Biotechnosium...

DNA

DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).

The information in DNA is stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T). Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences.

DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule. Together, a base, sugar, and phosphate are called a nucleotide. Nucleotides are arranged in two long strands that form a spiral called a double helix. The structure of the double helix is somewhat like a ladder, with the base pairs forming the ladder’s rungs and the sugar and phosphate molecules forming the vertical sidepieces of the ladder.

An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell.


DNA is a double helix formed by base pairs attached to a sugar-phosphate backbone.

DNA Sequencing

DNA sequencing encompasses biochemical methods for determining the order of the nucleotide bases, adenine, guanine, cytosine, and thymine, in a DNA oligonucleotide. The sequence of DNA constitutes the heritable genetic information in nuclei, plasmids, mitochondria, and chloroplasts that forms the basis for the developmental programs of all living organisms. Determining the DNA sequence is therefore useful in basic research studying fundamental biological processes, as well as in applied fields such as diagnostic or forensic research. The advent of DNA sequencing has significantly accelerated biological research and discovery. The rapid speed of sequencing attainable with modern DNA sequencing technology has been instrumental in the large-scale sequencing of the human genome, in the Human Genome Project. Related projects, often by scientific collaboration across continents, have generated the complete DNA sequences of many animal, plant, and microbial genomes.




Maxam-Gilbert sequencing


In 1976-1977, Allan Maxam and Walter Gilbert developed a DNA sequencing method based on chemical modification of DNA and subsequent cleavage at specific bases . Although Maxam and Gilbert published their chemical sequencing method two years after the ground-breaking paper of Sanger and Coulson on plus-minus sequencing, Maxam-Gilbert sequencing rapidly became more popular, since purified DNA could be used directly, while the initial Sanger method required that each read start be cloned for production of single-stranded DNA. However, with the development and improvement of the chain-termination method (see below), Maxam-Gilbert sequencing has fallen out of favour due to its technical complexity, extensive use of hazardous chemicals, and difficulties with scale-up. In addition, unlike the chain-termination method, chemicals used in the Maxam-Gilbert method cannot easily be customized for use in a standard molecular biology kit.

In brief, the method requires radioactive labelling at one end and purification of the DNA fragment to be sequenced. Chemical treatment generates breaks at a small proportion of one or two of the four nucleotide bases in each of four reactions (G, A+G, C, C+T). Thus a series of labelled fragments is generated, from the radiolabelled end to the first 'cut' site in each molecule. The fragments are then size-separated by gel electrophoresis, with the four reactions arranged side by side. To visualize the fragments generated in each reaction, the gel is exposed to X-ray film for autoradiography, yielding an image of a series of dark 'bands' corresponding to the radiolabelled DNA fragments, from which the sequence may be inferred.

Also sometimes known as 'chemical sequencing', this method originated in the study of DNA-protein interactions (footprinting), nucleic acid structure and epigenetic modifications to DNA, and within these it still has important applications.

Chain-termination methods


While the chemical sequencing method of Maxam and Gilbert, and the plus-minus method of Sanger and Coulson were orders of magnitude faster than previous methods, the chain-terminator method developed by Sanger was even more efficient, and rapidly became the method of choice. The Maxam-Gilbert technique requires the use of highly toxic chemicals, and large amounts of radiolabeled DNA, whereas the chain-terminator method uses fewer toxic chemicals and lower amounts of radioactivity. The key principle of the Sanger method was the use of dideoxynucleotides triphosphates (ddNTPs) as DNA chain terminators.

