Mitosis and DNA Replication

Cell Division Occurs in humans and other organisms at different times in their life. Cell Division differs depending on type of organism: Eukaryotic organisms undergoing growth, development, repair, or asexual reproduction divide by mitosis. EXAMPLE: new hair, nails, skin, liver, cells, etc… are produced.

Interphase 95% of cell cycle in interphase Cells replicate their DNA

Mitosis Mechanism used by cells to replicate DNA and produce identical cell copies. 5% of cell cycle is mitosis Happens in all cells

Mitosis It is broken down into 5 major stages: Prophase Metaphase Anaphase Telophase

Prophase 1st phase of Mitosis Nucleolus breaks down & Nuclear membrane disappears Chromosomes condense –sister chromatids stay attached by the centromere Kinetochore fibers form

Metaphase 2nd phase of Mitosis The kinetochore fibers move the Chromosomes to the equator (middle) Each chromatid is attached to the fibers at the centromere.

Anaphase 3rd phase of Mitosis Centromeres split Sister chromatids are pulled apart to opposite poles of the cell After chromatids separate, they are considered to be individual chromosomes.

Telophase 4th phase of Mitosis Chromosomes begin to uncoil back into chromatin state. Cytokinesis Cytoplasm divides Two new daughter cells are now separate 2 nuclear membranes form around each set of chromosomes. Nucleolus forms in each of the newly formed cells.

Mitosis Animation

Deoxyribose Nucleic Acid DNA double-stranded sugar = deoxyribose bases = A,T,C,G

Free Nucleotide

DNA Replication

DNA Replication DNA copies itself exactly (Occurs within the nucleus) Any mistake in copying = mutation

Basic Facts of DNA Replication Complementary base pairing makes replication possible C - G A - T

Basic Facts of DNA Replication One side of DNA molecule is a template for making the other side (strand)

DNA Replication Step 1: Uncoil & unzip DNA molecule This occurs because of a weak hydrogen bond between the bases.

DNA Replication Step 2: Enzyme brings in complementary N-bases

DNA Replication Each new DNA molecule contains one old strand & one new strand

DNA Replication Animation