Mitosis is a part of the cell cycle in which chromosomes in a cell nucleus are separated into two identical sets of chromosomes, each in its own nucleus. In general, mitosis (division of the nucleus) is often followed by cytokinesis, which divides the cytoplasm, organelles and cell membrane into two new cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of an animal cell cycle—the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell.

The process of mitosis is divided into stages corresponding to the completion of one set of activities and the start of the next. These stages are prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have already duplicated, condense and attach to fibers that pull one copy of each chromosome to opposite sides of the cell. The result is two genetically identical daughter nuclei. The cell may then divide by cytokinesis to produce two daughter cells. Producing three or more daughter cells instead of normal two is a mitotic error called tripolar mitosis or multipolar mitosis (direct cell triplication / multiplication). Other errors during mitosis can induce apoptosis (programmed cell death) or cause mutations. Certain types of cancer can arise from such mutations.

Mitosis occurs only in eukaryotic cells and the process varies in different organisms. For example, animals undergo an "open" mitosis, where the nuclear envelope breaks down before the chromosomes separate, while fungi undergo a "closed" mitosis, where chromosomes divide within an intact cell nucleus.[6] Furthermore, most animal cells undergo a shape change, known as mitotic cell rounding, to adopt a near spherical morphology at the start of mitosis. Prokaryotic cells, which lack a nucleus, divide by a different process called binary fission.

Errors can occur during mitosis, especially during early embryonic development in humans. Mitotic errors can create aneuploid cells that have too few or too many of one or more chromosomes, a condition associated with cancer. Early human embryos, cancer cells, infected or intoxicated cells can also suffer from pathological division into three or more daughter cells (tripolar or multipolar mitosis), resulting in severe errors in their chromosomal complements.

In nondisjunction, sister chromatids fail to separate during anaphase. One daughter cell receives both sister chromatids from the nondisjoining chromosome and the other cell receives none. As a result, the former cell gets three copies of the chromosome, a condition known as trisomy, and the latter will have only one copy, a condition known as monosomy. On occasion, when cells experience nondisjunction, they fail to complete cytokinesis and retain both nuclei in one cell, resulting in binucleated cells.

Anaphase lag occurs when the movement of one chromatid is impeded during anaphase.[50] This may be caused by a failure of the mitotic spindle to properly attach to the chromosome. The lagging chromatid is excluded from both nuclei and is lost. Therefore, one of the daughter cells will be monosomic for that chromosome.

Endoreduplication (or endoreplication) occurs when chromosomes duplicate but the cell does not subsequently divide. This results in polyploid cells or, if the chromosomes duplicates repeatedly, polytene chromosomes. Endoreduplication is found in many species and appears to be a normal part of development. Endomitosis is a variant of endoreduplication in which cells replicate their chromosomes during S phase and enter, but prematurely terminate, mitosis. Instead of being divided into two new daughter nuclei, the replicated chromosomes are retained within the original nucleus. The cells then re-enter G1 and S phase and replicate their chromosomes again. This may occur multiple times, increasing the chromosome number with each round of replication and endomitosis. Platelet-producing megakaryocytes go through endomitosis during cell differentiation.

Nutrition

Autotrophic Nutrition

The term autotroph has been derived from two Greek wards-auto means self and troph means nutrition. In this mode of nutrition, the organisms prepare their own food from simple raw materials like water, carbon dioxide and mineral salts in the presence of sunlight. Chlorophylls present in the chloroplast or green plants are the site of food production. Accordingly all green plants are the examples of this category. The process by which they synthesize food is known as photosynthesis. Some nongreen becteria like sulphur bacteria can use energy which they derive from some chemical reactions occurring in them. With this energy they manufacture their food. This process is called chemosynthesis. Thus the autotrophs include both the photosynthetic and che4mosynthetic organisms.

Heterotrophic Nutrition

The word heterotrophy has been derived from two Greek words-hetero means different and troph refers to nutrition of food. The organisms which derive their food from others are known as heterotrophic organisms. They depend for their food on other organisms, hence they are called consumers. All animals, human beings and non-green plans like fungi come under this category. They consume complex organic food prepared by autotrophs or producers and break it into simple from to derive nourishment. Thus the difference between heterotrophy and autotrophs is basically in the mode of production of food. Due to lack of chlorophyll, heterotrophs cannot synthesize their food while autotrophs can perform photosynthesis.

Heterotrophs may be parasitic, saprophytic and holozoic.

