Telomers, Telomase, Meiosis and Mitosis – Flashcards
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Has our life span or life expectancy increased?
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Life expectancy only (the point before we start developing fatal illnesses) If we want to increase life span, we have to find a way to rebuild telomeres
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What are telomeres?
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a repeating DNA molecules sequence (for example, TTAGGG) at the end of Eukaryotic chromosomes
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What are the main functions of telomeres?
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Telomeres function by preventing chromosomes from losing base pair sequences at their ends. They also stop chromosomes from fusing to each other.
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How long can telomeres get?
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telomere can reach a length of 15,000 base pairs
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Does telomeres prevent the shortening of DNA molecules?
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No, but they do postpone the erosion of genes near the ends of DNA molecules
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How does a telemere lose its function?
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Each time a cell divides, some of the telomere is lost (usually 25-200 base pairs per division). When the telomere becomes too short, the chromosome reaches a "critical length" and can no longer replicate. This means that a cell becomes "old" and dies by a process called apoptosis.
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What contributes to the shortening of telomeres?
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the shortening of telomeres is connected to aging
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What are Telomerase?
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rebuilds the telomers at the end of our chromosomes so that we don't degrade the end of chromosomes Enzyme that catalyzes the lengthening of telomeres in germ cells.. Also called telomere terminal transferase, is an enzyme made of protein and RNA subunits that elongates chromosomes by adding TTAGGG sequences to the end of existing chromosomes.
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When does telomerase rebuild telomers?
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During embryonic developments and in germ cells
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What is another name for germ cells?
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stem cells-- germ means germative.. can germinate many cells
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What happens if chromosomes of germ cells became shorter in every cell cycle?
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essential genes would eventually be missing from the gametes they produce
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As we age, the stem cells get slower in replacing cells and cell death in the existing cell starts to?
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increase ... for a while the stems cells will keep up with each other but they will eventually slow down
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How does the shortening of telomeres might protect cells from cancerous growth
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limiting the number of cell divisions When a cell becomes cancerous, DNA has been damaged during replication process. If DNA is damaged and we don't see it become cancer, then the next time it divides and the telomeres are all shorten/gone.. it means the cell will die anyways. In this sense, it limits the cancer growth
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If a cell is damaged
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then the probability of cancer is higher. If it divides again and there is no telomere to continue the dna sequence, then the cell will not have a chance to grow into cancer
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What is apoptosis?
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This means that a cell becomes "old" and dies by a process called apoptosis.
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What is cancer cell?
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It is an uncontrolled mitosis-uncontrolled cell division. cells keeps dividing nonstop and in the process, doesn't go through cell differentiation. they stay as embryonic cells.. thy never take on functional shape and do their job
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How does a cell become cancerous?
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DNA has been damaged during replication process, through cancer causing agents, aging process, or something went wrong during the process of cell division
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There is evidence of telomerase activity in cancer cells, which may allow cancer cells to persist .. Explain
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Some cancer cells can actually produce telomerease. Telomerase is the enzyme that rebuilds tolomeres at the end of our chromosomes. If it is a cancer cell and it is constantly getting rebuilt, then that means the cancer cell is immortal = bad!
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What are immortal cells?
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cells that can keep rebuilding telomeres and keep reproducing .. some cancer cells are like this. If they keep reproducing then there will always be more cancer
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Telomerase and immortal cells
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Telomerase is an enzyme made of protein and RNA subunits Function is to elongates chromosomes by adding TTAGGG sequences to the end of existing chromosomes. Telomerase is found in fetal tissues, adult germ cells, and also tumor cells. Telomerase activity is regulated during development and has a very low, almost undetectable activity in somatic (body) cells. Because these somatic cells do not regularly use telomerase, they age. The result of aging cells is an aging body.
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What happens if telomerase is activated in a cell
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the cell will continue to grow and divide. This "immortal cell" theory is important in two areas of research: aging and cancer.
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How to extent a human's life span, expectancy and fountain of youth
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If we can find a way to keep stem cells active and its telemerase
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How does losing telomeres and producing tolemerase bad?
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Losing telomeres signals the end of a cell's life.. contributing to aging process Producing too much telemerase can cause a cell to become cancerous
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Why do we need to replicate DNA? When do we do it?
