Cell Reproduction
Curriculum outcomes to be covered in the unit Compare and contrast the reproduction and development of representative organisms (313) Describe in detail mitosis and meiosis (313-2) Analyze and describe the structure and function of female and male mammalian reproductive systems (313-3) Explain current reproductive technologies for plant and animals (313-5) Evaluate the use of reproductive technologies for humans (313-6)
Before we begin, we must understand that plants and animals grow by mitotic cell division and form gametes (sex cells) by meiosis. We are going to look at both of these processes in length.
Reproduction of the Cell (Humans) The human body is composed of more than one hundred trillion cells. These cells are continually dying and new cells are continually being formed, not to mention the fact that we came from one cell. An identical copy of your hereditary material is found in the nucleus of every somatic cell (does not include reproductive cells)
The hereditary material, also called the genetic blueprint is organized into 46 parts known as chromosomes (DNA molecules are found in chromosomes). Every time a cell reproduces, or divides, each chromosome must be copied and distributed so that each new cell gets a complete and accurate set of information. This process happens in the cell cycle. The making of new cells is called cell division.
The Cell Cycle The cell cycle is a continuous process that does not pause after each cycle Two divisions occur during cell division nuclear division (mitosis) and cytoplasmic division (cytokinesis)
Interphase Interphase is the time interval between nuclear division (not a stage of mitosis) In this stage: Cells grow rapidly Cells make structural proteins that repair damaged parts Cells transport nutrients Eliminate wastes
Prepare for mitosis by building proteins (most important are reactions that control synthesis of DNA ) Genetic material is called chromatin (DNA molecules and proteins in nucleus) Each chromosome (an individual chromosome is a single DNA molecule and its proteins) duplicates itself during interphase
Mitosis A type of cell division where each daughter cell receives the same number of chromosomes as the parent cell. Parent Cell Daughter Cell Daughter Cell
Prophase First phase of mitosis Chromosomes shorten and thicken Original chromosome and its duplicate are attached to each other by a centromere (while attached they are known as sister chromatids)
Centrioles (in cytoplasm, provide attachment for spindle fibers) move to opposite poles of the cell and spindle fibers start to form Centrioles assemble and spindle fibers attach to the centromeres of chromosomes Nuclear membrane start to dissolve
Early Prophase
Late Prophase
Metaphase Second phase of mitosis Chromosomes line up at the equatorial plate. The nuclear membrane completely dissolves. Chromosomes are very dark and attached to spindle fibers
Metaphase
Anaphase The sister chromatids divide and the chromosomes move to the opposite poles of the cell. An identical set of chromosomes move to each pole.
Anaphase
Telophase Chromosomes lengthen again and intertwine The spindle fibers dissolve Nuclear membrane forms around the chromosomes Each new nucleus contains 46 unique chromosomes
Telophase
Cytokinesis After the chromosomes move to opposite ends, the cytoplasm begins to divide Cytokinesis is the division of cytoplasm In animal cells, organelles move to each cell and a furrow develops, pinching off the cell into two daughter cells. This is the end of cell division
Cytokinesis
Draw it
Cell Clock Cells have a biological clock. They can only divide so many times before they die. Not all cells in the body have the same ability to reproduce. Age is one reason why cells stop dividing.
Cells such as skin cells reproduce more often than muscle cells, nerve cells and secretory cells. Two types of human body cells can divide continuously: sperm-producing cells (spermatocytes) and cells of a cancerous tumor.
Readings Biology 11 P. 82-90 Questions P. 90 #2, #3, #4, #10