1. Parasitic:

The term has been derived from two Greek works: Para means feeding and sites means grains. Parasitic organisms are those which live on or inside other living organisms to derive their food. Such a mode of nutrition is known as parasitic nutrition. A parasite derives its food (nutrition) from the host in different ways the mode of feeding depends upon its habit, habitat, and modifications. An ectoparasite, which lives on the outer surface of the host, may have certain devices to obtain blood from the host. A mosquito gets a blood meal by inserting its mouth parts into the skin, but a leech has rasping jaws which

lacerate the skin of cattle and man. The blood which oozes out is sucked by the leech. A hook-work living in the intestine of man sucks the digested food of the host through its mouth. But a tapeworm which lives in the intestine of man does not even have a mouth of its own. Neither does it have an alimentary canal. A tape-worm thus obtains nutrition through its body surface. An intracellular parasite such as Plasmadium lives on the protoplasm of the cell it has invaded, viruses, fungi and some non-green plants have parasitic mode of nutrition.

In plants, the fungus puccinia is a parasite on wheat and barberry plants; Cuscuta or dodder plant (amar bel) is a parasite on many plants and obtains food from them. Parasites often lack well-developed organ systems but their body parts are modified for attachment to the host or for sucking food from the host’s body.

2. Saprophytic:

The word saprophyte has been derived from the Greek words sapro meaning rotten and phyto meaning plants. Saprophytic organisms derive their food from decomposing dead organisms. The complex organic compounds become simpler in dead organisms when the decomposition sets in. they feed on substances which were once part of living organisms such as stored food, wood, leather and rotten plant products. The common examples of saprophtyes are fungi (moulds, mushrooms, yeasts) and many bacteria. Saprophytes secrete enzymes which are released on he substrate (i.e., the place on which they grow). These enzymes digest and break down the complex food material like starch into simpler ones. The soluble end product like sugar is then absorbed back by the saprophyte. This is called extracellular digestion. The saprophytic mode of nutrition can best be shown by the common bread mould, Rhizopus mucor (pin mould), Neurospora (pink bread mould), Morchella (sponge fungus) and Agaricus (mushrrom) also represent similar mode3 of nutrition

3. Holozoic

The word holozoic has been derived from Greek words: holos means whole and zoon means animal. Holozoic nutrition involves ingestion of complex organic substances. The food of most animals contains large organic substances. In this mode, small or large particles of food are consumed through an opening called mouth (Ingestion). Then these are hydrolyzed into simpler and soluble forms (digestion). Simplified products are absorbed into the body and the undigested product is removed from the body (Egestion).

4. Photosynthesis

Plants are autotrophs; the only nutrients they require are carbon dioxide from the air, and water and minerals from the soil. Specifically, plants are photoautotrophs, organisms that use light as a source of energy to synthesize lipids, proteins, and other organic substances. Photosynthesis also occurs in algae, including certain protists, and in some prokaryotes

Balanced diet

A balanced diet is one that gives your body the nutrition it needs to function properly. In order to get truly balanced nutrition, you should obtain the majority of your daily calories from fresh fruits and vegetables, whole grains, and lean proteins.

Factors that affect the daily energy requirements

Physical Activity

Work out longer or harder than normal and you’ll naturally burn more calories. A 185-pound bicyclist, for example, burns 378 more calories in a half-hour if he covers 10 miles instead of his normal six to seven, yet men tend not to increase caloric intake commensurately, creating an energy deficit. Women, however, consume nearly the same number of calories they expend after engaging in high-intensity exercise. Nutritionists occasionally encounter both male and female clients for whom physical activity increases appetite. Depending upon intensity and duration, you experience after-burn -- the burning of calories at an increased rate -- for 15 minutes to 48 hours after exercise. After 80 minutes of high-intensity bicycling, for example, you burn an additional 130 calories; 80 minutes of low-intensity cycling burns about one-third of that.

Energy Density

Barbara Rolls, Ph.D. and co-author of “Volumetrics,” cites a trio of studies and one survey establishing that you generally eat the same amount of food by weight each day, even though your daily caloric intake can change considerably. The change occurs because some foods, like tomatoes, strawberries, skim milk and vegetable soup, have relatively few calories for their weight, or low-energy density. Others, like bacon, chocolate chip cookies, peanut butter and potato chips, have relatively little weight for their calories, or high-energy density. Rolls explains that by eating more of the former foods and fewer of the latter you can feel “full and satisfied” on fewer calories. She notes a Penn State study in which female subjects told to eat as much as they want during a series of typical meals consumed about 400 fewer calories on days the meals contained more low-energy-density foods.

