cell cycle

·       Interphase occurs. G₁ cell grows.  DNA is replicated during S. 1 chromosome is now made of 2 sister chromatids. G₂ prep.

·       Meiosis I – Reduction DIVISION. IT IS ALL ABOUT THE HOMOLOGOUS CHROMOSOMES

·       Prophase I– Reduction division step. Diploid cell will end up as a haploid cell. Recombination of genetic material due to crossing over!!!!!!!         HOW CAN YOU TELL? Look at the cell and notice how the chromosomes are in the X shape (sister chromatids) and that two colors are being used. One color represents each inherited chromosome (mom and dad DNA). The two Xs (like a blue and a red of the same length) are moving towards each other. Crossing over happens and now one X is part blue/red and the other X is part blue/red (Or another mix of two colors; the mix indicates DNA was swapped during crossing over and that recombinant chromosomes have been made).

·       Metaphase I – Recombinant homologous chromosomes are lined up in the middle. HOW CAN YOU TELL? Look for 2 columns of X. Each X will be made of a different color and SHOULD be made of two colors.

·       Anaphase I - Recombinant homologous chromosomes are moving AWAY from each other towards opposite poles. HOW CAN YOU TELL? Look for a column of Xs on one side of the cell and another column of Xs on the other side of the cell. The two columns have some Xs of each color.

·       Telophase II – The cell now has two nuclei. In each nucleus you see X shapes (chromosomes with sister chromatids). HOW CAN YOU TELL?  Each nucleus has half the amount of DNA that you saw in interphase. Chromosomes are in X shape. One chromosome has two colors in it because it is now a recombinant chromosome.

·       CYTOKINESIS – Cell splits into two cells. You started with 1 cell diploid. Now you have 2 cells and each is haploid. This is why meiosis I is called reduction division.

·       Meiosis II – You have two cells now and BOTH are going through meiosis II. There is no interphase before meiosis II. You have a recombinant chromosome with 2 sister chromatids. Meiosis II is all about the non-identical sister chromatids (due to crossing over in prophase I) getting separated.

·       Prophase II – NO CROSSING OVER!!!! Nuclear envelope breaks

·       Metaphase II – One line of X down the center of the cell. WATCH!!!! The X is made of 2 colors indicate crossing over occurred during prophase I

·       Anaphase II – Two line of “l” moving away from each other. WATCH!!!! The “l” sister chromatid moving away from the “l” sister chromatid are not identical.

·       Telophase II – Two nuclei

·       SECOND Cytokinesis – Now you have 4 cells that are haploid with recombinant chromosomes. Images may show a total of 4 cells.