The classical chain-termination or Sanger method requires a single-stranded DNA template, a DNA primer, a DNA polymerase, radioactively or fluorescently labeled nucleotides, and modified nucleotides that terminate DNA strand elongation. The DNA sample is divided into four separate sequencing reactions, containing the four standard deoxynucleotides (dATP, dGTP, dCTP and dTTP) and the DNA polymerase. To each reaction is added only one of the four dideoxynucleotides (ddATP, ddGTP, ddCTP, or ddTTP). These dideoxynucleotides are the chain-terminating nucleotides, lacking a 3'-OH group required for the formation of a phosphodiester bond between two nucleotides during DNA strand elongation. Incorporation of a dideoxynucleotide into the nascent (elongating) DNA strand therefore terminates DNA strand extension, resulting in various DNA fragments of varying length. The dideoxynucleotides are added at lower concentration than the standard deoxynucleotides to allow strand elongation sufficient for sequence analysis.

The newly synthesized and labeled DNA fragments are heat denatured, and separated by size (with a resolution of just one nucleotide) by gel electrophoresis on a denaturing polyacrylamide-urea gel. Each of the four DNA synthesis reactions is run in one of four individual lanes (lanes A, T, G, C); the DNA bands are then visualized by autoradiography or UV light, and the DNA sequence can be directly read off the X-ray film or gel image. In the image on the right, X-ray film was exposed to the gel, and the dark bands correspond to DNA fragments of different lengths. A dark band in a lane indicates a DNA fragment that is the result of chain termination after incorporation of a dideoxynucleotide (ddATP, ddGTP, ddCTP, or ddTTP). The terminal nucleotide base can be identified according to which dideoxynucleotide was added in the reaction giving that band. The relative positions of the different bands among the four lanes are then used to read (from bottom to top) the DNA sequence as indicated.



There are some technical variations of chain-termination sequencing. In one method, the DNA fragments are tagged with nucleotides containing radioactive phosphorus for radiolabelling. Alternatively, a primer labeled at the 5’ end with a fluorescent dye is used for the tagging. Four separate reactions are still required, but DNA fragments with dye labels can be read using an optical system, facilitating faster and more economical analysis and automation. This approach is known as 'dye-primer sequencing'. The later development by L Hood and coworkers] of fluorescently labeled ddNTPs and primers set the stage for automated, high-throughput DNA sequencing.



The different chain-termination methods have greatly simplified the amount of work and planning needed for DNA sequencing. For example, the chain-termination-based "Sequenase" kit from USB Biochemicals contains most of the reagents needed for sequencing, prealiquoted and ready to use. Some sequencing problems can occur with the Sanger Method, such as non-specific binding of the primer to the DNA, affecting accurate read out of the DNA sequence. In addition, secondary structures within the DNA template, or contaminating RNA randomly priming at the DNA template can also affect the fidelity of the obtained sequence. Other contaminants affecting the reaction may consist of extraneous DNA or inhibitors of the DNA polymerase.

Dye-terminator sequencing




An alternative to primer labelling is labelling of the chain terminators, a method commonly called 'dye-terminator sequencing'. The major advantage of this method is that the sequencing can be performed in a single reaction, rather than four reactions as in the labelled-primer method. In dye-terminator sequencing, each of the four dideoxynucleotide chain terminators is labelled with a different fluorescent dye, each fluorescing at a different wavelength. This method is attractive because of its greater expediency and speed and is now the mainstay in automated sequencing with computer-controlled sequence analyzers (see below). Its potential limitations include dye effects due to differences in the incorporation of the dye-labelled chain terminators into the DNA fragment, resulting in unequal peak heights and shapes in the electronic DNA sequence trace chromatogram after capillary electrophoresis (see figure to the right). This problem has largely been overcome with the introduction of new DNA polymerase enzyme systems and dyes that minimize incorporation variability, as well as methods for eliminating "dye blobs", caused by certain chemical characteristics of the dyes that can result in artifacts in DNA sequence traces. The dye-terminator sequencing method, along with automated high-throughput DNA sequence analyzers, is now being used for the vast majority of sequencing projects, as it is both easier to perform and lower in cost than most previous sequencing methods.