Beverages

While drinking water with your meal will not cause you to consume fewer calories, you affect your daily caloric count with the other beverages you drink -- or don’t drink. A review of 30 studies published in

the “American Journal of Clinical Nutrition,” for instance, found a correlation between drinking sugar-sweetened beverages -- soda, coffee, iced tea, fruit drinks, energy drinks, sports drinks, etc. -- and consuming more calories than needed. Research performed at Purdue University and published in the “International Journal of Obesity” in 2000 determined a reason for this besides the sugar in the drinks. After consuming an excess of solid carbohydrates, subjects naturally reduced caloric consumption later, something they did not do when the excess of carbohydrates came in liquid form. Because liquid carbs don't "register" in your body, the Harvard School of Public Health suggests reducing or eliminating consumption of sugar-sweetened beverages to help control your weight.

Other Considerations

Research presented at a 2012 American Heart Association conference found that subjects who slept two-thirds of their typical amount during an eight-day study ate about 550 more calories a day during that time. A 2012 study published in the “American Journal of Physiology” revealed subjects limited to four hours of sleep a night over five days ate more carbohydrates and fat, felt hungrier and recorded a decrease in metabolic rate compared to when they slept nine hours a night. While eating more than three meals a day has been determined to have only a minimal effect on decreasing the amount you eat, eating fewer than three meals a day increases caloric intake. Portion size also affects how much you eat. Research published in the “Journal of Health Psychology” determined that women given 600-gram meal portions consumed nearly 90 more calories than those given 350-gram meal portions -- despite being informed and educated that excessive portion size leads to overeating.

Malnutrition

Definition

Malnutrition is the condition that develops when the body does not get the right amount of the vitamins, minerals, and other nutrients it needs to maintain healthy tissues and organ function.

Effects of defiency in proteins, vitamins and minerals on health

Proteins

If the foods you eat provide you with too few amino acids, especially essential amino acids, your body breaks down protein-rich tissues – your muscles, for example – to access them. Therefore, the initial effect of low protein intake can be muscle wasting accompanied by increasing weakness. You may also experience a greater number of infections because your immune system can’t produce enough antibodies or other immune molecules. You might become increasingly irritable and develop a skin rash and changes to your hair texture. Extreme protein deficiency can result in shock and eventual death.

Proteins

Humans must consume vitamins periodically but with differing schedules, to avoid deficiency. The human body's stores for different vitamins vary widely; vitamins A, D, and B12 are stored in significant amounts in the human body, mainly in the liver,[ and an adult human's diet may be deficient in vitamins A and D for many months and B12 in some cases for years, before developing a deficiency condition. However, vitamin B3 (niacin and niacinamide) is not stored in the human body in significant amounts, so stores may last only a couple of weeks. For vitamin C, the first symptoms of scurvy in experimental studies of complete vitamin C deprivation in humans have varied widely, from a month to more than six months, depending on previous dietary history that determined body stores.

Deficiencies of vitamins are classified as either primary or secondary. A primary deficiency occurs when an organism does not get enough of the vitamin in its food. A secondary deficiency may be due to an underlying disorder that prevents or limits the absorption or use of the vitamin, due to a "lifestyle factor", such as smoking, excessive alcohol consumption, or the use of medications that interfere with the absorption or use of the vitamin. People who eat a varied diet are unlikely to develop a severe primary vitamin deficiency. In contrast, restrictive diets have the potential to cause prolonged vitamin deficits, which may result in often painful and potentially deadly diseases.

Well-known human vitamin deficiencies involve thiamine (beriberi), niacin (pellagra), vitamin C (scurvy), and vitamin D (rickets). In much of the developed world, such deficiencies are rare; this is due to (1) an adequate supply of food and (2) the addition of vitamins and minerals to common foods, often called fortification. In addition to these classical vitamin deficiency diseases, some evidence has also suggested links between vitamin deficiency and a number of different disorders.

Definition

Overnutrition is defined as the overconsumption of nutrients and food to the point at which health is adversely affected.(3) Overnutrition can develop into obesity, which increases the risk of serious health conditions, including cardiovascular disease, hypertension, cancer, and type-2 diabetes.

