SU: Vocabulary for cell division (Mitosis) Define each word and then use the word in a complete sentence. Use pp 244-248 Mitosis Cytokinesis Interphase Prophase Metaphase Anaphase Telophase

Chapter 10 Section 2 Chapter 11 Section 4 Cell Division Chapter 10 Section 2 Chapter 11 Section 4

What’s a gene?

Process of Making a Chromosome Nucleosome DNA double helix Coils Supercoils Histones Chromatin – DNA tightly coiled around proteins called Histones Nucleosome – beadlike structure made of chromatin Supercoils – nucleosomes packed together Chromosome – tightly packed supercoils Go to Section:

Chromosomes Function : Made of DNA and Histones (protein) Function : - passes genetic info. from 1 generation to the next Genes- located on chromosomes - information about traits are located here Traits – characteristics passed on by your parents

Chromosomes Numbers Humans = 46 chromosomes Every organism has a specific # of chromosomes Humans = 46 chromosomes The # of chromosomes DOES NOT indicate the COMPLEXITY of an organism Example – a goldfish has 124 chromosomes

Structure of Chromosomes Each chromosome consists of: * CHROMATIDS – identical parts - called “sister chromatids” * CENTROMERE – point at which each chromatid are attached to each other chromatid centromere

Structure of Chromosomes (cont.) When the cell divides into 2 new cells – the “sister chromatids” separate and each one goes into a new cell Each chromosome consists a pair of chromatids (2) Humans = 46 chromosomes = 92 chromatids

Chromosome Quiz Name the 2 substances that make up chromosomes. (2 points) How many chromosomes do humans have? (1 point) What is the function of chromosomes? (1 point) At what point are chromosomes visible in the nucleus? Why? (2 points) Draw and label a chromosome. (4 points)

SU: Meiosis Copy and Answer both questions. You may use your textbook, Section 11-4 What process produces gametes? Mitosis Meiosis Fertilization Chromosome replication Haploid cells are cells that have One chromosome of each type Two chromosomes of each type Pairs of homologous chromosomes Two sets of chromosomes

Classroom Business Meiosis Quiz on Thursday Closed Book Top scorer in each class gets +5 Have your completed Genetics Packet on Thursday! This is worth 50 points. If you do not have one, you will have to spend a lot of time copying the information.

Then each daughter cell prepares to Cell Cycle The series of events that cells go through as they grow and divide. During this cycle the cell: 1. grows 2. prepares for division 3. divides to form 2 “daughter” (identical) cells Then each daughter cell prepares to begin the cycle again

Events of the Cell Cycle includes M phase (Mitosis) Interphase is divided into is divided into G1 phase S phase Prophase G2 phase Metaphase Telophase Anaphase Go to Section:

Interphase Longest phase of the cell cycle Known as the “in-between” period of growth Divided into 3 Phases: G1, S, and G2

G1 (Gap 1) Phase Cells do most of their growing during this phase Cells increase in size Manufacturing of new proteins & organelles

S (Synthesis) Phase DNA is replicated Synthesis of DNA molecules & Histones occur

G2 (Gap 2) Phase Shortest of the phases Organelles & molecules needed for cell division are produced When this phase is complete, cells are ready for the M Phase (mitosis) and begin the process of cell division

Mitosis The 1st stage of cell division in eukaryotic cells Depending on type of cell, this phase can last from a few minutes to several days. Divided into 4 phases

Prophase The 1st & longest phase of Mitosis (50 – 60%of whole process) A. Chromatin condense to form chromosomes B. Centrioles separate and move to opposite sides of the nucleus C. structures called SPINDLES begin to form – they help to separate chromosomes D. Nucleolus disappears & nuclear envelope breaks down

Metaphase Often last only a few minutes Chromosomes line up across the center of the cell Each chromosome is connected to a spindle fiber at its centromere

Anaphase The spindle fibers pull apart the sister chromatids Each chromatid becomes its own chromosome and move towards the centrioles at opposite ends of the cell The phase ends when the chromosomes reach the centrioles & stop moving

