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.
The cell cycle has two main stages. M: cell division Mitosis: division of the cell’s nucleus Cytokinesis: division of the cell’s cytoplasm Interphase cell growth and normal functions chromosomes duplicate 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. *Mitosis only occurs if the cell is large enough, and if the DNA is undamaged*
Introduction to 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. DNA double helix DNA and histones Chromatin Supercoiled DNA Chromatids Centromere This is a chromosome
Are there different types of chromosomes? Humans and animals have 2 different types. Sex chromosomes: Either X or Y Determine gender Females are XX Males are XY Autosomes: 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?
These copies are called homologous chromosomes. 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?!
In Humans, n = 23 Diploid Haploid Have 2 sets of chromosomes (both chromosomes in a homologous pair) Body cells Have 1 set of chromosomes Sex cells (gametes/sperm and egg cells) In Humans, n = 23
Mitosis
Mitosis 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: 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
This is where the spindle attaches. 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 Meta = middle! 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? The cell cycle is controlled by the cell cycle control system. Cancer cells have severely damaged cell cycle control systems. These cells divide excessively and exhibit bizarre behavior. A lump created from these cancer cells is a malignant tumor. When these cells spread beyond their original site, it’s called metastasis. Cancer What is cancer and how does is relate to mitosis?