Mitosis & Meiosis

Coleman Honors Biology2008-2009

Surface Area: Volume

Surface Area: amount of cell membrane available to transport nutrients and waste.

Volume: the amount of space the internal cell parts take up.

As a cell grows, it’s volume increases faster than its surface area causing two big problems…

1. Too many demands on DNA2. No enough surface area to get nutrients

in and waste out efficiently

Cell Parts

Cell Membrane: protects internal contents of cell; controls flow of materials into and out of cell.

Nucleus: control center of cell; contains DNA

• Nuclear membrane: protects internal contents of nucleus; contains pores which allow information to move in and out of cell

• Nucleolus: site for ribosome production• Chromatin: strands of DNA wound around proteins• Chromosomes: packages of DNA; can only be seen during cell

division; 23 from Mom & 23 from Dad.• DNA: molecule which holds genetic information

Centriole: cell part found in cytoplasm, will help organize cell parts during cell divisionSpindle: microtubules which extend from centriole; will control chromosomes during cell division

Cell Cycle: Overview

Interphase• G1 Phase: cell grows• S-phase: DNA & organelles

replicate• G2 Phase: cell grows

ProphaseMetaphaseAnaphaseTelophaseCytokinesis

M phase

G2 phase

S phase

G1 phase

The Cell CycleSection 10-2

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Drawing Mitosis

Meiosis: The creation of gametes (sex cells) which have half the number of chromosomes than a normal body cell and are all genetically different; created so that sexual reproduction can occur.

Diploid Cell: regular body cell; contains two complete sets of chromosomes (1 set from mom/1 set from dad)

Diploid Number: number of chromosomes (human dipoid # is 46)

Haploid Cell: Cell which contains half the number of chromosomes as a normal body cell

Haploid Number: number of chromosomes in a haploid cell (human haploid # is 23)

Homologous Chromosomes: two chromosomes that carry information about the same traits (1 from mom/1 from dad)

Crossing Over: when homologous chromosomes exchange genetic information.

Tetrad: Paired homologous chromosomes (4 chromatids total)

Section 11-4

Crossing-Over

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Crossing over of tetrad. Occurs during Prophase I of Meiosis. Necessary for genetic diversity of reproductive cells (gametes).

Meiosis I

Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a round of DNA replication, forming duplicate Chromosomes.

Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.

Spindle fibers attach to the chromosomes.

The fibers pull the homologous chromosomes toward the opposite ends of the cell.

Section 11-4

Figure 11-15 Meiosis

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Meiosis II

Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line up in a similar way to the metaphase stage of mitosis.

The sister chromatids separate and move toward opposite ends of the cell.

Meiosis II results in four haploid (N) daughter cells.

Section 11-4

Figure 11-17 Meiosis II

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