DNA FINGERPRINTING

DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA.

Background

• Almost every cell? in our body contains our DNA?. 
• On average, about 99.9 per cent of the DNA between two humans is the same. 
• The remaining percentage is what makes us unique (unless you are an identical twin!). 
• Although this might sound like a small amount, it means that there are around three million base pairs? that are different between two people. These differences can be compared and used to help distinguish you from someone else.  
• Minisatellites are short sequences (10-60 base pairs long) of repetitive DNA that show greater variation?from one person to the next than other parts of the genome?. This variation is exhibited in the number of repeated units or ‘stutters’ in the minisatellite sequence.
• The first minisatellite was discovered in 1980. 

DNA fingerprinting

• DNA fingerprinting was invented in 1984 by Professor Sir Alec Jeffreys after he realised you could detect variations in human DNA, in the form of these minisatellites. 
• DNA fingerprinting is a technique that simultaneously detects lots of minisatellites in the genome to produce a pattern unique to an individual. This is a DNA fingerprint.
• The probability of having two people with the same DNA fingerprint that are not identical twins is very small. 
• Just like your actual fingerprint, your DNA fingerprint is something you are born with, it is unique to you.

How was the first DNA fingerprint produced?

1. The first step of DNA fingerprinting was to extract DNA from a sample of human material, usually blood.
2. Molecular ‘scissors’, called restrictionenzymes?, were used to cut the DNA. This resulted in thousands of pieces of DNA with a variety of different lengths.
3. These pieces of DNA were then separated according to size by a process called gel electrophoresis?:
   • The DNA was loaded into wells at one end of a porous gel, which acted a bit like a sieve. 
   • An electric current was applied which pulled the negatively-charged DNA through the gel.
   • The shorter pieces of DNA moved through the gel easiest and therefore fastest. It is more difficult for the longer pieces of DNA to move through the gel so they travelled slower. 
   • As a result, by the time the electric current was switched off, the DNA pieces had been separated in order of size. The smallest DNA molecules were furthest away from where the original sample was loaded on to the gel.
4. Once the DNA had been sorted, the pieces of DNA were transferred or ‘blotted’ out of the fragile gel on to a robust piece of nylon membrane and then ‘unzipped’ to produce single strands of DNA. 
5. Next the nylon membrane was incubated with radioactive probes. 
   • Probes are small fragments of minisatellite DNA tagged with radioactive phosphorous.
   • The probes only attach to the pieces of DNA that they arecomplementary? to – in this case they attach to the minisatellites in the genome.
6. The minisatellites that the probes have attached to were then visualised by exposing the nylon membrane to X-ray film. 
   • When exposed to radioactivity a pattern of more than 30 dark bands appeared on the film where the labelled DNA was. This pattern was the DNA fingerprint. 
   • To compare two or more different DNA fingerprints the different DNA samples were run side-by-side on the same electrophoresis gel. 

Illustration showing the steps in DNA fingerprinting. Image credit: Genome Research Limited

DNA profiling 

• Modern-day DNA profiling is also called STR analysis and relies on microsatellites rather than the minisatellites used in DNA fingerprinting.
• Microsatellites, or short tandem repeats (STRs), are the shorter relatives of minisatellites usually two to five base pairs long. Like minisatellites they are repeated many times throughout the human genome, for example ‘TATATATATATA’. 

How is a DNA profile produced today?

1. DNA is extracted from a biological sample. STR analysis is incredibly sensitive so it only needs a tiny amount of someone’s DNA to produce an accurate result. As a result the DNA can be extracted from a wider range of biological samples, including blood, saliva and hair. 
2. Unlike the original DNA fingerprinting method, DNA profiling does not use restriction enzymes to cut the DNA. Instead it uses the polymerase chain reaction (PCR)? to produce many copies of specific STR sequences.
   • PCR is an automated procedure that generates lots of copies of a specific sequence of DNA. It only requires small amounts of DNA to start with and can even make copies from a DNA sample that is partially degraded. 
   • In PCR small bits of DNA calledprimers? bind to complementary sequences of the DNA of interest and mark the starting point for the copying of the DNA of interest. 
   • In STR analysis the primers used in the PCR are designed to attach to either end of the STR sequence of interest. 
   • The primers for each STR is labelled with a specific coloured fluorescent tag. This makes it easier to identify and record the STR sequences after PCR.
3. Once enough copies of the sequence have been produced by PCR, electrophoresis is used to separate the fragments according to size.
4. Each fragment passes by a laser which causes the fragments with fluorescent tags to glow with a specific colour. The output is displayed as a series of coloured peaks (as shown in the image below) highlighting the colour and length of each STR sequence.

