Heredity Concept 1: Meiosis. Agenda for 10/28/2013. Wake up work #1 Get new packets! Concept 1 Notes p. 2-5 Draw the steps of Meiosis 1 and Meiosis II. Wake Up Work #1. What are the stages of Cell Division/Mitosis? I______________ P_____________ M_____________ A_____________
Recall learning about mitosis during the Cells Unit:
Do you want your child to be an aquatic rat?
Each parent only passes on HALF of their chromosomes (23) – one from each pair – so the offspring ends up with a full set (46).
Meiosis I: Reduction from haploid to diploid
Meiosis II : Separation of sister chromatids. Haploid daughter cells from Meiosis I divide.
Results in four haploid daughter cells called gametes, or sex cells (egg and sperm) with undoubled chromosomes
Nuclear membrane breaks down
Centrioles separate and make spindle fibers
Homologous chromosomes pair up
Exchange of genetic material between pairs occurs in a process called crossing over.
Homologous Chromosomes line up in the middle of the cell in pairs (double row).
The chromosome pairs separate.
Homologous chromosomes move to opposite ends of the cell.
Sister chromatids remain attached.
Chromosomes gather at the poles
Nuclear membrane forms & the cytoplasm divides (this is called cytokinesis)
End result:2 daughter cells that have a unique combination of 23 duplicated chromosomes from both parents
The nuclear membrane breaks down.
Spindle fibers form in each of the daughter cells & attach to the centromeres of the sister chromatids.
Chromosomes line up across the middle of the cell (equator)
The sister chromatids are pulled apart from each other & move to opposite sides of the cell.
Nuclear membrane forms in each cell and cytoplasm divides
End Result: Four, genetically unique, haploid daughter cells. Each contains one set of chromosomes