Chapter 10

 Does an animal get larger because each cell increases in size or because it produces more of them?  In most cases, living things grow by producing more cells  Identify the problems caused by growth of cells

 Chromosomes are made of DNA (genetic information) and proteins (histones)  The cells of every organism have a specific number of chromosomes ◦ Fruit flies = 8, human = 46, carrots = 18  Chromosomes are not visible in most cells except during cell division  Each chromosome consists of two identical sister chromatids which separate during cell division  Each pair of chromatids is attached in an area called the centromere

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 The larger a cell becomes, the more demands a cell places on its DNA ◦ If extra copies of DNA are not made, an “information crisis” would occur  The cell also has more trouble moving nutrients and wastes across the cell membrane ◦ Food, oxygen, water, and wastes move through the cell membrane

 Each cell has only one set of genetic information ◦ must be copied before cell division begins  The first stage, division of the cell nucleus, is called mitosis  The second stage, division of the cytoplasm, is called cytokinesis  Reproduction by mitosis is classified as asexual

 Interphase is the period in between periods of cell division  The cell cycle is the series of events that cells go through as they grow and divide  During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cycle again  The cell cycle consists of four phases ◦ M, S, G 1, and G 2

Mitosis

 Cytokinesis is the division of the cytoplasm itself and usually occurs at the same time as telophase  In most animal cells, the cytoplasm is drawn inward until the cytoplasm is pinched into two nearly equal parts  In plants, a structure known as the cell plate forms midway between the divided nuclei

 Not all cells move through the cell cycle at the same rate  The cells of the skin, digestive tract, and bone marrow grow and divide rapidly throughout life  How is the cell cycle regulated?  How are cancer cells different from other cells?

 Proteins called cyclins - seemed to regulate the cell cycle  Proteins that respond to events inside the cell are called internal regulators  External regulators respond to events outside of the cell

 Cancer is a disorder in which some of the body’s own cells lose the ability to control growth  They divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues  Causes include smoking, radiation, and viral infections