Until recently, overnutrition had been viewed as a problem that only affected developed nations. However, overnutrition is a growing problem worldwide. The World Health Organization (WHO) describes the current problem: “In the poorest countries, even though infectious diseases and undernutrition dominate their current disease burden, the major risk factors for chronic diseases are spreading. The prevalence of overweight and obesity is increasing in developing countries, and even in low-income groups in richer countries.”(4) Problems of overnutrition are increasing even in countries where hunger is prevalent. In 2002, the WHO reported that the levels of overweight and obese women in the Eastern Mediterranean region and North Africa exceed those in the United States, while levels of overweight and obese women in Eastern Europe and Latin America are similar to those in the United States. Furthermore, obesity is now becoming a marker of poverty in a growing number of nations, including Brazil and Mexico

Effect of excessive intake of :

Carbohydrate

Carbohydrates turn into glucose, which your body burns immediately or converts to glycogen to be stored in the muscles and liver for between meals. If you eat more calories from carbs or other sources than your body can use, the cells store the excess as fat.

Lipids

When you consume more protein than your body needs, the excess protein is used to provide your body with energy or turned into fat. You can't store extra amino acids or protein for later use, so if you consume too many calories in an effort to increase your protein intake you will gain weight. Dehydration.

Vitamins

Taking a vitamin or supplement as directed on the package label is considered to be safe, but not following directions can lead to problems."Excesses of all nutrients, from water, to iron, to water-soluble B vitamins, can potentially cause toxicities," says Norman Hord, PhD, MPH, RD, associate professor in the department of Food Science and Human Nutrition at Michigan State University. People who take vitamins and minerals in amounts above the established upper limits of the Dietary Reference Intakes (DRIs) may harm tissues where the vitamin is stored in their body, Hord explains. That’s why you shouldn’t take more than the recommended amount.Vitamins and other nutrients play essential roles in maintaining good health, but they need to be consumed in the proper amounts. Vitamins are classified into two types: water-soluble vitamins and fat-soluble vitamins. They are divided into these groups according to how they are dissolved and stored in your body. Fat-soluble vitamins reside in your body's fatty tissue and liver and are used as needed by your body. By contrast, water-soluble vitamins dissolve in water and generally are not stored in your body.

Minerals

When taken into the body in high doses, minerals can produce toxic effects. High levels of iodine in the bloodstream can interfere with hormone functioning. Too much sodium can cause confusion, seizures, coma and even death. Selenium is a mineral that is toxic in just small doses. Symptoms include black fingernails and the smell of garlic on your breath and skin. Boron can be toxic in quantities of more than 100 mg causing symptoms such as vomiting, diarrhea, rash, shock and coma. Phosphorus toxicity prevents the absorption of calcium and magnesium in the body. When ingested in amounts more than 1 g daily, phosphorus can cause diarrhea or lead to calcification of organs and soft tissues.

A diet

One of the most important improvements you can make to your diet is to limit saturated fats and entirely cut out trans fats. Both types of fat raise your LDL, or “bad” cholesterol level, which can increase your risk for heart attack and stroke. Trans fat also lowers your levels of HDL or “good cholesterol, which can put you at increased cardiovascular risk. Luckily, there are many ways to control how much saturated and trans fats you take in and replace them with foods that lower your cholesterol.

Avoid foods containing high levels of saturated fats or trans fats—such as potato chips and packaged cookies. These foods can increase your cholesterol levels much more significantly than cholesterol-containing foods such as eggs.

Limit solid fat. Reduce the amount of solid fats like butter, margarine, or shortening you add to food when cooking or serving. Instead of cooking with butter, for example, use olive oil or flavor your dishes with herbs or lemon juice. You can also limit solid fat by trimming fat off your meat or choosing leaner, healthier proteins.

Substitute. Swap out high-fat foods for their lower-fat counterparts. Choose 1% or skimmed milk instead of whole milk, soft margarine for butter, and lean meats like chicken and fish in place of ribs or ground meat. When cooking, use liquid oils like canola, olive, safflower, or sunflower, and substitute two egg whites for one whole egg in a recipe. These substitutions can save you an entire day’s worth of saturated fat.

Be label-savvy. Check food labels on any prepared foods. Many meals and snacks—even those labeled "reduced fat" or "low cholesterol" —may be made with oils containing trans fats. One clue that a food has some trans fat is the phrase "partially hydrogenated." And look for hidden fat; refried beans may contain lard, or breakfast cereals may have significant amounts of fat (as well as lots of heart-risky sugar). Change your habits. The best way to avoid saturated or trans fats is to change your lifestyle practices. Instead of chips, snack on fruit, vegetables, or unsalted nuts. At restaurants, ask that sauces or dressings be put on the side—or left off altogether.

