Asexual Reproduction The Cell Cycle 1

DNA Replication DNA must be copied or replicated before cell division Each new cell will then have an identical copy of the DNA Original DNA strand Two new, identical DNA strands

Identical Daughter Cells Two identical daughter cells Parent Cell

Chromosomes

Prokaryotic Chromosome The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes or 23 identical pairs

Eukaryotic Chromosomes Each chromosome is composed of a single, tightly coiled DNA molecule Chromosomes can’t be seen when cells aren’t dividing and are called chromatin

Chromosomes in Dividing Cells Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids

Karyotype A picture of the chromosomes from a human cell arranged in pairs by size First 22 pairs are called autosomes Last pair are the sex chromosomes XX female or XY male

The Y Chromosome Decides Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome

Cell Division in Prokaryotes

Cell Division in Prokaryotes Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission Single chromosome makes a copy of itself Cell wall forms between the chromosomes dividing the cell Parent cell Chromosome relicates Cell splits 2 identical daughter cells

Prokaryotic Cell Undergoing Binary Fission

How do little elephants grow up to be BIG elephants?

Why do animals shed their skin?

The process of asexual reproduction in eukaryotes begins after a sperm fertilizes an egg.

Three reasons why cells reproduce by asexual reproduction: 1. Growth 2 Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Cancer develops when cells that reproduce by asexual reproduction divide out of control.

The Cell Cycle

Sketch the Cell Cycle DNA Copied Cells prepare Cells Mature for Division Cells Mature Daughter Cells Cytoplasmic Division Nuclear Division Cell Divides into 2 Identical cells

Animated Cell Cycle Interphase Prophase Metaphase Anaphase http://www.cellsalive.com/mitosis.htm Interphase Prophase Metaphase Anaphase Telophase & Cytokinesis

Interphase occurs before mitosis begins Chromosomes are copied (# doubles) Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosomes) change to sister chromatids at end of this phase

Interphase - G1 Stage 1st growth stage after cell division Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities Cells can leave this phase (G0)and go through a rest phase and then reenter before proceeding to the S phase

Interphase – S Phase Synthesis Phase DNA is copied or replicated Two identical copies of DNA Original DNA

Interphase – G2 Stage 2nd Growth Stage Occurs after DNA has been copied All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized

What’s Happening in Interphase? What the cell looks like Animal Cell What’s occurring

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

Mitosis

Mitosis Division of the nucleus Only occurs in eukaryotes Has four stages Doesn’t occur in some cells such as brain cells

Four Mitotic Stages Prophase Metaphase Anaphase Telophase

Prophase Mitosis begins (cell begins to divide) Centrioles (or poles) appear and begin to move to opposite end of the cell (animal cells only). Spindle fibers form between the poles. Nucleus and nucleolus disappear Chromatin condenses (coils) to form chromosomes

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

Metaphase Chromosomes are now lined up at the equator Chromatids (or pairs of chromosomes) attach to the spindle fibers. Chromosomes are now lined up at the equator

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

Anaphase Occurs rapidly Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.

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

Telophase Two new nuclei and nucleoli form. Chromosomes appear as chromatin (threads rather than rods). Cleavage furrow begins to forms in animal cells and a cell plate begins to form in plant cells Mitosis ends.

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

Cytokinesis occurs after mitosis Cell membrane moves inward to divide the cytoplasm and create two daughter cells – each with its own nucleus with identical chromosomes.

Animal Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Plant Mitosis -- Review Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

IPMATC REMEMBER! Interphase Prophase Metaphase Anaphase Telophase Cytokinesis IPMATC A mnemonic to help remember the stages of mitosis. I Pray More At The Church

Cell Cycle

- Cell Division The Cell Cycle 43

Mitosis Animation http://www.cellsalive.com/mitosis.htm