Cell Division

Words to Know Gamete – The male or female reproductive cell that contains half of the DNA – sex cell Egg Cell – The Ovum; the female reproductive cell (gamete); usually not mobile Sperm Cell– The male reproductive cell (gamete) ; usually mobile

Words to Know Parent Cell – The old product being divided or used Daughter Cell – The new product(s) being formed or used Sisters – Identical products that are joined

Words to Know Diploid – Meaning the cell has two sets of chromosomes = full set of chromosomes - In humans it would be 46 chromosomes Haploid – Meaning the cell has one set of chromosomes = half the chromosomes - Gamete cells -In humans it would be 23 chromosomes

Why do cells divide? Grow Reproduce Repair

Cell Reproduction All organisms REPRODUCE. Why? This allows for growth, development and the survival of the species

There are 2 types of reproduction Asexual Reproduction Requires A single parent!!! Results in the offspring having the same hereditary material (DNA)

Asexual Reproduction (cont)… In other words, the new cells are an exact copy of its parent (allow for little variation among species)

Types of Asexual Reproduction Fission – cell splits in half (ex: Amoeba)

Types of Asexual Reproduction (cont)… Budding – a new organism grows off from the side of an adult (ex: Hydra)

Types of Asexual Reproduction (cont)… Regeneration – a new organism grows from a severed body part (ex: starfish)

MITOSIS

Mitosis The process of cell division which results in the production of two daughter cells from a single parent cell. The daughter cells are identical to one another and to the original parent cell.

Mitosis Mitosis is the method used for cell division and reproduction in asexual organisms Mitosis is associated with growth and repair in sexually reproducing organisms. .

Mitosis can be divided into stages A preparation stage – Interphase The four main MITOTIC STAGES Prophase – Metaphase Anaphase – Telophase The separation stage - Cytokinesis

Interphase – Preparation Step The cell prepares for the main four division phases Plant Cell DNA replicated Organelles replicated Cell increases in size Animal Cell DNA replicated Organelles replicated Cell increases in size

Interphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Prophase – 1st Mitotic Stage Animal Cell Chromatin condense to form chromosomes as chromatids joined by a centromere Centrioles move to opposite ends of the cell Nuclear membrane dissolves. Plant cell Chromatin condense to form chromosomes as chromatids joined by a centromere Centrioles move to opposite ends of the cell Nuclear membrane dissolves.

Prophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Metaphase – 2nd Mitotic Stage Animal Cell Spindle fibers align chromosomes at the center of the cell Plant Cell Spindle fibers align chromosomes at the center of the cell

Metaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Anaphase – 3rd Mitotic Stage The paired chromosomes divide Animal Cell Spindle fibers pull chromosomes apart ½ of each chromosome (called chromotid) moves to opposite sides of the cell Plant Cell Spindle fibers pull chromosomes apart ½ of each chromosome (called chromotid) moves to opposite sides of the cell

Anaphase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Telophase – 4th Mitotic Stage Partitioning of the cell begins Plant Cell 2 nuclei form Cell membrane starts to pinch in to form the 2 new daughter cells Spindle fibers disappear Animal Cell 2 nuclei form Cell membrane starts to pinch in to form the 2 new daughter cells Spindle fibers disappear

Telophase Plant Cell Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

What happens to a cell after Mitosis is complete? Cytokinesis Cell splits into two identical daughter cells with complete set of organelles Animal – nuclear membrane develops and cells pinch apart Plants – Cell wall forms between two new cells and nuclear membrane develops.

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                              Cytokinesis                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                              Cytokinesis                                                             

How did you get here? Sexual Reproduction Reproduction in which two (2) parents are involved Sex cells are called gametes (egg and sperm cells are gametes)

What is sexual reproduction? starts with the formation of gametes and ends when one gamete joins another gamete. The joining of egg and sperm is called fertilization, resulting in the production of a zygote zygote

How are gametes produced? Meiosis A process whose purpose is to reduce the chromosome number in the cells Produces 4 new cells with half the number of chromosomes as the parent - haploid

Meiosis – two divisions of the nucleus 46 Parent Cell 1st Division 46 46 2nd Division – 4 new daughter cells with ½ the # of chromosomes 23 23 23 23

Meiosis continued Diploid Cells: have two of every chromosome (body cells) Haploid Cells: have just one chromosome from each pair (gametes)

MEIOSIS

One parent cell produces four daughter cells. Meiosis Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced. One parent cell produces four daughter cells. Daughter cells have half the number of chromosomes found in the original parent cell

During meiosis, DNA replicates once, but the nucleus divides twice.

Four stages can be described for each division of the nucleus. Meiosis Four stages can be described for each division of the nucleus.

First division of meiosis Meiosis I First division of meiosis

First Division of Meiosis Prophase 1: Each chromosome duplicates and remains closely associated. These are called sister chromatids. Metaphase 1: Chromosomes align at the center of the cell. Anaphase 1: Chromosome pairs separate with sister chromatids remaining together. Telophase 1: Two daughter cells are formed with each daughter containing only one chromosome of the chromosome pair.

Prophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Prophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Metaphase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Telophase I http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Second Division of Meiosis

Second Division of Meiosis Prophase 2: DNA does not replicate. Metaphase 2: Chromosomes line up at the center of the cell Anaphase 2: Centromeres divide and sister chromatids move separately to each pole. Telophase 2: Cell division is complete. Four haploid daughter cells are formed.

Prophase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Metaphase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Telophase II http://everyschool.org/u/logan/cellreproductionx/rogersa/research/meiosis.html

Meiosis http://www.biosci.uga.edu/almanac/bio_103/notes/apr_3.html.

Differences in Mitosis & Meiosis Asexual Cell divides once Two diploid daughter cells Genetic information is identical Meiosis Sexual Cell divides twice Four haploid daughter cells Genetic information is different