The Cell Cycle Mitosis The Cell Cycle The

+ The Cell Cycle & Mitosis

The Cell Cycle The time when a cell divides to form two daughter cells to the time those cells divide again. +

+ n The cell cycle has two main stages. M: cell division n Mitosis: division of the cell’s nucleus n Cytokinesis: division of the cell’s cytoplasm *Mitosis only occurs if the cell is large enough, and if the DNA is undamaged* n Interphase 1. cell growth and normal functions 2. chromosomes duplicate 3. cell is preparing to divide and there is some additional growth Interphase lasts for about 90% of the total time required for the cell cycle.

Review of DNA + What is DNA?

+ DNA… starts off as this… then it coils to this! Into a chromosome

+ DNA wraps around proteins to help condense it. Chromatids DNA double helix DNA and histones Chromati n Supercoiled DNA This is a duplicated chromosome Centromere

+ Are there different types of chromosomes? Humans and animals have 2 different types. 1. Sex chromosomes: n Either X or Y n Determine gender n Females are XX n Males are XY 2. Autosomes: n All other chromosomes in an organism

+ Humans…. . …. have 2 sex chromosomes and 44 autosomes How many total chromosomes are there? How many pairs of chromosomes are there?

Every cell, except sex cells, have 2 copies of each autosome. Where did they come from? These copies are called homologous chromosomes. + • They have the same size and shape. • They carry genes for the same traits. How many pairs of homologous chromosomes do you have in your body cells? !

+ Diploid n Haploid Have 2 sets of chromosomes (both chromosomes in a homologous pair) n Body cells n Have 1 set of chromosomes n Sex cells (gametes/sperm and egg cells) In Humans, n = 23

+ Mitosis

+ Mitosis ² ² ² ALL cells (except sex cells) are made by mitosis Mitosis is a type of cell division where one parent cell divides and forms two genetically identical daughter cells. Mitosis is a form of asexual reproduction.

+ Three important reasons for cell division: 1. 2. 3. Growth = adding more cells to the organism Development = cells become specialized for their function Repair = body heals itself

+ Interphase The cell is preparing to divide. The DNA is duplicated. Parent cell centrioles spindle fibers centrosome nucleus with DNA

+ Prophase The mitotic spindle fibers start to form. The chromatin condenses into chromosomes. The nuclear envelope starts to break down. Each chromosome consists of a pair of sister chromatids that are joined at the centromere. This is where the spindle attaches.

+ Metaphase Duplicated chromosomes line up in the middle of the cell. Meta = middle!

+ Anaphase Sister chromatids separate to opposite sides of the cell.

+ Telophase Two new nuclei form. Chromosomes begin to uncoil. Mitosis ends.

+ Cytokinesis • Cytoplasm divides to create two separate daughter cells • Each new cell has its own nucleus containing identical chromosomes • Each surrounded by its own cell membrane

+ Cancer What is cancer and how does is relate to mitosis? n The cell cycle is controlled by the cell cycle control system. n Cancer cells have severely damaged cell cycle control systems. n These cells divide excessively and exhibit bizarre behavior. n A lump created from these cancer cells is a malignant tumor. n When these cells spread beyond their original site, it’s called metastasis.