Cell Division and Mitosis Chapter 6

Chromosome Chromosomes are tightly coiled DNA and protein Chromatin is a mass of DNA and protein Chromatin coil up to form Chromosomes during the early stages of cell division The human chromosome contains about ½ billion nucleotides

Structure of the Chromosome Has 2 identical strands called sister chromatids that are connected to the centromere. Before cell division, chromosomes replicate to make the sister chromatid. The shape of the chromosome is a double helix.

Chromosome number In humans there are: 46 in normal cell 23 in sex cells The set of chromosomes for an organism is called a karyotype Diploid - 2 sets of chromosomes (pair), one from each parent Haploid - 1 chromosome

Diploid Haploid 23 8 66 46 4 33

Sex Chromosomes Sex chromosomes determine whether you are male or female X and Y In humans: XX is female and XY is male. the female egg can only contain a X chromosome. the male sperm contains either a X or Y chromosome. The male determines the sex of the child In birds, moths, and butterflies: XX is male and XY is female.

The Cell Cycle Cell Cycle is a cycle of growth and division

Three major parts of cell cycle Interphase Mitosis – nucleus division Cytokinesis - cell division For all eukaryote cells the stages are the same, but the length of time the stages last varies.

Interphase Cells carry out the tasks of life. DNA duplicates G1 phase Organelles duplicate 3 stages of Interphase G1 phase Intense growth Cells spend most of their life in this stage

DNA duplicates to create sister chromatids S phase DNA duplicates to create sister chromatids G2 phase Growth Organelles duplicate Cell prepares for division

Mitosis 4 stages Prophase Metaphase Anaphase Telophase

Cytokinesis Cellular division Cell divides in half and becomes 2 identical daughter cells

Controlling the cell cycle The cell cycle is controlled by proteins called cyclins. Cancer is the uncontrolled growth and division of cells. A clump of cells is called a tumor Factors that may cause cancer: Mutation in genes Radiation Cigarette smoke Diet and obesity

Cell Division Cell division in Prokaryote cells (bacteria) Bacteria grows Circular DNA copies itself and attaches to the cell membrane Cell pinches inward and splits This is called binary fission

Mitosis 4 distinct phases Process in which the nucleus divides to form two identical nuclei Occurs after interphase 4 distinct phases “PMAT” to help remember 4 steps of Mitosis

Prophase Chromatin finish condensing and coil up to form chromosome. Nuclear membrane disappears Spindle fibers begin to stretch across the cell

metaphase chromosomes attach to spindle fibers at the centromere. Chromosomes line up in the middle of the cell.

Anaphase Chromatids separate. Spindle fibers start to break down. Chromatids are pulled the opposite sides by the spindle fibers. Spindle fibers start to break down.

Telophase Nuclear membrane reappears around each set of chromosomes. Chromosomes uncoil and form chromatin. Spindle fibers disappear.

Cytokinesis Cytoplasm is pinched in half and separates. Forms two identical daughter cells.

Results of Mitosis 1. Each cell in your body (except sex cells) has the same number of chromosomes- 46

Results of Mitosis Allows for growth and replaces worn out or damaged cells

D. Asexual Reproduction A new organism is produced from one parent organism 3 types Fission Budding Regeneration

D. Asexual Reproduction 1. Fission- An organism with no nucleus divides into two identical organisms by fission Example: bacteria

D. Asexual Reproduction 2. Budding- A small exact copy of the adult grows from the body of the parent Example: hydra

D. Asexual Reproduction 3. Regeneration, a whole new organism grows from a piece of the parent Example: sea star