Links for people interested in DNA-related software and bioinformatics:

Art Roberts's informative web site on biotechnology

The IUBio Archive for Biology data and software

The BioCatalog at EBI

Genamics (MolBiol software database)

UK HGMP Resource Centre (bioinfo services after registration)

TIGR software tools for genomics

STADEN package - PreGAP4 and GAP4 for Contig (pre)assembly

Some things on/for ACeDB

EST-related links and software/web tools

A QTL-analysis software package

Following is the list of Colleges offering B.Pharmacy degree in Andhra Pradesh. I have here provide the addresses along with the number of seats available in the respective colleges.

All the below colleges have 60 seats. When there is a variation its(no of seats) mentioned

Hyderabad District:

1. Anwar-Ui-Uloom College of Pharmacy; New Mallepally, Hyderabad. (60 seats)
2. Deccon college of Pahrmacy; Kanchanbagh, Zafargarh (P), Hyderabad. (40 seats)
3. Gokaraju Rangaraju College of Pharmacy; Bachupally, Kukatpally, Hyderabad (60 seats)
4. G.Pulla Reddy College of Pharmacy; Mehdipatnam, Hyderabad. (60 seats)
5. M.E.S.C.O. Collegte of Pharmacy; Mustaidipura, Karwan Road, Hyderabad-500006 (30 seats)
6. RBVRR Women's College of Pharmacy; BarkatPur, Hyderabad. (60 seats)
7. RGR Siddanti College of Pharmacy; 703, Bolton Road, Opp. Tiwil Gardens, Behind Parade Grounds, Near JBs, Secunderabad. (60 seats).
8. Shadan College of Pharmacy; Peerancheru, Near Kali Temple, Himayat sagar road, Hyderabad. (60 seats)
9. Shadan Women's College of Pharmacy; Rajbhavan Road, Kairatabad, Hyderabad. (60 seats)
10. Sarojini Naidu Vanitha Pharmacy Maha Vidyalaya; Mukarramjahi road, Nampally, Hyderabad. (60 seats)
11. Sri Ventkateshwara College of Pharmacy; Hi-Tech city road, Vittalrao nagar, Madhapur, Hyderabad. (60 seats).
12. Sultan-Ui-Uloom College of Pharmacy; Road No:3, Banjara hills, Mount Pleasant, Hyderabad. (60 seats)
13. Teegala Ram Reddy College of Pharmacy; Sarror nagar, Meerpet, Hyderabad. (60 seats)

1. Azad College of Pharmacy; Moinabad, Rangareddy District. (60 seats)
2. Bharat College of Pharmacy; Mangalpally(Vil), Ibrahimp[atnam, R.R district. (60 seats)
3. CMR College of Pharmacy; Kandlakoya (V), Medchal Road, R.R.District. (60 seats)
4. Gurunanak Institute of Pharmacy; Ibrahim patnam, R.R.Dist. (60 seats)
5. Holy Mary Institute of Technology and Science College of Pharmacy; Bogaram(V), Keesara(M), R.R Dist. (60 seats)
6. J.J. College of Pharmacy; Maheshwaram, R.R.Dist. (60 seats)
7. Lalitha College of Pharmacy; Venkatapur(V), Ghatkesar (M), R.R.Dist. (60 seats)
8. Malla Reddy College of Pharmacy; Dhulapally Post, Via Hakimpet, Secunderabad, R.R.Dist. (60 seats)
9. Malla Reddy Institute of Pharmacy Sciences; Mysammaguda, Dhulapally Post, Via Hakimpet, Secunderabad, R.R.Dist. (60 seats)
10. Mother Theresa College of Pharmacy; NFC Nagar, Ghateskar (M), R.R Dist. (60 seats)
11. Priya Darshini College of Pharmaceutical Sciences; Narapally Main Road, Chowdaryguda (V), Ghatkesar(M), R.R.Dist. (60 seats)
12. Sree Datha Institute of Pharmacy; Sheriguda(V), Ibrahimpatnam(M), R.R.Dist. (60 seats)
13. Sri Indhu Institute of Pharmacy; Sheriguda(V), Ibrahimpatnam(M), R.R.Dist. (60 seats)
14. Samskruti College of Pharmacy; Kondapur, Ghatkesar (M), R.R.Dist. (60 seats)
15. Vijaya College of Pharmacy; Munuganur, Hayat Nagar, R.R.Dist. (60 seats)

