Cell Division and Mitosis Chapter 5
Chromosome • Chromosomesare tightly coiled DNA and protein • Chromatinis a mass of DNA and protein • Chromatin coil up to form Chromosomesduring the early stages of cell division • The human chromosome contains about½ billionnucleotides
Structure of the Chromosome • Has 2 identical strands called sister chromatidsthat are connected to the centromere. • Before cell division, chromatidsreplicate 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
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 maleand XY is female.
The Cell Cycle • Cell Cycle is a cycle of growthand division
Three major parts of cell cycle • Interphase • Mitosis – nucleus division • Cytokinesis - celldivision 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. • DNAduplicates • Organelles duplicate • 3 stages of Interphase • G1 phase • Intense growth • Cells spend most of their life in this stage
S phase • DNA duplicates to createsister 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 growthand division of cells. A clump of cells is called a tumor • Factors that may cause cancer: • Mutationin 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 • 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 fibersat the centromere. • Chromosomesline up in the middle of the cell.
Anaphase • Chromatidsseparate. • 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