Lesson 8: Cell Biology and Biotechnology

Rule 1: Stem cells — Cell biology (cytology) studies the structure, types, organelles and division of cells. The National Centre for Cell Science (NCCS) is at Pune and Instem is at Bengaluru. Stem cells give rise to all other cell types of a multicellular organism and help in wound healing. The early embryo is a mass of nearly alike cells, the stem cells. By differentiation (विभेदन) they form different tissues; once tissues are formed, their cells mostly produce only the same kind of cells.

In the figure : In the figure stem cells can become many kinds of cells.

• Easy : A cut on your finger heals because stem cells make new skin cells.
• Medium : A stem cell can become a muscle cell, a nerve cell or a blood cell, depending on the signals it receives.
• Exam-type : A mature nerve cell normally makes only nerve cells, while an early embryo cell can form any tissue: this shows that differentiation reduces what a cell can become.

Rule 2: Sources and storage — Sources: the umbilical cord (cord blood), the blastocyst stage of the embryo, and in adults the red bone marrow, adipose (fatty) connective tissue and blood. For preservation, samples are kept in small sterile vials in liquid nitrogen at −135 °C to −190 °C.

In the figure : In the figure sources of stem cells and how they are kept.

• Easy : Cord blood collected at birth can be stored for the child's future medical use.
• Medium : Liquid nitrogen is extremely cold (about −196 °C), so the samples stay frozen and the cells do not die; storage at −135 °C to −190 °C is used.
• Exam-type : Compare: embryonic stem cells come from the embryo; adult stem cells come from tissues such as bone marrow; both can be stored.

Rule 3: Types of stem cells — Embryonic stem cells exist before differentiation, which starts on the 14th day of conception. They can be collected on the 5th to 7th day and can give about 220 types of cells; this property is pluripotency (बहुसक्षमता). The other type is adult stem cells.

• Easy : Differentiation starts on day 14, so embryonic stem cells must be collected before that, on days 5 to 7.
• Medium : About 220 types of cells can arise from embryonic stem cells, which makes them very valuable for therapy.
• Exam-type : The collection window of days 5 to 7 lasts 7 − 5 + 1 = 3 days, and differentiation starts 14 − 7 = 7 days after the last of those days.

Spot the difference

Rule 1: Uses of stem cells — Regenerative therapy: cell therapy replaces dead cells in diabetes, myocardial infarction, Alzheimer's and Parkinson's disease. Blood cells can be produced for anaemia, thalassemia and leukemia. Organs such as the kidney and liver can be produced and transplanted.

• Easy : In type 1 diabetes, stem cells could be made into insulin-making cells to replace the dead ones.
• Medium : Blood cells from stem cells can treat thalassemia, where the body cannot make healthy red cells.
• Exam-type : Growing a kidney from stem cells could remove the long waiting list for donors, but it is still an advanced research area.

Rule 2: Organ donation — A living person can donate one kidney (we have a pair) and skin. Organs such as the liver, heart and eyes are donated after death only (posthumous donation, मरणोत्तर दान). Blood group, age and diseases of donor and recipient must be matched. Organ and body donation save lives, the blind regain vision, and bodies are used for medical research. The Transplantation of Human Organs Act, 1994 (amended in 2009, 2011 and 2014) makes the process transparent.

In the figure : In the figure what can be donated and when.

• Easy : A living donor can give one kidney and still live healthily with the other.
• Medium : The heart and liver can only be donated after death, because a person cannot live without them.
• Exam-type : Matching: a recipient with blood group O can safely get an organ only from a compatible donor; the doctors check blood group, age and disease status before transplant.

Spot the difference

Rule 1: Biotechnology and crops — Biotechnology includes cytology, biochemistry, molecular biology and genetic engineering, with progress mainly in agriculture and pharmacy. The Government of India set up the National Biotechnology Board in 1982, and it became the Department of Biotechnology in 1986. Hybrid seeds recombine genes of two crops. Genetically modified crops carry a foreign gene. Bt cotton and Bt brinjal carry a gene from the bacterium Bacillus thuringiensis; its toxin kills the bollworm. Golden rice (2005) has a gene for vitamin A and 23 times more beta carotene. Herbicide-tolerant crops allow weeds to be destroyed selectively.

In the figure : In the figure Bt cotton kills the bollworm.

• Easy : Bt cotton makes its own toxin against the bollworm, so less insecticide spraying is needed.
• Medium : Golden rice has 23 times more beta carotene; if normal rice has 1 unit, golden rice has 23 units, which helps prevent vitamin A deficiency.
• Exam-type : Hybrid vs GM: a hybrid recombines genes within crops by crossing; a GM crop gets a gene from another species, such as a bacterium, by genetic engineering.