1. MNR College of Pharmacy; Fasalwadi(V), Narsapur road, Sangareddy, Medak District. (60 seats)
2. Sri Krupa Institute of Pharmaceutical Sciences; Velkatta(V), Kondapak(M), Siddpet Road, Medak District. (60 seats)

1. Madhira Institue of Pharmaceutical Sciences; Madhiranagar, Chilkur, Nalgonda District. (60 seats)
2. Nalanda College of Pharmacy; Cherlapally, Nalgonda District. (60 seats)
3. Nizam Institute of Pharmacy; Deshmukhi(V), Pochampally(M), Near Ramoji Film City, Nalgonda Dist. (60 seats)
4. Vathsalya College of Pharmacy;Bhongir, Nalgonda District. (60 seats)
5. Vignan Institute of Pharmaceutical Sciences; Vignan Hills, Near Ramoji Film City, Nalgonda Dist.
6. Vikas College of Pharmacy; Rayanigudem(V), Near NH-9, Surya pet, Nalgonda Dist. (60 seats)

1. University College of Pharmaceutical Sciences; Kakatiya University, Warangal Dist. (50 seats)
2. Aurobindo College of Pharmaceutical Sciences; Gangadevapally, geesukonda, Narsampet Road, Warangal District. (60 seats)
3. Balaji Institute of Pharmaceutical Sciences; Lankeypally(V), Maheswaram(PO), Narsampet(M), Warangal Dist. (60 seats)
4. Blue Birds College of Pharmacy; Near Chintagutta Camp, Bheemavaram(V), Hanmakonda, Warangal Dist. (45 seats)
5. Care College of Pharmacy; Oglapur(V), Atmakur(M), Warangal Dist. (60 seats)
6. Janagaon Institute of Pharmaceutical Sciences; Yeshwanthpur(V), Janagoan(M), Warangal Dist. (60 seats)
7. Jayamukhi College of Pharmacy; Moqudumpur(V), Narsampet(PO), Chinarao pet(M), Warangal Dist. (60 seats)
8. 7. Netaji Institute of Pharmaceutical Sciences; Sommidi, Hanmakonda, Warangal Dist. (60 seats)
9. 8. SR College of Pharmacy; Anantha Nagar(V), Hasanparthy(M), Warangal Dist. (60 seats)
10. Sri Shivani College of Pharmacy; Mulugu road, Warangal Dist. (60 seats)
11. St. John's College of Pharmacy; Yellapur(V), Hasanparthy(M), Warangal Dist. (60 seats)
12. St. Peters Institute of Pharmaceutical Sciences; Vidyanagar, Hanmakonda, Warangal Dist. (60 seats)
13. Thalla Padmavathi College of Pharmacy; Kareemabad, Warangal Dist. (60 seats)
14. Vaagdevi College of Pharmacy; Ramnagar, Hanmakonda, Warangal Dist. (60 seats)
15. Vikas College of Pharmacy; Vikas Nagar, Shameerpet(V), Janagaon(M), Warangal Dist. (60 seats)

1. SMT.Sarojini Ramulamma College of Pharmacy; Seshadri nagar, Mahaboobnagarnagar Dist (60 seats).
2. Kottam Institute of Pharmacy; Erravaly X Roads, Itikyal(M), Mahaboobnagar Dist (60 seats).

