Table of contents Intro to Bio Notes Page # Types of Biology Activity Page # Body System NotesPage # food Journal (3 pages)Page #- Page # Digestion NotesPage # Biomolecules NotesPage # Cardio Vascular NotesPage # Daphnia Lab- Data and proceduresPage # Doing Science NotesPage # Meiosis NotesPage # Intro to Bio Notes Page # Types of Biology Activity Page # Body System NotesPage # food Journal (3 pages)Page #- Page # Digestion NotesPage # Biomolecules NotesPage # Cardio Vascular NotesPage # Daphnia Lab- Data and proceduresPage # Doing Science NotesPage # Meiosis NotesPage #

Meiosis

The Standards 2a: Meiosis is an early step in sexual reproduction in which the pairs of chromosomes separate and segregate randomly during cell division to produce gametes containing one chromosome of each type. b. Students know only certain cells in a multicellular organism undergo meiosis. 2a: Meiosis is an early step in sexual reproduction in which the pairs of chromosomes separate and segregate randomly during cell division to produce gametes containing one chromosome of each type. b. Students know only certain cells in a multicellular organism undergo meiosis.

Meiosis: Process of cell division that makes gametes (sex cells) 2 cell divisions (Meiosis 1, then Meiosis 2) Makes haploid cells Meiosis: Process of cell division that makes gametes (sex cells) 2 cell divisions (Meiosis 1, then Meiosis 2) Makes haploid cells Human sperm cells Human egg (ovum) cell

Gamete: Sex cells –Male = sperm –Female = ova/egg Fertilization: Union of male and female gametes Zygote: Diploid cell that results from the fusion of two haploid gametes Homologous Chromosomes: chromosomes that are the same size, shape, and carry the same traits. Gamete: Sex cells –Male = sperm –Female = ova/egg Fertilization: Union of male and female gametes Zygote: Diploid cell that results from the fusion of two haploid gametes Homologous Chromosomes: chromosomes that are the same size, shape, and carry the same traits.

Diploid: two identical copies of every chromosome. (ALL somatic (body) cells) – Human diploid # = 46 Haploid: one copy of every chromosome. (ONLY sex cells) – Human haploid # = 23 Diploid: two identical copies of every chromosome. (ALL somatic (body) cells) – Human diploid # = 46 Haploid: one copy of every chromosome. (ONLY sex cells) – Human haploid # = 23 Diploid Haploid

Mitosis starts with 1 diploid cells, then makes 2 identical diploid cells. Meiosis starts with 1 diploid cell, then makes 4 unique haploid cells. Mitosis starts with 1 diploid cells, then makes 2 identical diploid cells. Meiosis starts with 1 diploid cell, then makes 4 unique haploid cells. Between Mitosis and Meiosis:

Prophase 1 – Crossing-over happens. Prophase 1 – Crossing-over happens. Tetrad MomDad synapsis

Crossing over: parts of homologous pairs break off and re-form on the adjacent chromosome Homologous pair in tetrad formation * Notice: chromosomes are aligned so the genes on one match corresponding genes on the other.

Metaphase 1 – homologous pairs line up in the m iddle of the cell Anaphase 1 – homologous pairs split a part from each other Independent assortment happens Metaphase 1 – homologous pairs line up in the m iddle of the cell Anaphase 1 – homologous pairs split a part from each other Independent assortment happens

Independent assortment: Chromosomes separate from each other randomly.

FYI: The more chromosomes, the more ways they can line up…leading to more genetic diversity Humans have 23 sets of chromosomes, so lots of combinations are possible. FYI: The more chromosomes, the more ways they can line up…leading to more genetic diversity Humans have 23 sets of chromosomes, so lots of combinations are possible.

Telophase 1 – We end up with 2 haploid cells. These cells enter Meiosis 2 These cells are not finished yet!!! Time for Meiosis 2!

Looks exactly like mitosis - consists of Prophase 2, Metaphase 2, Anaphase 2, Telophase 2 Occurs in each cell from meiosis 1, this results in four new daughter cells The new cells will develop into sperm or eggs Now you can fill out the major events for meiosis 2 on your chart by looking at the major events in mitosis! Now you can fill out the major events for meiosis 2 on your chart by looking at the major events in mitosis! Looks exactly like mitosis - consists of Prophase 2, Metaphase 2, Anaphase 2, Telophase 2 Occurs in each cell from meiosis 1, this results in four new daughter cells The new cells will develop into sperm or eggs Now you can fill out the major events for meiosis 2 on your chart by looking at the major events in mitosis! Now you can fill out the major events for meiosis 2 on your chart by looking at the major events in mitosis!

Meiosis Overview DNA is doubled Meiosis I: homologous pairs separate Meiosis II: sister chromatids separate 2n n n

Meiosis: 2n  1n Cells divide twice 1 cell  4 cells Happens in sex cells Meiosis: 2n  1n Cells divide twice 1 cell  4 cells Happens in sex cells Mitosis vs. Meiosis Mitosis: 2n  2n Cells divide once 1 cell  2 cells Happens in non-sex cells Mitosis: 2n  2n Cells divide once 1 cell  2 cells Happens in non-sex cells

SummarySummary 1.One major way that meiosis is different from mitosis is… 2.The major events of Prophase 1 are… 3.The major events of Anaphase 1 are… 4.Variation is caused by… 1.One major way that meiosis is different from mitosis is… 2.The major events of Prophase 1 are… 3.The major events of Anaphase 1 are… 4.Variation is caused by…