

Prophase II

In prophase II, a spindle apparatus forms

In late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate

Slide 52

Metaphase II

In metaphase II, the sister chromatids are arranged at the metaphase plate

Because of crossing over in meiosis I, the two sister chromatids of each chromosome are no longer genetically identical

The kinetochores of sister chromatids attach to microtubules extending from opposite poles

Slide 53

Fig. 13-8e

Prophase II

Metaphase II

Slide 54

Anaphase II

In anaphase II, the sister chromatids separate

The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles

Slide 55

Telophase II and Cytokinesis

In telophase II, the chromosomes arrive at opposite poles

Nuclei form, and the chromosomes begin decondensing

Slide 56

Cytokinesis separates the cytoplasm

At the end of meiosis, there are four daughter cells, each with a haploid set of unreplicated chromosomes

Each daughter cell is genetically distinct from the others and from the parent cell

Slide 57

Fig. 13-8f

Anaphase II

Telephase II and

Cytokinesis

Sister chromatids

separate

Haploid daughter cells

forming

Slide 58

A Comparison of Mitosis and Meiosis

Mitosis conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell

Meiosis reduces the number of chromosomes sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell

The mechanism for separating sister chromatids is virtually identical in meiosis II and mitosis

Slide 59