1. SRR College of Pharmaceutical Sciences; Valbhapur(V), Elkathurthy(M), Karimnagar Dist. (60 seats).
2. Trinity College of Pharmaceutical Sciences; Pragathi nagar, Peddapalli, Karimnagar Dist (60 seats).
3. Vaageshwari College of Pharmacy; Ramakrishnan colony, Thimmapur(M), Karimnagar dist (60 seats).

1. Brown's College of Pharmacy; Ammapelam, Near Thanikella, Konijerla(M), Khammam Dist.
2. KLR College of Pharmacy; Contractor Colony, Palavancha, Khammam Dist.

1. Andhra University College of Pharmacy; Waltair, Vishakapatnam Dist. (40 seats)
2. GITAM College of Pharmacy; Ghandi Nagar Campus, Rushikonda, Vishakapatnam Dist.
3. Vignan Institute of Pharmacy; Jaggarajupet, Gajuwaka, Beside VSEZ.
4. Yalamachily Institute of Pharmaceutical Sciences; Yalamarty, Tharluwada, Vishakapatnam.

1. K.V.S.R. Siddartha College of Pharmaceutical Sciences; Pinnamaneni Poly clinic Road, Siddartha Nagar, Vijayawada.
2. Sri Siddartha Pharmacy College; Ammavari Thota, Nuzividu, Krishna District.
3. Vikas College of Pharmacy; Puturala Road, Vissannapet, Krishna district.

1. A.M.Reddy Memorial College of Pharmacy; AMR Nagar, Petlutivaripalem, Narsaraopet(M), Guntur Dist.
2. ASN College of Pharmacy; Burripalem Road, Nelapadu, Tenali, Guntur dist.
3. Bapatla College of Pharmacy; Bapatla, Guntur Dist.
4. Chalapthi Institute of Pharmaceutical Sciences; Chalapathi Nagar, LAM, Guntur.
5. Don Bosco PG College; 5th Mile, Pulladigunta, Komepadu(V), Vatticheru, Guntur Dist. (45 seats)
6. Hindu College of Pharmacy; Koritepadu(V), Amaravathi, Guntur Dist.
7. Nagarjuna Institute of Pharmaceutical Sciences; Opp.JKC College Road, Guntur.
8. Nirmala College of Pharmacy; Atmakur, Mangalagiri, Guntur Dist.
9. Siddartha College of Pharmacy; Siddartha Nagar, Kantepudi(V), Sattenapalli(M), Guntur Dist.
10. Southern Institute of Medical Science College of Pharmacy; Mangaladas Nagar, Guntur.
11. Vagdevi College of Pharmacy; Gurajala, Guntur Dist.
12. Vignan College of Pharmacy; Vadalamudi, Guntur.
13. Victoria College of Pharmacy; Ankireddy Palem Guntur Dist.
14. Viswa Bharathi College of Pharmaceutical Sciences; Pericherla, NTR Road, Guntur Dist.

1. Aditya Institute of Pharmaceutical Science & Research; ADB road, Surapalem, Peddapuram, East Godavari District.
2. GIET School of Pharmacy; NH-5, Chaitanya Nagar, Rajahmundry, E.G.Dist.
3. Sri Aditya Institute of Pharmaceutical Science & Research; ADB road, Surapalem, Peddapuram, East Godavari District.
4. St.Mary's College of Pharmaceutical Sciences; Surampalem, ADB Road, Peddapuram, EG.Dist.

1. AKRG College of Pharmacy; Nallajerla, Near Tadepallygudem, W.G.Dist.
2. Nova College of Pharmacy; Vengavaram, Jangareddy Gudem(M), W.G.Dist.
3. Sri Vaasavi Institute of Pharmaceutical Science; Tadepallygudem, W.G.Dist.
4. Sri Vishnu College of Pharmacy; Vishnupur, Bhimavaram, W.G.Dist.

1. Avanthi College of Pharmaceutical Sciences; Cherukupalli, Bhogapuram, Vijayanagaram Dist.
2. Maharaja College of Pharmacy; Phoolbagh, Vijayanagaram Dist.

