Reproduction & Embryology

Diploid and Haploid Cells

DiploidHaploid # of chromosomes4623 # of pairs230 FunctionMaintain lifeSexual Reproduction LocationSomatic (throughout body) Gamete (gonads – reprodcuctive organs)

Homologous Chromosomes

DiploidHaploid Brain Cell46 Skin Cell46 Sperm23

Different Methods of Division MitosisMeiosis # of chromosomes in parent cell 46 # of chromosomes in daughter cell 4623 # of pairs in parent cell2346 # of pairs in daughter cell230 Daughter cells are identical to… Parent cell and each otherNothing – they are different from parent and each other

Fertilization

Based on Figure 4, what process creates the egg and sperm? meiosis Based on Figure 4, what is fertilization? Uniting of the sperm and egg Fertilization results in a zygote. A zygote is a single cell, yet a baby is millions of cells. What process creates those millions of cells? mitosis How does meiosis and fertilization creates unique individuals? Meiosis creates unique sperm and eggs Fertilization randomly combines them How does meiosis and fertilization ensure that the amount of genetic information in the zygote is the same as in each body cell of the parents? Meiosis creates haploid cells Fertilization combines two haploid cells

Diploid and Haploid Cells # of Chromosomes# of Pairs Liver Cell in adult4623 Zygote4623 Egg230 Sperm230 Brain cell in embryo4623

Reproduction & Embryology

The cell cycle remains the same except… G1 S G2 Division: meiosis & cytokinesis

Meiosis instead of Mitosis Occurs Meiosis is a different way to divide the nucleus – it divides it in half literally – creating nuclei with 23 chromosomes instead of 46!

Prophase I Prophase I is the longest and most complex phase. All of the events that occurred during prophase of mitosis occur + Homologous chromosomes come together to form a SYNAPSE (TETRAD). CROSSING-OVER occurs.

Prophase I Crossing Over Mixed Up DNA!

Metaphase I

Anaphase I

Telophase I / Cytokinesis

Meiosis II Meiosis II comes directly after cytokinesis. No growth (interphase) takes place. Meiosis II is broken into 4 events: prophase II metaphase II anaphase II telophase II. The steps of Meiosis II are identical to mitosis.

Prophase II Prophase II is the same as prophase in mitosis.

Metaphase II Metaphase II is the same as metaphase in mitosis.

Anaphase II Anaphase II is the same as anaphase in mitosis. Notice that the sister chromatids separate.

Telophase II