BIOLOGY:
NUTRITION
ü Nutrition is the supply to cells and organisms, of the materials necessary to support life
ü Many common health problems can be prevented by a healthy diet
ü A poor diet can have injurious impact on health, leading to problems such as scurvy, beriberi and kwashiorkor
ü A healthy diet can also significantly prevent and mitigate systemic diseases like cardiovascular disease, diabetes and osteoporosis
ü Eating a wide variety of fresh, unprocessed food has proven favourable compared to monotonous diets of processed food
ü Consumption of whole plant foods slows digestion, allows better absorption and a more favourable balance of nutrients
Nutrients
ü There are six major classes of nutrients: carbohydrates, fats, minerals, proteins, vitamins and water
ü These can be classified into
v Macronutrients: nutrients needed in large quantities. These include carbohydrates, fats, proteins and water. Fibre is another macronutrient whose functions have not been fully understood
v Micronutrients: nutrients needed in smaller quantities. These include minerals and vitamins. Antioxidants and phytochemicals are micronutrients as well, but their functions are not well understood
ü Most foods contain a mixture of nutrients
ü Some nutrients may be stored internally (eg. Fat soluble Vitamins) while others are required more or less continuously
Carbohydrates
ü Carbohydrates are sugars, and are classified as monosaccharides, disaccharides or polysaccharides depending on the number of monomer (sugar) units they contain
ü Carbohydrates constitute a large part of foods such as rice, noodles, bread and other grain based products
ü In general, simple saccharides are easier to digest and absorb than polysaccharides
ü Since they are absorbed more quickly, simple carbohydrates lead to elevated levels of blood glucose
Fibre
ü Dietary fibre is a carbohydrate (polysaccharide) that is incompletely absorbed in humans and some animals
ü Like all carbohydrates, when metabolised it produces energy
ü However, it does not contribute much energy due to limitations on its absorbability and digestion
ü Dietary fibre consists mainly of cellulose, a polysaccharide that is indigestible in humans
ü Whole grains, fruits and vegetables are good sources of fibre
ü Fibre provides bulk to intestinal contents and stimulates peristalsis – the rhythmic muscular contractions of the intestines that moves digesta along the digestive tract
ü For these reasons, fibre is important for digestive health. It helps alleviate constipation and diarrhoea and is said to reduce colon cancer
Fats
ü Fat consists of fatty acids bonded to glycerol. Fatty acids are carboxylic acids that contain long chains of carbon and hydrogen atoms
ü They are typically found as triglycerides
ü Fats are classified as
v Saturated fats: have all the carbon atoms in the fatty acid chains bonded to hydrogen atoms
v Unsaturated fats: have some carbon atoms double bonded to themselves, thereby have fewer hydrogen atoms
ü Studies have shown that unsaturated fats are preferable to saturated fats in terms of health effects
ü Saturated fats are usually solids at room temperature (eg butter) while unsaturated fats are liquids at room temperature (eg olive oil)
ü Trans fats are a type of unsaturated fat with trans-isomer bonds. These are rare in nature and usually created by an industrial process called hydrogenation. Trans fats are harmful to health (coronary heart disease) and their use is to be avoided
Proteins
ü Proteins are the basis of many animal body structures and form enzymes that control chemical reactions in the body
ü Proteins are composed of amino acids, which contain nitrogen atoms
ü The body requires amino acids to produce new proteins and replace damaged proteins
ü Since the body cannot store protein, amino acids must be present in the daily diet
ü Diet with adequate proteins is especially important during early development and maturation, pregnancy, lactation or injury
ü A complete protein source is one that contains all essential amino acids
ü Sources of protein include meat, tofu, soy, eggs, grains, legumes and dairy products
ü A few amino acids can be converted into glucose for energy (called gluconeogenesis). This process mainly happens only during starvation
Minerals