1. Sri Venkateshwara College of Pharmacy; Etcherla, Srikakulam Dist.

1. Maleneni Lakshmaiah College of Pharmacy; Kanumella(V), Singarayakonda, Prakasham District.
2. Samuel Goerge Institute of Pharmaceutical Sciences; Markapuram, Prakasham Dist.
3. QIS College of Pharmacy; Vengamukkapalem, Prakasham Dist.

1. SAFA College of Pharmacy; B.Tendrapadu, Nandyal Road, Kurnool Dist. (45 seats)

1. Sri Padmavathi Mahila Viswa Vidyalayam College of Pharmacy; Tirupathi. (40 seats)
2. Sri Krishna Chaitanya College of Pharmacy; Gangannagaripally(V), Nimmanapalli, Road, Basinikonda Panchayat, Madanapalle, Chittoor Dist.
3. Sree Vidyaniketan College of Pharmacy; Sree Sainath Nagar, A.Rangampet, Chandragiri(M), Chittoor Dist.
4. Sri Lakshmi Narasimha College of Pharmacy; Gollamadugu, Palluru(Po), Gudipala(M), Chittoor Dist.
5. Sri Padmavathi School of Pharmacy; Vaishanvi Nagar, Tiruchanoor(Po), Tirupathi.

1. Balaji College of Pharmacy; Balaji Educational Society, Near RTC Bus Stand, Khaja Nagar, Ananthapur Dist.
2. Raghavendra Institute of Pharmaceutical Education & Research; Saigram, Krishna Reddy Palli Cross, Chiyyedu(Po), Ananthapur Dist.

1. Jagan's College of Pharmacy; Jangala Kandriga, Nellore Dist.
2. Rao's College of Pharmacy; Veranna Kanpur Bit - I, Venkatachalam(M), Nellore DIst.
3. Vagdevi College of Pharmacy & Research Centre; Brahmadevam(V), Nellore Dist.

1. Annamacharya College of Pharmacy; New Bownepally, Rajampet Town, Cuddapah Dist.
2. Nirmala College of Pharmacy; Putlampalli(V), Madras Road, Near Pratap Public school, Buddayapalli(P), Cuddapah Dist.
3. Sri P.Ramireddy Memorial College of Pharmacy; Prakruthi Nagar, Utukur, Cuddapah Dist.

Tissue engineering is the use of a combination of cells within an artificially-created support system (e.g. an artificial pancreas or a bioartificial liver. The term treatments">regenerative medicine is often used synonymously with tissue engineering, although those involved in regenerative medicine place more emphasis on the use of stem cells to produce tissues.

In 2003, the NSF published a report entitled "The Emergence of Tissue Engineering as a Research Field" [1], which gives a thorough description of the history of this field.

Micromass cultures of C3H-10T1/2 cells at varied oxygen tensions stained with A commonly applied definition of tissue engineering, as stated by Langer and Vacanti, is "an interdisciplinaryfield that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve function or a whole organ". ^{Tissue engineering has also been defined as "understanding the principles of tissue growth, and applying this to produce functional replacement tissue for clinical use."citation needed]}

^{Powerful developments in the multidisciplinary field of tissue engineering have yielded a novel set of tissue replacement parts and implementation strategies. Scientific advances in biomaterials, stem cells, growth and differentiation factors, and biomimetic environments have created unique opportunities to fabricate tissues in the laboratory from combinations of engineered extracellular matrices ("scaffolds"), cells, and biologically active molecules. Among the major challenges now facing tissue engineering is the need for more complex functionality, as well as both functional and biomechanical stability in laboratory-grown tissues destined for transplantation. The continued success of tissue engineering, and the eventual development of true human replacement parts, will grow from the convergence of engineering and basic research advances in tissue, matrix, growth factor, stem cell, and developmental biology, as well as materials science and bioinformatics.}

The term cloning is used by scientists to describe many different processes that involve making duplicates of biological material. In most cases, isolated genes or cells are duplicated for scientific study, and no new animal results. The experiment that led to the cloning of Dolly the sheep in 1997 was different: It used a cloning technique called somatic cell nuclear transfer and resulted in an animal that was a genetic twin -- although delayed in time -- of an adult sheep. This technique can also be used to produce an embryo from which cells called embryonic stem (ES) cells could be extracted to use in research into potential therapies for a wide variety of diseases.

