Meiosis

Question 1

prophase 1

Answer 1

Just like in mitosis, during prophase, DNA condensation occurs, the nuclear envelope and nucleoli disappear, and the spindle starts to form. The big difference is what is going on with the chromosomes themselves.

As DNA condensation proceeds and the chromosomes first become visible, they are visible as tetrads.  So, tetrads become visible during prophase.

Question 2

metaphase 1

Answer 2

Tetrads line up at the equator. The spindle has completely formed.

It is during prophase I and metaphase I that genetic recombination is occurring.  Take a look at the genetic recombination page to find out about how that happens here.  Keep in mind that it only happens when there are tetrads, so as soon as anaphase I gets going, genetic recombination is over.

Question 3

anaphase 1

Answer 3

Tetrads pull apart and chromosomes with two chromatids move toward the poles.

Question 4

telophase 1

Answer 4

Chromosomes with two chromatids decondense and a nuclear envelope reforms around them. Each nucleus is now haploid.

Question 5

prophase 2

Answer 5

Chromosomes with two chromatids become visible as they condense (and the nuclear envelope and nucleoli disappear, and the spindle is forming).

Question 6

metaphase 2

Answer 6

Chromosomes with two chromatids line up at the equator. The spindle is fully formed.

Question 7

anaphase 2

Answer 7

Chromosomes split, so that a chromosome with only one chromatid heads toward each pole.

Question 8

telophase 2

Answer 8

Chromosomes with only one chromatid decondense and get surrounded by new nuclear envelopes. The four daughter cells are now all haploid and have the right amount of DNA. They are ready to develop into sperm or eggs now.