Telophase Chromosomes lose their distinct shapes Nuclear envelope re-forms around each group of chromosomes Spindle fibers disappear & a nucleolus becomes visible in each new nucleus Mitosis is complete, but cell division is not

Cytokinesis Cytoplasm pinches in half Each daughter cell has an identical set of chromosomes from the parent cell Usually occurs at the same time as telophase Cell division is not complete until cytokinesis is complete

Overview of Mitosis

SU: Identification of P.M.A.T. Pick up the handout in the front of the room and match the picture to the step in mitosis. These pictures are of cells in the root of an onion plant and the show one of the major phases in cell division. (Interphase, Prophase, Metaphase, Anaphase, or Telophase)

Today’s Assignment Objective: Create a study guide for meiosis. Step 1: Take a clean piece of paper and fold it in half three times so that you have 8 squares. Step 2: Turn to page 276-277 Step 3: Turn the paper horizontal and label each box left to right, top to bottom. Prophase I Metaphase I Anaphase I Telophase I Cytokinesis Prophase II Metaphase II Anaphase II Telophase II Cytokinesis

SU: Meiosis (copy and answer) What is the outcome of meiosis II Four diploid cells Two diploid cells Two haploid cells Four haploid cells All cells that divide by meiosis are Haploid cells Called oogonia Called Spermatogonia Found in reproductive organs

Asexual Reproduction This bud’s for you! Hydra

Human Life Cycle

Homologous chromosomes Karyotype

Cell Cycle Quiz

Label each picture with the correct phase of mitosis D C

Label each picture with the correct phase of mitosis or meiosis. D C

Homologous Chromosomes Chromosomes that are in all sexually reproducing organisms Occur in pairs 2 identical chromosomes = homologous chromosomes same size and shape. are different than all other chromosomes

Diploid Cells Diploid Cells – contain both chromosomes of a homologous pair Human cell = 23 pairs of homologous chromosomes 2 x 23 = 46 Human Chromosome # = 46

Haploid Cells Haploid Cells – contain only 1 chromosome of a homologous pair 23 pairs of homologous chromosomes 1 x 23 = 23 **all egg & sperm cells = 23 chromosomes ALSO KNOWN AS GAMETES (egg)23 + (sperm) 23 = 46 chromosomes – human baby Zygote – a new cell formed by a sperm & egg cell - has the normal number of chromosomes

MEIOSIS The process of reducing the number of chromosomes per cell in half Separating homologous chromosomes in a diploid cell Making a diploid (46) into a haploid (23)

Process of Meiosis Involves 2 distinct divisions: Meiosis I Meiosis II Begin with 1 diploid cell (46) End with 4 haploid cells (23)

Meiosis I Looks like MITOSIS But in Meiosis I, each chromosome is paired with it corresponding HOMOLOGOUS CHROMOSOME This forms a TETRAD – 4 chromatids ( 2 from each chromosome)

Crossing Over TETRAD When homologous chromosomes pair up to make tetrads – they exchange portions of their chromatids This is called CROSSING OVER This results in the exchange of genes between the homologous chromosomes This produces new combinations of genes

RESULTS OF MEIOSIS I The chromosomes go through the same phases as Mitosis Produces 2 new cells with 46 chromosomes each BUT ……………….. 1. the new “daughter” cells DO NOT have identical sets of chromosomes like the parent 2. are different from each - because of crossing over & the separation of the homologous chromosomes

Meiosis II The 2 cells from Meiosis I enter this 2nd division Unlike Meiosis I – the 2 cells ….. do not replicate the chromosomes The cells go through each phase just like in Meiosis I

Results of Meiosis II 4 daughter cells that are haploid cells Have only half of the # of chromosomes All are different from each other All are different from its parent cell

Gamete Formation The making of reproductive cells MALE GAMETE = SPERM CELLS Through meiosis – males produce 4 new sperm cells FEMALE GAMETE = EGG CELLS (OVUM) Through meiosis – females produce only 1 egg cell and 3 polar bodies (incomplete)