Thus, in the past five years, much of the scientific and ethical debate about somatic cell nuclear transfer has focused on its two potential applications: 1) for reproductive purposes, i.e., to produce a child, or 2) for producing a source of ES cells for research.

Cloning for Reproductive Purposes

The technique of transferring a nucleus from a somatic cell into an egg that produced Dolly was an extension of experiments that had been ongoing for over 40 years. In the simplest terms, the technique used to produce Dolly the sheep - somatic cell nuclear transplantation cloning - involves removing the nucleus of an egg and replacing it with the diploid nucleus of a somatic cell. Unlike sexual reproduction, during which a new organism is formed when the genetic material of the egg and sperm fuse, in nuclear transplantation cloning there is a single genetic "parent." This technique also differs from previous cloning techniques because it does not involve an existing embryo. Dolly is different because she is not genetically unique; when born she was genetically identical to an existing six-year-old ewe. Although the birth of Dolly was lauded as a success, in fact, the procedure has not been perfected and it is not yet clear whether Dolly will remain healthy or whether she is already experiencing subtle problems that might lead to serious diseases. Thus, the prospect of applying this technique in humans is troubling for scientific and safety reasons in addition to a variety of ethical reasons related to our ideas about the natural ordering of family and successive generations.

Scientific Uncertainties

Several important concerns remain about the science and safety of nuclear transfer cloning using adult cells as the source of nuclei. To date, five mammalian species -- sheep, cattle, pigs, goats, and mice -- have been used extensively in reproductive cloning studies. Data from these experiments illustrate the problems involved. Typically, very few cloning attempts are successful. Many cloned animals die in utero, even at late stages or soon after birth, and those that survive frequently exhibit severe birth defects. In addition, female animals carrying cloned fetuses may face serious risks, including death from cloning-related complications.

An additional concern focuses on whether cellular aging will affect the ability of somatic cell nuclei to program normal development. As somatic cells divide they progressively age, and there is normally a defined number of cell divisions that can occur before senescence. Thus, the health effects for the resulting liveborn, having been created with an "aged" nucleus, are unknown. Recently it was reported that Dolly has arthritis, although it is not yet clear whether the five-and-a-half-year-old sheep is suffering from the condition as a result of the cloning process. And, scientists in Tokyo have shown that cloned mice die significantly earlier than those that are naturally conceived, raising an additional concern that the mutations that accumulate in somatic cells might affect nuclear transfer efficiency and lead to cancer and other diseases in offspring. Researchers working with clones of a Holstein cow say genetic programming errors may explain why so many cloned animals die, either as fetuses or newborns.

Ethical Concerns

The announcement of Dolly sparked widespread speculation about a human child being created using somatic cell nuclear transfer. Much of the perceived fear that greeted this announcement centered on the misperception that a child or many children could be produced who would be identical to an already existing person. This fear is based on the idea of "genetic determinism" -- that genes alone determine all aspects of an individual -- and reflects the belief that a person's genes bear a simple relationship to the physical and psychological traits that compose that individual. Although genes play an essential role in the formation of physical and behavioral characteristics, each individual is, in fact, the result of a complex interaction between his or her genes and the environment within which he or she develops. Nonetheless, many of the concerns about cloning have focused on issues related to "playing God," interfering with the natural order of life, and somehow robbing a future individual of the right to a unique identity.