Make smart choices. Choose foods rich in unsaturated fats, fiber, and protein. Fruits, vegetables, fish, beans, nuts, and seeds are all great cholesterol regulators. The best foods for lowering cholesterol are oatmeal, fish, walnuts (and other nuts), olive oil, and foods fortified with sterols or stanols—substances found in plants that help block the absorption of cholesterol—such as corn, beans, peanut butter, almonds, oranges, apples, and avocados.

Ways to reduce the risk of :

1. Blood Pressure Diet - Eat less salt

Too much salt raises your blood pressure, so it is important to eat as little as possible. In fact, some people with high blood pressure may be able to avoid blood pressure medicines by cutting down on salt.

Most of the salt you eat is not what you add to your food, but is in prepared foods like bread, breakfast cereals and ready meals.

Don’t add salt to food when cooking or at the table. When shopping for food, check the labels and choose low-salt options when you can.

2.Diabetes mellitus

Control Your Weight

Excess weight is the single most important cause of type 2 diabetes. Being overweight increases the chances of developing type 2 diabetes seven fold. Being obese makes you 20 to 40 times more likely to develop diabetes than someone with a healthy weight. (8)

Losing weight can help if your weight is above the healthy-weight range. Losing 7 to 10 percent of your current weight can cut your chances of developing type 2 diabetes in half.

Get Moving—and Turn Off the Television

Inactivity promotes type 2 diabetes. (16) Working your muscles more often and making them work harder improves their ability to use insulin and absorb glucose. This puts less stress on your insulin-making cells.

Long bouts of hot, sweaty exercise aren’t necessary to reap this benefit. Findings from the Nurses’ Health Study and Health Professionals Follow-up Study suggest that walking briskly for a half hour every day reduces the risk of developing type 2 diabetes by 30 percent. (18, 19) More recently, The Black Women’s Health Study reported similar diabetes-prevention benefits for brisk walking of more than 5 hours per week. (20) This amount of exercise has a variety of other benefits as well. And even greater cardiovascular and other advantages can be attained by more, and more intense, exercise.

Television-watching appears to be an especially-detrimental form of inactivity: Every two hours you spend watching TV instead of pursuing something more active increases the chances of developing diabetes by 20 percent; it also increases the risk of heart disease (15 percent) and early death (13 percent). (17) The more television people watch, the more likely they are to be overweight or obese, and this seems to explain part of the TV viewing-diabetes link. The unhealthy diet patterns associated with TV watching may also explain some of this relationship.

Tune Up Your Diet

Four dietary changes can have a big impact on the risk of type 2 diabetes.

3.osteoporosis

Increase your calcium intake. Both calcium and vitamin D are essential for bone health. You can make sure that you're getting the daily recommended doses of each by taking a daily calcium supplement — adults require about 1,000 mg of calcium per day — and by getting 15 minutes of sunlight (since vitamin D is made naturally in the body during sunlight exposure). Vitamin D supplements of 400 IU can also help with calcium absorption.

Engage in weight-bearing exercise. “The importance of weight-bearing exercise in osteoporosis prevention can’t be overstated. We recommend beginning early,” says Kaye. Regularly engaging in weight-bearing exercises, like running, walking, strength training, aerobics, jumping rope, and yoga — anything that requires your bones to support your weight — will help strengthen the integrity of your bones.

Revamp your diet. Calcium, vitamin D, and magnesium are important, but you also need to have the energy and ability to remain active. Kaye says this means that for some women, a low-calorie diet may be needed to control obesity so they can be active and engaged. A diet high in salt or caffeine may also contribute to bone loss. Talk to your doctor or a dietitian if you are not sure about the overall quality of your diet.

Maintain a healthy body weight. Your bones have the best shot at long-term health if you are neither over- nor underweight.

Toss the soda. Carbonated beverages have been shown to contribute to bone loss. This may be because the carbonation affects calcium levels in bones, or it may be because if you are drinking soda or sparkling water, you are not drinking a more nutritious beverage such as milk or fortified orange juice, which can help build stronger bones.

Stop smoking. There is an association between smoking and an increased risk of osteoporosis.

Methods used to improve the quality and quantity of food production through the following

Direct seeding for rice