ü Dietary minerals are the chemical components required by living organisms other than the four elements carbon, oxygen, nitrogen, hydrogen that are present in nearly all organic molecules
ü Dietary minerals include some metals as well (sodium, potassium) which are usually found in ionic state
ü Minerals are recommended to be supplied in the daily diet
ü Most famous dietary mineral is iodine (added to salt) which prevents goitre
ü Macrominerals (required more than 200 mg/day) include
v Calcium: electrolyte, also needed for structural growth (teeth, bones)
v Chlorine: electrolyte
v Magnesium: required for processing ATP (energy)
v Phosphorous: required component of bones, essential for energy processing
v Potassium: electrolyte (heart and nerve health)
v Sodium: common electrolyte, needed in large quantities. Most common source is common salt. Excess sodium depletes calcium and magnesium leading to high BP an osteoporosis
v Sulphur: essential for certain amino acids and proteins
ü In addition to the macrominerals, many other minerals are required in trace amounts. These include cobalt, copper, chromium, iodine, iron, manganese, molybdenum, nickel, selenium, vanadium, zinc
Vitamins
ü A vitamin is an organic compound required as a nutrient in tiny amounts by an organism
ü A compound is called a vitamin when it cannot be synthesised in sufficient amounts by an organism, and must be obtained from the diet
ü Thus, the term “vitamin” is conditional both on the circumstance and the organism. For instance ascorbic acid is termed Vitamin C for some organisms but not for others, and Vitamins D and K are required in the human diet only under certain circumstances
ü Vitamins must be supplied in the diet (except Vitamin D, which can be synthesised by the skin in the presence of UV radiation)
ü Fresh fruits and vegetables are good sources of vitamins
ü Vitamin deficiencies may results in diseases like goitre, scurvy, osteoporosis, impaired immune system etc
ü Excess of some vitamins can also be dangerous: excess Vitamin A can cause jaundice, nausea, blurry vision, vomiting, muscle pain etc
Water
v About 70% of non-fat mass of the body is water
v To function properly, the body requires between one and seven litres of water every day
v It is recommended that daily water intake for an adult male be 3.7 l and for females be 2.7. However, these requirements vary with climate, activity level and other factor
v Too little water can lead to dehydration
v Too much water can lead to water intoxication, a potentially fatal disturbance to the brain. However, this is very rare in normal humans and usually only occurs during water drinking contests or intense bouts of exercises when electrolytes are not replenished
Malnutrition
Nutrients | Deficiency | Excess |
Carbohydrates | Low energy | Diabetes, obesity |
Fats | None | Cardiovascular disease, obesity |
Cholesterol | none | Cardiovascular disease |
Protein | Kwashiorkor (edema, anorexia, inadequate growth) | Rabbit starvation (diarrhoea, headache, low BP, low heart rate, Discomfort/hunger that can only be satisfied by eating fats and carbohydrates.) |
Sodium | Hyponatremia (electrolyte imbalance) | Hypernatremia, hypertension |
Iron | Anaemia | Cirrhosis (chronic liver disease), heart disease |
Iodine | Goitre, hypothyroidism | Iodine toxicity |
Vitamin A | Night blindness, xeropthalmia (dry eyes) | Hypervitaminosis A (birth defects, liver problems, osteoporosis) |
Vitamin B1 | Beri-beri | |
Vitamin B2 | Cracking of skin | |
Vitamin B12 | Pernicious anaemia | |
Niacin (Vitamin B3) | Pellagra (diarrhoea, dermatitis, dementia, death) | Dyspepsia (indigestion), cardiac arrhythmias |
Vitamin C | Scurvy | Diarrhoea |
Vitamin D | Rickets | Hypervitaminosis D (dehydration, vomiting, constipation) |
Vitamin E | Nervous disorders | Hypervitaminosis E (anticoagulant) |
Vitamin K | Haemorrhage | |
Calcium | Osteoporosis | Fatigue, vomiting, depression, cardiac arrhythmias |
Magnesium | Hypertension | Weakness, nausea, vomiting |
Potassium | Hypokalaemia, cardiac arrhythmias | Hyperkalaemia, palpitations |
BIOLOGY: VACCINES
ü A vaccine is a biological preparation that improves immunity to a particular disease
ü Vaccines were first used by Edward Jenner (England) in the 1770s to inoculate against small pox using the cow pox microbe