Rule 2: Biofertilizers and animal husbandry — Biofertilizers such as Rhizobium, Azotobacter, Nostoc, Anabaena and Azolla improve nitrogen fixation and phosphate solubilization. In animal husbandry artificial insemination and embryo transfer improve milk, meat and wool.

• Easy : Rhizobium in the root nodules of pulses fixes nitrogen from the air for the plant.
• Medium : Azolla grows in rice fields and adds nitrogen to the soil, reducing the need for chemical fertilizers.
• Exam-type : Artificial insemination lets semen of one excellent bull fertilise many cows, spreading good milk-yielding genes widely.

Spot the difference

Rule 1: Health biotechnology — Human insulin is now made by bacteria carrying the human insulin gene. Biotechnology gives safer vaccines (antigen made from a pathogen gene). Edible vaccines in transgenic potatoes act against cholera (Vibrio cholerae) and E. coli. Interferon for viral diseases is made by transgenic E. coli. Gene therapy treats genetic disorders in somatic cells, for example PKU.

• Easy : Insulin made by bacteria is the same as human insulin and is safe for diabetics.
• Medium : Matching proteins to diseases: insulin – diabetes; somatostatin – dwarfism; erythropoietin – anaemia; factor VIII – haemophilia; interleukin – cancer; interferon – viral infection.
• Exam-type : An edible vaccine in a potato is cheap and needs no injection, so poor villages could use it more easily.

In the figure : In the figure which protein treats which disease.

Rule 2: Cloning — In reproductive cloning the nucleus of a somatic cell is fused with an enucleated ovum, so no sperm is needed. Dolly the sheep was born in Scotland on 5 July 1996; her nucleus came from the udder cell of a Finn Dorset sheep. Therapeutic cloning gives stem cells.

In the figure : In the figure steps of cloning.

• Easy : Dolly was a clone: she was genetically identical to the sheep that gave the nucleus.
• Medium : Cloning steps: take a somatic cell nucleus, remove the nucleus of an egg, fuse them, let the embryo grow, and place it in a surrogate mother.
• Exam-type : No sperm was used for Dolly; all her genes came from the single nucleus of the udder cell, which is why she was a copy.

Rule 3: Environment and DNA fingerprinting — Microbes treat sewage and solid waste. Bioremediation (जैव उपचार) uses microbes or plants (phyto-remediation): Pseudomonas cleans oil, the fern Pteris vitata absorbs arsenic, Indian mustard absorbs selenium, sunflower absorbs uranium and arsenic, and Deinococcus radiodurans absorbs radiation. Dr Anand Mohan Chakravarti suggested oil-digesting microbes for oil spills. DNA fingerprinting (Center for DNA Fingerprinting and Diagnostics, Hyderabad) identifies criminals and parentage. Bread, cheese, wine, beer, yoghurt and vinegar are the oldest food biotechnology products.

• Easy : Spilled oil at sea can be cleaned by oil-eating Pseudomonas bacteria.
• Medium : Sunflowers planted in contaminated soil absorb uranium and arsenic from it: phytoremediation.
• Exam-type : DNA fingerprinting: the DNA from a child matches half with each parent, so it can settle questions of parentage.

Spot the difference

Rule 1: Three revolutions — Green revolution: methods for maximum yield from minimum land (dwarf varieties of wheat and rice, fertilizers, pesticides, water management); Dr Norman Borlaug (USA) and Dr M. S. Swaminathan (India). White revolution: Dr Verghese Kurien and the cooperative dairy movement of Anand, Gujarat. Blue revolution: production of useful aquatic organisms (rohu, catla, shrimps, lobsters); the "Nil-Kranti Mission 2016" offers 50% to 100% subsidies.

In the figure : In the figure three revolutions in food production.

• Easy : Green revolution = grains; white revolution = milk; blue revolution = fish.
• Medium : Dwarf wheat does not fall over when loaded with heavy grain, so yield is higher.
• Exam-type : Match: Swaminathan – green; Kurien – white; rohu and shrimp – blue.

Rule 2: Fertilizers, pesticides and farming methods — Organic manure improves the water-holding capacity of soil; too much chemical fertilizer reduces fertility. Pesticides such as DDT, malathion and chloropyriphos are poisons that enter the food web and undergo bio-magnification. Hydroponics is soil-less farming. Organic farming completely avoids chemical fertilizers and pesticides. Apiculture: artificial bee boxes allow honey collection without destroying the hive. Medicinal plants such as Adulsa (vasicine, for cough) are cultivated as forests shrink. Fruits are perishable and are processed by drying, salting, airtight packing and making murabba.

• Easy : Compost and cow dung are organic manure; they make soil hold water better.
• Medium : Bio-magnification: a pesticide sprayed on fields reaches small animals, then the birds that eat them, and builds up to dangerous levels at the top of the food chain.
• Exam-type : Mango is processed into murabba or dried slices, which makes a perishable fruit last for months.

Spot the difference