Illustration showing the steps in DNA profiling. Image credit: Genome Research Limited

• The more STR sequences that are tested, the more accurate the test is at identifying someone. 
• Other STRs used for forensic purposes are called Y-STRs, which are derived solely from the male Y chromosome?. This is useful for identifying a male perpetrator from mixed DNA samples. 
• Only one person in every 10 million million (10,000,000,000,000) will have a particular STR profile. With the world human population estimated at only 7,100 million (7,100,000,000) it is therefore extremely unlikely you will share the same profile as someone else, unless you are an identical twin. 

Solving crime 

• DNA profiles are very useful in forensics because only a tiny sample of human material left behind after a crime may be sufficient to identify someone. 
• In the UK, a complete DNA profile consists of 11 STR sequences plus a sex determiner to confirm if the profile is from a man or a woman. Now all new profiles include an additional five STR sequences to provide consistency across borders in Europe.
• In the USA, the Federal Bureau of Investigation (FBI) recommends that 13 STR sequences are tested. Many states are increasing the number of STR sequences tested to enable more efficient investigations across state borders. 
• A match made between a crime scene profile and an individual profile identifies a possible suspect. 
• A match made between different crime scene profiles indicates a repeat offender at work.
• The police may use this DNA evidence to support other evidence to help prosecute someone for a crime. Complete DNA profiles give very reliable matches and may provide strong evidence that a suspect is guilty or innocent of a crime.

RESULT OF TEST

SONU   SONGH                  30
NIDHI NARANG                  28
ATUL MOURYA                   28
ANUPAMMA TAKKAR       24
AARZOO BI                          22
AKASH GANGWAR             20

MEIOSIS CELL DIVISION

MEIOSIS
 Meiosis is a process of reductional division in which the number of
chromosomes per cell is cut in half. In animals, meiosis always results in the
formation of gametes, while in other organism it can give rise to spores. The
word “meiosis” comes from greek world meioun, means “to make small”,
since it results in a reduction of the chromosome number.
 The term meiosis was coined by Farmer and Moore (in 1905). The division was
first studied by Van Benedin (1887), Strassburger (1888), Sutton (1900) and
Winiwater (1900). Meiosis I &II were differentiated by Gregoire. In 1911 the
American geneticist Thomas Hunt morgan ( 1866 – 1945) observed cross-over
in Drosophila melanogaster meiosis and provided the first genetic evidence
that genes are transmitted on chromosomes
 Meiosis is essential for sexual reproduction and therefore occurs in all
eukaryotes ( including single –celled organisms) that reproduce sexually.
Meiosis does not occur in archaea or bacteria, which reproduce via asexual
process such as binary fission.
 During meiosis, the genome of diploid germ cell, which is composed of long
segments of DNA packed into chromosomes, undergoes two rounds of
division, resulting in four haploid cells. Each of these cells contain one
complete set of chromosomes, or half of the genetic content of the original
cell. If meiosis produces gametes, these cells must fuse during fertilization to
create a new diploid cell, or zygote before any new growth can occur. Thus
the division mechanism of meiosis is a reciprocal process to the joining of two
genomes that occurs at fertilization. Because the chromosomes of each
parent undergoes enetic recombination during meiosis, each gamete and thus
each zygote, will have a unique genetic blue print encoded in its DNA.
Together meiosis and fertilization constitutes sexually in the eukaryotes, and
generate genetically distinct individuals in population.
 In lower plants, and in many protists, meiosis results in formation of haploid
cells that can divide vegetatively without undergoing fertilization, referred to
as spores. In these groups, gametes are produced by mitosis
 Biochemically, meiosis uses some of the same mechanism employed during
mitosis to accomplish the redistribution of chromosomes. There are several
features unique to meiosis, most importantly the pairing and recombination
between homologous chromosomes, which enable then to separate from
each other.
 The cells of a particular species have a constant number of chromosomes. In
sexually reproducing organisms male and female gametes fuse together to
form the zygote. If the gamete has the same number of chromosomes number
remains constant from generation to generation. This is because of meiotic
division which reduces the chromosome number to half, and counteracts the
effect of fertilization. Thus fertilization and meiosis are compensating events.
Types of meiosis
 The cells in which meiosis takes place are called meiocytes. In animals,
meiocytes are of two types, spermatocytes and oocytes. In higher plants,
meiocytes are differentiated into microsporocytes and megasporocytes.
Depending upon the stage when meiosis occurs, the latter is of three types -
gametic, zygotic and sporic meiosis.
Gametic meiosis
 Meiosis is most of the animal take place during the formation of gametes
(gametogenesis). It is termed as genetic meiosis. When two gametes fuse in
fertilization, a diploid zygote is formed. Gametic meiosis results in diplontic
life cycle
Zygotic meiosis
 In some lower plants meiosis takes place in the zygote and the resulting
organism are haploid. It is called zygotic meiosis. Organism having zygotic
meiosis have haplontic life cycle.
Sporic meiosis
 In plants, meiosis generally occurs at the time of sporogenesis ( formation of
spore or microspores and megaspores) It is called sporic meiosis or
intermediate meiosi. Spores produce a new gametophytic phase in the life
cycle. Gametes are formed by gametophytes. Because of the presence of two
distinct multicelluar phase, diploid and haploid, life cycle of plant is
diplohaplontic .

