WARM UP #3 1/26 1.What is happening in the picture? 2.How many chromosomes is this cell starting with? 3.How many chromosomes in each cell is it ending with? 4.How many cells are made in the end? 5.Name any PHASES you remember

TODAY 1/26 1.Video comparing mitosis to meiosis – sheet 2.Finish notes #2 from yesterday 3.Practice sheet SAME LEARNING TARGET I can describe and identify the steps of cell division and compare mitosis and meiosis.

MITOSIS – review of what we saw yesterday MEIOSIS comparing 2ztU&feature=related

CHAPTER 11 NOTES #2 MITOSIS and MEIOSIS

MITOSIS In SOMATIC CELLS only - body cells (skin, muscle, bone, etc) 1 cell divides to make ______ cells End with __________ # of chromos = DIPLOID EX: start with 46, end with _____ * STEPS: _________________________ MEIOSIS In GAMETES only – sex cells (eggs and sperm) 1 cell divides to make _____ cells End with __________ # of chromos = HAPLOID EX: start with 46, end with _____ * STEPS: __________________________ 2 WAYS THAT CELLS DIVIDE

Why need meiosis?

MAIN PHASES of MITOSIS and MEIOSIS: INTERPHASE - when the cell is not dividing (resting) Chromosomes seen as single strands

1. PROPHASE Chromosomes doubled – look like X’s

2. METAPHASE Chromosomes line up in middle

METAPHASE – MEIOSIS Instead of lining up single file, they line up in pairs of 2 (homologous pairs) CROSSING OVER CAN HAPPEN Mixes up genes for more variation

3. ANAPHASE Chromosomes are pulled apart

4) TELOPHASE Cell splits into two

MEIOSIS – goes through phases again END 4 cells with ½ the # of chromos.

REVIEW: WHAT PHASE?

MITOSIS AS SEEN IN OUR CELLS

PRACTICE ASSIGNMENT Use your notes and diagram to answer the questions, if not complete today, then it becomes homework.

MITOSIS RATES DO all cells go through mitosis at same rate? NO EX: stomach cells fast, liver cells slow AGING – mitosis slows down - cells don’t repair or replace as fast CANCER – mitosis speeds up of abnormal cells

CELL CYCLE The time the cells spend in each phase