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We replicate DNA in order to repair and grow in humans, we do two types of cell reproduction 1. growth of the individual 2. for repair of damaged cells 3. production of a new individual/offspring
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3 reasons we do dna replication
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grown, repair and production of offspring
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What is mitosis?
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-Cell division that takes place in somatic cells ( somatic cells are not involved in sexual reproduction. -Results in daughter cells with identical genetic information, DNA
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What reasons has to do with mitosis?
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Growth and repair
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What is meiosis?
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A special type of division produces nonidentical daughter cells (gametes, or sperm and egg cells)
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What type of genetic do we produce in mitosis?
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identical daughter cells
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The asexual reproduction of mitosis occurs where?
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in the somatic of the body
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What are somatic cells?
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general cells .. skin cells. any cells that do not produce egg or sperms is somatic
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Where are somatic cells found?
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heart, lungs, liver, brain, kidneys, etc.
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What reasons has to do with meiosis?
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production of offspring
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What type of reproduction is mitosis?
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Asexual reproduction .. prefix "a" always means without (sex)
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What type of reproduction is meiosis?
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Sexual reproduction
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What type of genetic do we produce in meiosis?
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Different/ non identical daughter cells
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The sexual reproduction of meiosis occurs where?
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in the gamete producing cells. in humans, it happens in ovaries and testies .. eggs and sperms
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What are the gammete producing cells?
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ovaries and testies are gammete producing cells.. meiosis occurs to produce egg cells or sperm cells
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Where are gammete cells produced?
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ovaries and testies.. all infants start out as a female btw.. in them meiosis occurs to produce egg cells or sperm cells
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Our bodies does how many different types of DNA replication
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2 different types 1. copying of the DNA 2. depending on what cell of the body, they will separate differently
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How many chromosomes do somatic cells have?
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have 46 chromosomes, 23 pairs 1 chromosomes from mom, 1 from dad to make a pair - have similar lengths and carry the same genetic information as the pair does
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The 23rd pair is called the sex chromosomes.. it determines
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gender
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When the expression of a chromosome is different, it is called
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recessive and dominant
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How many chromosomes does meiosis have?
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23 chromosomes, no pairs The chromosomes are 1/2 of each pair of the 46 chromosomes .. it is divided in half
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When cell doesn't show chromosomes, it is
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chromatin. it is unwind, not condense. consist of DNA and histone (a packing protein).. chromatin is a thin strand that is barely visible
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When does chromatin condenses?
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when the cell is prepared to do cell division. It condenses into a chromosome
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When DNA is presented as an X, this means
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it is a replicated chromosome
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What is the centromere
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When DNA replication occurs, the two new strands don't immediately replicate. They are held together by centromere, or central unit holding it together.. At this time, it is still considered 1 chromosome
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The DNA replication that is being held together by a centromere/central unit is considered?
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1 chromosome
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What is chromatids
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Each replicated side of a DNA that is being held by centromere .. One replicated chromosome consist of 2 daughter chromatids.. As long as they are attached, they're chromatids
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What is interphase?
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The very beginning when it is prior to cell division, the DNA is scattered throughout the Nucleus as Chromatin. NOT chromosomes
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What happens after interphase?
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it enters meiosis where the chromosomes starts to seprate
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What does mitosis do during this replication?
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It is responsible for pulling the chromosomes apart so that it can become a separate chromosomes, called chromatids. Then the chromatids will become separate chromosomes
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In cell division, Meiosis and Mitosis does what?
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separates the chromosomes
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In unicellular organisms: (Bacteria, Protozoa)
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division of one cell reproduces the entire organism .. can do sexual and asexual. Bacteria always does asexual, but some protozoas can do both
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In Multicellular organisms: (Most fungi, plants and animals)
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division results in the production of gametes (egg & sperm in meiosis) - Growth - Repair for mitosis
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In mitosis, are the 2 daughter cells identical in every aspect?
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no.. only identical in dna
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2 types of cell divisions
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Types of cell division in eukaryotes 1. Mitosis: Cell division that takes place in somatic cells ( somatic cells are not involved in sexual reproduction. -Results in daughter cells with identical genetic information, DNA 2. Meiosis -A special type of division produces nonidentical daughter cells (gametes, or sperm and egg cells)
