AiS Challenge Team Interim


Team Number: Team 019

School Name: Bloomfield High School

Area of Science: Biology

Project Title: Aging



Aging is the process of growing old or maturing. There are many aging theories, but most of them reduce down to two categories: Programmed aging and Wear and Tear aging. Programmed aging is genetically programmed. Inside the body, the organisms force elderliness and deterioration. They are intended by nature to age. Wear and Tear is based on environmental factors. Aging is not genetically programmed. We are researching on the Programmed aging, and we will focus on the Telomeric Theory of Aging. In our research, we have learned that a human stem cell has 23 chromosomes pairs. Each chromosome has two ends, giving 92 chromosome ends in each cell. At each end of a chromosome is a cap called a telomere. Telomeres consist of the six-base repeating sequence TTAGGG (2 Thymines, 2 Adenine and 3 Guanines). A portion of every telomere is lost whenever a cell is divided; therefore, the telomere shortens gradually. Leonard Hayflick did one of the most famous experiments in gerontology. He observed that embryonic fibroblasts (connective tissue cells) in tissue culture would divide about 50 times before they quit dividing. This 50-division limit (the Hayflick Limit) seemed to be a property of the cell nucleus or DNA. Therefore, if an old nucleus is transplanted to a young cell, the nucleus still divides no more than 50 times. Similarly if a young nucleus is transplanted to an old cell, the nucleus still divides only 50 times. Also in our research we found the length of the remaining telomere is a good sign of how many divisions a dividing cell has left. Once the telomere is gone, functional genetic DNA is lost with each cell division and the cells are soon missing essential proteins. Germ cells, stem cells and cancer cells contain an enzyme called telomerase that replaces lost telomeres, thus preventing them from experiencing a Hayflick Limit. Hydrocortisone, a steroid hormone, C21H30O5, produced by the adrenal cortex, that regulates carbohydrate metabolism and maintains blood pressure, also can increase the Hayflick Limit, but at the cost of increased mutation. At conception each human telomere is about 10,000 base pairs long (i.e. about1, 666 TTAGGG repeats), and the typical chromosome is about 13 thousand times longer (130 million base-pairs). Nine months later, at birth, the average telomere is half as long as it was at conception. Telomeres lose an average of eight TTAGGG subunits per cell division, so half of the telomere length was lost due to the cell divisions of embryonic development. If cells continue to divide after having lost their telomeres (i.e. beyond the Hayflick Limit of about 50 cell divisions), they not only malfunction due to lost genes, but the chromosomes ends start sticking to other chromosomes, increasing the number of abnormalities. Typically a cell will invoke apoptosis (cell suicide) mechanisms, which prevent the cell from dividing or becoming cancerous. The Hayflick Limit itself may be a means of preventing cancer. Diseases that resemble the telomere abnormalities include: Hutchinson-Gilford syndrome (childhood progeria), and Downs syndrome. Our research states in Hutchinson-Gilford syndrome (childhood progeria), a child is born with abnormally short telomeres. Childhood progeria occurs once in every 8 million births. At age five the telomeres are about as long as those of a very elderly person. In Downs syndrome the telomeres of the immune system cells shorten at an abnormally high rate. An extra copy of chromosome twenty-one causes Downs syndrome. Chromosome twenty-one is the shortest human chromosome (50 million base-pairs). Victims of this disease are vulnerable to infection, due to the rapid shortening of the telomeres of their leukocytes (white blood cells). We will further research the Telomeric Theory of Aging. We are in the process of making a mathematical model of telomere cells dividing. We will go deeper into our research and figure out if extending the telomeres length could rejuvenate the cell. If we can rejuvenate the cell then maybe aging could be controlled or possibly prevented. We will work hard to find an answer.

Telomeric Theory of Aging

San Juan College Genl Reference Ctr Gold Science News End Games: Tips of Chromosomes May Contain Secrets of Cancer and Aging (telomeres) http://web5.infotrac.g/purl=rcl_GRGM_0_A17949272&dyn=3!ar_fmt?sw_aep=nm_a_sjcol

Telomere Synthesis and Function

Mechanisms of Aging

The Evolution of Aging

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