POLLINATION IN PLANTS

Pollination is process of transfer of pollen grains from the anther to the stigma of a pistil.
- Some external agents help the plants for pollination. Depending on the source of pollen, pollination is 3 types.
a. Autogamy: In this, pollen grains transfer from theanther to the stigma of the same flower.
Complete autogamy is rare in flowers with exposed anthers and stigma. Autogamy in such flowers requires
synchrony in pollen release and stigma receptivity. Also, the anthers and stigma should lie close to each
other to enable self-pollination.Plants like Viola (common pansy), Oxalis & Commelina
produce 2 types of flowers:
 Chasmogamous flowers: They are similar to flowers of other species with exposed anthers and stigma.
 Cleistogamous flowers: They do not open at all. Anthers & stigma lie close to each other. They are
autogamous as there is no chance of cross-pollination.
When anthers dehisce in the flower buds, pollen grains come in contact with the stigma for pollination.
Cleistogamous flowers produce assured seed-set even in the absence of pollinators.
b. Geitonogamy: In this, pollen grains transfer from the anther to the stigma of another flower of the same plant. It is functionally cross-pollination involving a pollinating agent. But it is genetically similar to autogamy since the pollen grains come from the same plant.
c. Xenogamy: In this, pollen grains transfer from anther to the stigma of a different plant. This brings genetically different types of pollen grains to the stigma.
Agents of Pollination
1. Abiotic agents (wind & water) of pollination
Pollination by wind (anemophily):
- More common abiotic agent.
- Ways for effective pollination:
o The flowers produce enormous amount of pollen.
o The pollen grains are light and non-sticky so that they can be transported in wind currents.
o They often possess well-exposed stamens (for easy dispersion of pollens into wind currents).
o Large, feathery stigma to trap air-borne pollen grains.
- Wind pollinated flowers often have a single ovule in each ovary and numerous flowers packed into an inflorescence.
- E.g. Corncob – the tassels are the stigma and style which wave in the wind to trap pollen grains. Wind-pollination is quite common in grasses.
Pollination by water (hydrophily):
- It is quite rare. It is limited to about 30 genera, mostly monocotyledons. E.g. Vallisneria & Hydrilla (fresh
water), Zostera (marine sea-grasses) etc.
- As against this, water is a regular mode of transport for the male gametes among the lower plants. It is believed, particularly for some bryophytes & pteridophytes, that their distribution is limited because of the need for water for the transport of male gametes and fertilisation.
- In Vallisneria, the female flower reaches the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried by water currents and reach the female flowers.
- In sea grasses, female flowers remain submerged in water. Pollen grains are long and ribbon like. They are
carried inside the water and reach the stigma.
- The pollen grains of most of the water-pollinated species have a mucilaginous covering to protect from wetting.
- Not all aquatic plants use hydrophily. In most of aquatic plants (water hyacinth, water lily etc), the flowers emerge above the level of water for entomophily or anemophily.
- Wind and water pollinated flowers are not very colourful and do not produce nectar.
2. Biotic agents (animals) of pollination
- Majority of flowering plants use animals as pollinating agents. E.g. Bees, butterflies, flies, beetles, wasps, ants, moths, birds (sunbirds and humming birds) bats, some primates (lemurs), arboreal (tree-dwelling) rodents, reptiles (gecko lizard & garden lizard) etc.
3 - Pollination by insects (Entomophily), particularly bees is more common.
- Often flowers of animal pollinated plants are specifically adapted for a particular species of animal.
- Features of insect-pollinated flowers:
o Large, colourful, fragrant and rich in nectar. Nectar & pollen grains are the floral rewards for pollination.
o When the flowers are small, they form inflorescence to make them visible.
o The flowers pollinated by flies and beetles secrete foul odours to attract these animals.