ü Vaccines have resulted in the eradication of small pox, one of the most contagious and deadly diseases known to man
ü Other diseases like polio, measles, mumps, typhoid etc are have been significantly reduced. Currently, polio is prevalent in only four countries: Afghanistan, Pakistan, Nigeria and India
Mechanism of action
ü A vaccine is usually made from a weakened or dead form of the microbe that it is intended to fight
ü It stimulates the body’s immune system to recognise the microbe as foreign, and destroy it and remember it
ü When the same microbe re-appears later, the immune system easily recognises and destroys it
ü When the body recognises the virulent microbe attack, it
v Neutralises the target microbe before it can enter body cells
v Destroys infected cells before the microbe can spread to other cells and multiply
Types of vaccines
ü Killed vaccines: these are vaccines that contain micro-organisms that have been killed using chemicals or heat. Eg: influenza, cholera, bubonic plague, polio, hepatitis A
ü Attenuated vaccines: these contain live attenuated (numerous) micro-organisms. These are usually live viruses that have been cultivated under conditions which disable their virulent properties, or use closely-related by less dangerous micro-organisms.These vaccines provide more durable immune response and are preferred type for healthy adults. Eg: yellow fever, measles, rubella, mumps, typhoid
ü Toxoid vaccines: inactivated toxic compounds that cause illness. Eg: tetanus, diphtheria
ü Subunit vaccines: these use protein subunits instead of the entire micro-organism as a vaccine. Eg: Hepatitis B vaccine (which uses only surface proteins), Human Papilloma Virus (HPV) vaccine (which uses subunits of influenza virus)
Effectiveness of vaccines
ü Vaccines do not guarantee complete protection from a disease
ü This could be due to
v Host’s immune system may not respond adequately
v Host may have lowered immunity (such as due to diabetes, HIV, steroid use etc)
v Host may not have a B cell capable of producing antibodies to that particular antigen
ü The efficacy of a vaccine depends on a number of factors
v The disease itself
v The strain of vaccine
v Following the schedule of vaccinations
v Individual host factors
v Genetic and ethnic predisposition
ü Most vaccines use adjuvants to boost immune system response. Adjuvants are compounds added to the vaccine that increase the immune response, without having any specific antigenic effect by themselves.
ü Aluminum salts like aluminium phosphate and aluminium hydroxide are the most common adjuvants used
List of important vaccines
Vaccine | Disease | Type | Notes |
Anthrax vaccine | Anthrax | Protein subunit | |
Bacillus Calmette-Guerin (BCG) | Tuberculosis | Live bacteria | |
DTP | Diphtheria, Pertussis (whoopoing cough), Tetanus. | ||
Gardasil (Human Papilloma Virus (HPV)) | Cervical cancer | Protein subunit | |
Polio vaccine | Polio | Killed/inactivated | Polio is prevalent only in humans Currently polio has been eradicated from all countries except Afghanistan, Pakistan, Nigeria and India |
MMR | Measles, Mumps, Rubella | ||
Meningococcal vaccine | Meningococcus | ||
Rabies vaccine | Rabies | Attenuated | |
Yellow fever vaccine | Yellow fever | Attenuated |
MEDICINAL CHEMISTRY
ü Medicinal chemistry involves the design, synthesis and development of pharmaceutical drugs
ü Compounds used as medicines are overwhelmingly organic compounds including small molecules and biopolymers. However, some inorganic compounds and metals have been found to have medicinal properties as well
Classes of drugs
Class of drug | Application | Example | Notes |
Antipyretics | Reduce body temperature | Aspirin, paracetamol (acetaminophen) | Antipyretics cause the hypothalamus to override an increase in temperature Taking antipyretics in empty stomach can cause ulcer |
Analgesics | Pain relief | Paracetamol Non steroidal anti inflammatory drugs (NSAIDS) Morphine | Some antipyretics act as analgesics as well Some narcotics (heroin, morphine, marijuana) can also act as analgesics |
Tranquilizers | Induce sedation | Barbiturates, antihistamines | Sedatives cause sleep, poor judgement, slow reflexes Excessive use can cause unconsciousness and even death |
Antiseptics | Reduce possibility of infection | Boric acid, hydrogen peroxide, iodine | Antiseptics are applied externally to living tissues Antiseptics also reduce body odour caused due to bacterial decomposition They are used in breath freshners and deodorants |
Antibiotics | Kill bacteria | Penicillin, gramicidin, amoxicillin, streptomycin | An antibiotic is defined as a substance produced by a microorganism that kills other microorganisms Antibiotics are considered life-saving drugs |
Diuretics | Increases rate of urination | Amiloride, triamterene | |
Vasodilators | Widen blood vessels | Histamine, nitric oxide | Decrease blood pressure Increase blood flow |
Vasoconstrictors | Narrow blood vessels Staunch blood loss due to haemorrhage | Antihistamines, cocaine, LSD, caffeine | Increase blood pressure Decrease blood flow Make skin look paler because less blood reaches the skin |
Anaesthetics | Cause loss of sensation | Cocaine, nitrous oxide, halothane | General anaesthetics cause a loss of consciousness Local anaesthetics cause loss of sensation in a specific part of the body |
Antifungals | Fungal diseases like ringworm, athlete’s foot, meningitis | Ketoconazole, benzoic acid, neem seed oil, tea tree oil | Since both fungi and human cells are eukaryotes, the possibility of side effects is higher than in anti-bacterial drugs (like antibiotics) |
Antivirals (Antiretrovirals) | Inhibit growth of virus | Zedovudine, lamivudine | Unlike antibiotics, antiviral drugs do not destroy target microbes but only inhibit their growth Designing antiviral drugs is difficult because virus use host’s cells to replicate Some virus, like influenza and HIV, mutate rapidly which means they can be treated with antivirals only and not be prevented by vaccines Antiretrovirals are a subclass of antivirals that treat retroviruses such as HIV |
Some important common drugs
Drug | Classification | Application | Notes |
Penicillin | Antibiotic | Syphilis, staphylococcal infections (food poisoning) | Narrow spectrum antibiotic (treats only a narrow range of diseases) |
Zedovudine | Antiviral | HIV | |
Lamivudine | Antiviral | Hepatitis B | |
Streptomycin | Antibiotic | Tuberculosis | |
Erythromycin | Antibiotic | Respiratory tract infections | |
Ciprofloxacin | Antibiotic | Urinary tract infections, common pneumonia, myoplasmal infections | Broad spectrum antibiotic |
Amoxicillin | Antibiotic | Wide range of infections | Broad spectrum |
Tetracycline | Antibiotic | Cholera | |
Chloroquine | Antibiotic | Malaria | |
Aspirin | Analgesic, Antipyretic | Fever, pain | One of the most widely used medications in the world |
Paracetamol (Acetaminophen) | Analgesic, antipyretic | Fever, pain |
BIOLOGY: CLONING
ü Cloning is the process by which genetically identical individuals are produced
ü Cloning happens in nature by the biological mechanisms of asexual reproduction in bacteria, insects and plants
ü Cloning can also be performed artificially by copying fragments of DNA (molecular cloning) or cells (cell cloning) or organisms
ü Mammals, which reproduce sexually, cannot clone naturally. Mammals inherit genetic material half each from both parents, meaning that the progeny is never an identical replica of the parent. Natural clones in mammals are confined to the production of identical twins
ü The first vertebrate to be cloned was a tadpole by Robert Briggs (USA) and Thomas King (USA) in 1952
Cloning in plants
ü Plants have been clone for a long time.
ü Grafting is a form of plant cloning
ü Many horticulture plants are cloned, having been derived from a single individual
ü Examples of plant cloning include carrots, tobacco, potato, banana
Cloning in animals
ü Cloning of animals is based on a technique known as “somatic cell nuclear transfer”.
ü Nuclear transfer involves fusing two cells together – a donor cell containing all its DNA, and egg cell with all its DNA removed
ü The two cells are fused with an electric pulse and the resulting enucleated egg is implanted in the mother
Dolly the Sheep
ü Dolly, a Finn Dorset ewe, was the first mammal to be successfully cloned from an adult cell
ü Dolly was cloned by Ian Wilmut and Keith Campbell at the Roslin Institute in Edinburgh (Scotland)
ü Dolly was born in 1996 and lived for six years
ü The donor cell for Dolly was taken from a mammary gland.