o The pollen grains are generally sticky.
- When the animal comes in contact with the anthers and the stigma, its body gets a coating of pollen grains. When it comes in contact with the stigma, it results in pollination.
- Some plants provide safe places as floral reward to lay eggs.
E.g. Amorphophallus (it has the tallest flower of about 6 feet). A species of moth and the plant Yucca cannot
complete their life cycles without each other. The moth deposits its eggs in the locule of the ovary and the flower gets pollinated by the moth. The larvae of the moth come out of the eggs as the seeds start developing.
- Many insects consume pollen or nectar without bringing about pollination. They are called pollen/nectar robbers. Outbreeding Devices:
Majority of flowering plants produces hermaphrodite flowers can undergo self-pollination. Continued selfpollination results in inbreeding depression.
To avoid self pollination and encourage cross-pollination, there are some devices in plants:
a. Avoiding synchronization: In some species, pollen release and stigma receptivity are not synchronized.
Either the pollen is released before the stigma becomes receptive or stigma becomes receptive before the release of pollen. It prevents autogamy.
b. Arrangement of anther & stigma at different positions:
This prevents autogamy.
c. Self-incompatibility: It is a genetic mechanism to prevent self-pollen (from the same flower or other
flowers of the same plant) from fertilization by inhibiting pollen germination or pollen tube growth in the pistil.
d. Production of unisexual flowers: If male & female flowers are present on the same plant (i.e., monoecious,
e.g. castor & maize), it prevents autogamy but not geitonogamy. In dioecious plants (e.g. papaya), male and
female flowers are present on different plants (dioecy). This prevents both autogamy and geitonogamy.
Pollen-pistil Interaction:
- It is a dynamic process involving pollen recognition followed by promotion or inhibition of the pollen.
- This interaction takes place through the chemical components produced by them.
- If the pollen is compatible (right type), the pistil accepts it and promotes post-pollination events. The pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores. The contents of the pollen grain move into the pollen tube. Pollen tube grows through the tissues of the stigma and style and reaches the ovary.
- If the pollen is incompatible (wrong type), the pistil rejects the pollen by preventing pollen germination on
the stigma or the pollen tube growth in the style.
- In some plants, pollen grains are shed at 2-celled condition (a vegetative cell & a generative cell). In such
plants, the generative cell divides and forms the two male gametes during the growth of pollen tube in the stigma.
- In plants which shed pollen in the 3-celled condition, pollen tubes carry 2 male gametes from the beginning.
Pollen tube, after reaching the ovary, enters the ovule through the micropyle and then enters one of the
synergids through the filiform apparatus. The filiform apparatus present at the micropylar part of the synergids
guides the entry of pollen tube.
- A plant breeder can manipulate pollen-pistil interaction, even in incompatible pollinations, to get desired hybrids.
Artificial hybridisation:
- It is one of the major approaches of crop improvement programme.
- In this, desired pollen grains are used for pollination. This is achieved by emasculation & bagging techniques.
- Emasculation is the removal of anthers (using forceps) from the bisexual flower bud of female parent before the anther dehisces.
- Emasculated flowers are covered with a suitable bag (made up of butter paper) to prevent contamination of its stigma with unwanted pollen. This is called bagging.
- When the stigma attains receptivity, mature pollen grains collected from anthers of the male parent are dusted on the stigma. Then the flowers are rebagged and allowed to develop the fruits.
- If the female parent produces unisexual flowers, there is no need for emasculation. The female flower buds are bagged before the flowers open. When the stigma becomes receptive, pollination is carried out using the
desired pollen and the flower rebagged.