ü Production of a healthy clone proved that a cell from a specific part of the body could recreate a whole individual
Some animals that have been cloned
Cloned animal | When | Where | By whom | Notes |
Tadpole | 1952 | USA | Robert Briggs, Thomas King | |
Carp (fish) | 1963 | China | Tong Dizhou | |
Mice (first cloned mammal) | 1986 | Soviet Union | Chaylakhyan, Veprencev, Sviridova, Nikitin | First cloned mammal |
Sheep (first cloned mammal from adult cell) | 1996 | Britain | Ian WIlmut, Keith Campbell | First cloned mammal from adult cell |
Rhesus monkey (named Tetra) | 2000 | It was named Tetra | ||
Gaur (Asian Ox) | 2001 | USA | Jonathan Hill, Philip Damiani | Named Noah First endangered species to be cloned |
Cat | 2001 (Copycat) 2004 (Little Nicky) | USA | Copycat was the first cloned pet Little Nicky was the commercially produced cat clone | |
Mule (named Idaho Gem) | 2003 | USA | Gordon Woods, Dirk Vanderwall | First clone in horse family |
Horse (named rometea) | 2003 | Italy | Cesare Galli | First cloned horse First animal to be born from and carried by its cloning mother |
Water buffalo (called Samrupa) | 2009 | India | S K Singla and others at Karnal National Dairy Research Institute | First cloned buffalo Died 5 days after birth due to lung infection |
Camel (called Injaz) | 2009 | Dubai | Nisar Ahmad Wani | First cloned camel |
BIOLOGY: GENETIC ENGINEERING
ü Genetic engineering refers to the direct manipulation of an organism’s genes
ü Genetic engineering is also referred to as recombinant DNA technology, genetic modification and gene splicing
ü Genetic engineering uses cloning and transformation of molecules to alter the structure and characteristics of genes
ü Examples of genetic engineering include improved crop technologies, synthetic hormones, and creation of experimental mice
Process of genetic engineering
The process of genetic engineering has five main steps:
1. Isolation of the genes of interest
2. Insertion of the genes into a transfer vector
3. Transfer of the vector to the organism to be modified
4. Transformation of the cells of the organism
5. Selection of the genetically modified organisms from those that have not been successfully modified
Applications of genetic engineering
ü The first genetically engineered medicine was synthetic insulin
ü Genetic engineering has been used to produce vaccines for hepatitis B
ü Creation of genetically modified foods such as soybean, corn, canola and cotton seed oil. GM foods have higher resistance to pests, bacterial/fungal infections, higher yield and higher nutritional value
ü Gene therapy using viruses to treat severe combined immunodeficiency (SCID)
ü Using genetically modified virus to construct environment friendly lithium-ion battery
ü Using human eggs from a second mother to allow infertile women with genetic defects in their mitochondria to have children
ü Artificial DNA, called Synthetic Organism (SO-1), with unknown functions has been created
Milestones in genetic engineering
ü 1953: James Watson (USA) and Francis Crick (Britain) discover structure of DNA. They win Nobel in Physiology or Medicine in 1979
ü 1973: Stanley Cohen (USA) and Herbert Boyer (USA) develop a technique to clone segments of DNA molecules
ü 1976: Genentech, the first company dedicated to producing genetically engineered products is established in San Francisco. It was founded by Herbert Boyer and Robert Swanson
ü 1979: Genetic engineering used to synthesize insulin
ü 1981: scientists at Ohio university transfer genes from other organisms into mice
ü 1990: Human Genome Project launched
ü 1990: first gene therapy experiment performed on a four-year old girl with adenosine deaminase deficiency. Developed by French Anderson
ü 1996: a yeast known as Saccharomyces cerevisiae is the first eukaryotic genome to be sequenced by more than 100 labs collaboratively around the world
ü 2003: Human Genome Project announces complete mapping of human genome
GENETICALLY MODIFIED FOODS
1. BT-Cotton
1. BT-Cotton is a genetically modified variety of cotton into which Cryiae gene from the bacillus thuriegenois bacteria have been introduced
2. This gene produces a toxin called BT-Toxin in every part of the plant thereby destroying the dreaded cotton pest Bollworm
3. This technology was developed by US seed company Monsanto
4. However, concerns include evolution of super-pests with higher levels of resistance, destruction of agriculturally beneficial organisms like bees, soil microflora etc
2. Terminator gene
1. Terminator gene is a seed variety developed using genetic engineering
2. It causes the seed to self-destruct after it has been used to raise the first generation of crops
3. This is done in order to prevent farmers from raising subsequent generations of crops without paying royalties
4. Concerns include this self-destruct gene may be transferred to other plants by cross-pollination leading to extinction of traditional agricultural production
5. It is also known as Genetic Use Restriction Technology (GURT) and was developed by the US Department of Agriculture in conjunction with the Delta and Pine Land Co.
3. Golden rice
1. Type of rice crop provided with a gene to develop Beta-Carotene
2. This helps production of vitamin A in the body
3. This helps fight vitamin A deficiency, the primary cause of childhood blindness
4. Beta-carotene gives rice a yellow colour and hence is called Golden Rice
5. Created by Swiss Federal Institute of Technology
4. GM Cabbage
1. Cabbage that will resistant to attack of Diamond Back Moth
2. Developed by Indian Agricultural Research Institute (New Delhi)
BIOLOGY: GENETIC DISORDERS
About genetic disorders
Huntington's disease is inherited in the autosomal dominant fashion
ü Genetic disorders are disorders that are passed on from generation to generation
ü They are caused by abnormalities in genes or chromosomes
ü Some genetic disorders may also be influenced by non-genetic environmental factors. Eg: cancer
ü Most genetic disorders are relatively rare and only affect one person in thousands or millions
ü To recollect, males have XY chromosome pairs while females have XX pairs
Single Gene Disorders
ü Single gene disorders result from the mutation of a single gene
ü They can be passed onto subsequent generations in multiple ways
ü Single gene disorders include sickle cell disease, cystic fibrosis Huntington disease
Multiple gene disorders
ü Multiple gene disorders result from mutation on multiple genes in combination with environmental factors
ü They do not have a clear pattern of inheritance, which makes it difficult to assess risk of inheriting a particular disease
ü Examples include heart disease, diabetes, hypertension, obesity, autism
TYPES OF SINGLE GENE GENETIC DISORDERS
1. Autosomal dominant
Sickle cell disease is inherited in the autosomal recessive pattern
1. Only one mutated copy of the gene is necessary for inheritance of the mutation
2. Each affected person usually has one affected parent
3. There is a 50% chance that the child will inherit the mutated gene
4. Autosomal dominant disorders usually have low penetrance i.e. although only one mutated copy is needed, only a small portion of those who inherit that mutation will develop the disorder
5. Eg: Huntington’s disease, Marfan syndrome
2. Autosomal recessive
1. Two copies of the gene must be mutated for a person to be affected
2. An affected person usually has unaffected parents who each have one mutated gene
3. There is a 25% chance that the child will inherit the mutated gene
4. Eg: Cystic fibrosis, sickle cell disease, Tay-Sachs disease, dry earwax, Niemann-Pick disease
3. X-linked dominant
1. X-linked dominant disorders are caused by mutations on the X chromosome
2. Males and females are both affected by such disorders. However, males are affected more severely
3. For a man with a X-linked dominant disorder, his sons will all be unaffected (since they receive their father’s Y chromosome)while his daughters will all be affected (since they receive his X chromosome)
4. A woman with a X-linked dominant disorder has a 50% chance of passing it on to progeny
5. Eg: Hypophosphatemic rickets, Rett syndrome, Aicardi syndrome
4. X-linked recessive
X-linked recessive with a carrier mother
1. Caused by mutations on the X-chromosome
2. Males are affected more frequently than females
3. The sons of a man affected by a X-linked recessive disorder will not be affected, while his daughters will carry one copy of the mutated gene
4. The sons of a woman affected by a X-linked recessive disorder will have have a 50% chance of being affected by the disorder, while the daughters of the woman have a 50% chance of becoming carriers of the disorder
5. Eg: colour blindness, muscular dystrophy, hemophilia A
5. Y-linked disorders
1. Caused by mutations on the Y chromosome
2. Y chromosomes are present only in males
3. The sons of a man with Y-linked disorders will inherit his Y chromosome and will always be affected while the daughters will inherit his X chromosome and will never be affected
4. Eg: male infertility
6. Mitochondrial disorders
1. These disorders are caused by mutations in the mitochondrial DNA
2. Only mothers can pass on mitochondrial disorders to children, since only egg cells (from the mother) contribute mitochondria to the developing embryo
3. Eg: Leber’s Heriditary Optic Neuropathy
BIOLOGY: GENETICS
History of genetics research
ü The father of genetics is Gregor Mendel (Austria-Hungary). In 1866 he published the principle known as Mendelian Inheritance which described the concept of inheritance between parent organisms and offspring
ü In 1869 Friedrich Miescher (Switzerland) discovered DNA
ü 1880: Walther Flemming (Germany) describes division of chromosomes
ü 1933: Jean Brachet (Belgium) establishes DNA is found in chromosomes and RNA in cell cytoplasm
ü 1944: Oswald Theodore Avery, Colin McLeod, Maclyn McCarty (US) identify DNA as genetic material
ü 1953: James Watson and Francis Crick (US) establish double helix structure of DNA. They win the Nobel Prize in Physiology or Medicine in 1962 for this discovery
ü 1968: Hargobind Khorana, Robert Holley and Marshall Nirenberg (US) demonstrate the role of RNA in protein synthesis. Nobel in Medicine 1968
ü 1977: Frederick Sanger (UK) sequences DNA for the first time. He produce the entire genome of bacteriophage X174. Nobel in Chemistry in 1980
ü 1983: Kary Mullis (US) discovers polymerace chain reaction enabling easy amplification of DNA. Nobel in Chemistry 1993
ü 1995: The genome of Haemophilus influenzae is the first genome of a living organism to be sequenced
ü 2001: First draft sequence of the human genome
ü 2003: Human Genome Project successfully completed
DNA
ü DNA (deoxyribonucleic acid) is the basis for genetic inheritance. However, certain viruses use RNA for genetic information
ü DNA is composed of a chain of nucleotides. There are four types of nucleotides: adenine (A), cytosine (C), guanine (G), thymine (T)
ü DNA usually exists in a double-helix structure molecule
ü Each nucleotide in one strand of the double-helix pairs with a particular partner nucleotide in the other strand. A pairs with T and C pairs with G
Chromosome
ü Genes are regions within DNA. Genes are arranged in long chains of DNA molecules. These chains are called chromosomes
ü Eukaryotic organisms have DNA arranged in multiple such chromosomes. Bacteria have only one chromosome
ü The combined DNA sequence of all chromosomes is called the genome. This contains all hereditary information of that organism
ü Haploid organisms have only copy of each organism. Eg: male bees, wasps, ants
ü Diploid organisms have two copies of each chromosome. Eg: most plants and animals (including humans). However, in male humans the sex-linked X and Y chromosomes exist only as a single copy.