FULL FORMS

FULL – FORMS

1.      ABA-absicic acid 2.      ACTH-adrino cartico trophic hormone 3.      ADH-anti diuretic hormone 4.      AIDS-acquired immune deficiency Syndrome  5.      BCG (1999)-bacillus calmelte guarine 6.      C.T.Scan-compuerised tomography 7.      CNS-central nervous system 8.      DAP-diamine phosphate 9.      DBP-distolic blood pressure. 10.  DCT-distal convoluted Tubule 11.  DDT-dichloro diethyl trichloro ethane 12.  DPD(2006)-diffusion pressure deficiency 13.  DPT-diptheria Pertussis tetanus vaccine 14.  ECG (2003)-electrocardiograph 15.  EDTA (1997)-ethlene diamine tetraacetic acid 16.  ELISA-enzyme linked immunosorbent assay 17.  EEG-electroencephalograph 18.  EMP pathway-embden and mayerhoff parnas 19.  ERV(2005)-expiratory reserve volume 20.  ESR-erythrocyte sedimentation rate 21.  ETS-electron transport system 22.  FSH-follicle stimulating hormone 23.  G-6PD-glucose 6 phosphate dehydrogenase 24.  GFR-glomerular filration rate 25.  GHRF-growth hormone releasing factor 26.  HIV-human deficiency hormone 27.  HCG-human chorionic gonadotropin 28.  IAA-Indole acetic acid 29.  IBA-Indole butyric acid 30.  IUD-intra-utirine divices 31.  ICSH- Interstitial cell stimulating hormone (LH) 32.  IPM- Integrated pest management 33.  IUCD- Intra uterine contraceptive device 34.  IVF- in vitro fertilization 35. AMP-adinosine  monophosphate

1.      LH- Leutinizing hormone 2.      LTH- Lactotrophic hormone( Prolactin) 3.      MDR-TB - Multi-drug-resistant tuberculosis 4.      MET – Mass emission tomography 5.      MRI – Magnetic resonance imaging 6.      MSH –Melanocytes stimulating hormone 7.      NAA – Napthalene acetic acid 8.      NADP (2002) – Nicotinamide dinucleotide phosphate 9.      NCCP – National cholera control program 10.  NFCP –National Filaria control program 11.  NLCP – National leprosy control program 12.  NMEP – National malaria eradication program 13.  NSEP – National                  eradication program 14.  OP(2007) -  Osmotic pressure 15.  PEM – Protein energy maltnutrition 16.  PEP – Phosphoenol Pyruvic acid 17.  PGA – Phosphoglyceric acid 18.  PGAL - Phosphoglyceraldehyde 19.  PCR – Ploymerase Chain Reaction 20.  PQ - Plastoquinone 21.  P-RH –Prolactin releasing hormone 22.  PRL - Physical Research Laboratory 23.  RAAS – Renin angiotensin aldosterone system 24.  RAS – Renin angiotensin system 25.  RBC – Red Blood Corpuscles 26.  RUBISCO – Ribulose phosphate carboxylase oxygenase 27.  RuBP- Ribulose 1,5 bisphosphate 28.  SAN(2004) – Sino atrial node 29.  SCID – Severe combined immune defficieny 30.  SDP – Short day plants 31.  STH – Somato trophic hormone 32.  TCT - Thyrocalcitonin 33.  VD – Veneral diseases 34.  WBC -  White blood corpuscles