ü Male: XY, Female: XX
Human Genome Project
ü The Human Genome Project was an international scientific effort to determine the complete genetic code of human beings
ü Launched in 1990, complete results published in 2003
ü Performed by scientists from US, UK, Canada and New Zealand, lead by University of California Santa Cruz
ü Key findings of the project include
v There are approximately 25000 genes in human beings
v All human races are 99.99% alike genetically
v Most genetic mutation occurs in male. Thus males are responsible for genetic evolution and for genetic disorders
ü Human Genome Project mapped nucleotides in haploid sequences. Efforts are currently underway to map diploid sequences as well. Eg: International HapMap Project, Personal Genome Project
BIOLOGY: BIOMOLECULES
1. Lipids
ü They are a broad group of molecules that include fats, fatty acids, sterol, waxes, glycerides and phospholipids
ü Fats are a subgroup of lipids called triglycerides
ü Cholesterol is an example of the type of lipids called sterol
ü The main functions of lipids include energy storage, cell signaling and cell structure
2. Carbohydrates
ü They are organic compounds that contain only carbon, hydrogen and oxygen
ü They belong to 3 types: monosaccharides, disaccharides and polysaccharides
ü Monosaccharides
v Monosaccharides are the simplest form of carbohydrates, and cannot be broken down any further.
v Eg: glucose and fructose
v Monosaccharides dissolve in water, taste sweet and are called “sugars”
v Used as energy source and in biosynthesis
ü Disaccharides
v Disaccharides are compounds made by two monosaccharides bound together.
v Eg: sucrose and lactose
v Like monosaccharides, disaccharides dissolve in water, taste sweet and are called “sugars”
v Used for carbohydrate transport
ü Polysaccharides
v Polysaccharides are compounds made by complex chains of monosaccharides.
v Eg: cellulose, glycogen
v Used for energy storage (glycogen) and for cell walls (cellulose)
v Cellulose is the most abundant organic molecule on Earth
3. Amino acids
ü They are molecules that contain an amine group and a carboxyl group
ü Eg: glycine, monosodium glutamate
ü They are the building blocks of proteins
ü Applications include metabolism, drug therapy, flavour enhancement, manufacture of biodegradble plastics
4. Proteins
ü They are compounds made from amino acids
ü The first protein to be sequenced was insulin, by Frederick Sanger who won the Nobel Prize in Chemistry for this in 1958
ü The first protein structures to be solved were hemoglobin and myoglobin by Max Perutz and Sir John Cowdrey Kendrew in 1958. They won the Nobel Prize in Chemistry for this achievement in 1962
ü Proteins are used as enzymes, in muscle formation, as cell cytoskeleton, cell signaling and immune responses
ü The process of digestion breaks down protein into free amino acids that are then used in metabolism
5. Nucleic acids
ü They are macromolecules formed by chains of nucleotides
ü Common examples include DNA and RNA
ü DNA (Deoxyribonucleic acid)
v Contains two strands of nucleotides arranged in a double helix structure
v In cells, DNA is organized into long structures called chromosomes
v Used primarliy for long term storage of genetic information
v DNA was first isolated by Swiss physician Friedrich Miescher in 1869
v The double helix structure was suggested by James Watson and Francis Crick in 1953. They, alongwith Maurice Wilkins won the Nobel Prize in Physiology or Medicine for this discovery in 1962
ü RNA (ribonucleic acid)
v Contains one strand of nucleic acids
v Less stable than DNA
v Used primarily for protein synthesis
v Messenger RNA carries information from DNA to the ribosome. Translation RNA translates the information in the mRNA
v RNA synthesis was discovered by Severo Ochoa of Spain, for which he won the Nobel Prize in Physiology or Medicine in 1959
Matching cell functions to biomolecules
Function | Biomolecule |
Cell structure | Lipid |
Impact protection | Lipids and proteins |
Enzymes | Proteins |
Energy storage | Carbohydrates, proteins, lipids |
Cell movement and support | Proteins (actin and myosin) |
Protein synthesis | Nucleic acids (RNA) |
Hormones | Proteins |
Immediate cellular energy | Carbohydrates (glucose) |
Electrical and thermal insulation | Lipids |
Storage of amino acids | Proteins |
Genetic information | Nucleic acids (DNA) |
BIOLOGY: BLOOD
ü Blood is a specialized body fluid that delivers necessary substances to various cells (like nutrients and oxygen) and transports waste products away from those cells
ü Blood accounts for 7% of human body weight
ü The average human adult has a blood volume of approx. 5 litres
ü Arteries carry inhaled oxygen-rich blood from the heart to the tissues, while veins carry carbon dioxide rich blood (de-oxygenated) from the tissues to the lungs to be exhaled
SEM image of a RBC, a platelet and a WBC (L to R)
Composition of blood
ü Blood is made of plasma, Red Blood Cells, White Blood Cells (including leukocytes and platelets)
ü Plasma constitutes about 54.3% of blood, RBCs 45% and WBCs about 7%
ü RBCs contain hemoglobin and distribute oxygen to tissues
ü Leukocytes attack and remove pathogens and provide immunity
ü Platelets are responsible for clotting of blood
ü Plasma is the blood’s liquid medium. It circulates dissolved nutrients and removes waste products. By itself, it is yellow in colour
Functions of blood
ü Supply oxygen to tissues
ü Supply nutrients such as glucose, amino acids and fatty acids
ü Remove waste such as carbon dioxide, urea and lactic acid
ü Provide immunity against pathogens
ü Coagulation
ü Transport hormones
ü Regulate pH
ü Regulate core body temperature
Colour of blood
ü Colour is primarily determined by hemoglobin
ü Arterial blood is bright red, due to the presence of oxygen
ü Venous blood is dark red, due to deoxygenation
ü Blood in carbon monoxide and cyanide poisoning is bright red
ü Blood of most molluscs (marine animals like squids, oysters, snails, octopuses etc) is blue due to the presence of copper containing protein hemocyanin
Blood Groups
Blood Group | Can donate to | Can receive from |
A | A and AB | A and O |
B | B and AB | B and O |
AB | AB only | All groups |
O | All groups | O only |
Medical disorders related to blood
Disorder | Cause | Other notes |
Bleeding | An adult can lose 20% of blood volume before the first symptom (restlessness) sets in | |
Dehydration | Loss of volume due to loss of water | |
Atherosclerosis | Reduced blood flow through arteries | |
Thrombosis | Coagulation of blood vessels | |
Hypoxia (lack of oxygen) | Narrowing of blood vessels Problem with pumping action of heart | Can lead to ischemia (tissue with insufficient blood) or to infarction i.e. necrosis (tissue death) |
Anemia (insufficient RBC) | Bleeding, nutritional deficiencies | |
Sickle-cell disease | Mutation of hemoglobin leading to abnormal sickle shape of RBC | Sickle shaped RBCs do not have the flexibility to travel through many blood vessels Extremely painful disease with no known cure Found commonly in malaria-infested areas because sickle cells offer resistance to malaria |
Leukemia | Abnormal proliferation of WBCs in the bone marrow | |
Hemophilia | Dysfunction of clotting mechanism | Lack of coagulation means simple wounds become life-threatening Causes hemarthosis (bleeding into joints), which is painful and crippling Linked to X chromosome Occurs usually in males only |
Thrombophilia | Abnormal propensity to coagulate | |
Blood-borne infections | Infection by a disease-carrying vector | Examples: HIV, Hepatitis, Malaria |
Carbon monoxide poisoning | Carbon monoxide binds to hemoglobin preventing oxygen transport | Body tissues die due to lack of oxygen |