Policy and Regulation

Several groups have concluded that reproductive cloning of human beings creates ethical and scientific risks that society should not tolerate. In 1997, the National Bioethics Advisory Commission recommended that it was morally unacceptable to attempt to create a child using somatic cell nuclear transfer cloning and suggested that a moratorium be imposed until safety of this technique could be assessed. The commission also cautioned against preempting the use of cloning technology for purposes unrelated to producing a liveborn child.

Similarly, in 2001 the National Academy of Sciences issued a report stating that the United States should ban human reproductive cloning aimed at creating a child because experience with reproductive cloning in animals suggests that the process would be dangerous for the woman, the fetus, and the newborn, and would likely fail. The report recommended that the proposed ban on human cloning should be reviewed within five years, but that it should be reconsidered "only if a new scientific review indicates that the procedures are likely to be safe and effective, and if a broad national dialogue on societal, religious and ethical issues suggests that reconsideration is warranted." The panel concluded that the scientific and medical considerations that justify a ban on human reproductive cloning at this time do not apply to nuclear transplantation to produce stem cells. Several other scientific and medical groups also have stated their opposition to the use of cloning for the purpose of producing a child.

Cloning for the Isolation of Human ES Cells

The cloning debate was reopened with a new twist late in 1998, when two scientific reports were published regarding the successful isolation of human stem cells. Stem cells are unique and essential cells found in animals that are capable of continually reproducing themselves and renewing tissue throughout an individual organism's life. ES cells are the most versatile of all stem cells because they are less differentiated, or committed, to a particular function than adult stem cells. These cells have offered hope of new cures to debilitating and even fatal illness. Recent studies in mice and other animals have shown that ES cells can reduce symptoms of Parkinson's disease in mouse models, and work in other animal models and disease areas seems promising.

In the 1998 reports, ES cells were derived from in vitro embryos six to seven days old destined to be discarded by couples undergoing infertility treatments, and embryonic germ (EG) cells were obtained from cadaveric fetal tissue following elective abortion. A third report, appearing in the New York Times, claimed that a Massachusetts biotechnology company had fused a human cell with an enucleated cow egg, creating a hybrid clone that failed to progress beyond an early stage of development. This announcement served as a reminder that ES cells also could be derived from embryos created through somatic cell nuclear transfer, or cloning. In fact, several scientists believed that deriving ES cells in this manner is the most promising approach to developing treatments because the condition of in vitro fertilization (IVF) embryos stored over time is questionable and this type of cloning could overcome graft-host responses if resulting therapies were developed from the recipient's own DNA.

Ethical Concerns

For those who believe that the embryo has the moral status of a person from the moment of conception, research or any other activity that would destroy it is wrong. For those who believe the human embryo deserves some measure of respect, but disagree that the respect due should equal that given to a fully formed human, it could be considered immoral not to use embryos that would otherwise be destroyed to develop potential cures for disease affecting millions of people. An additional concern related to public policy is whether federal funds should be used for research that some Americans find unethical.

Policy and Regulation

Since 1996, Congress has prohibited researchers from using federal funds for human embryo research. In 1999, DHHS announced that it intended to fund research on human ES cells derived from embryos remaining after infertility treatments. This decision was based on an interpretation "that human embryonic stem cells are not a human embryo within the statutory definition" because "the cells do not have the capacity to develop into a human being even if transferred to the uterus, thus their destruction in the course of research would not constitute the destruction of an embryo." DHHS did not intend to fund research using stem cells derived from embryos created through cloning, although such efforts would be legal in the private sector.

In July 2001, the House of Representatives voted 265 to 162 to make any human cloning a criminal offense, including cloning to create an embryo for derivation of stem cells rather than to produce a child. In August 2002, President Bush, contending with a DHHS decision made during the Clinton administration, stated in a prime-time television address that federal support would be provided for research using a limited number of stem cell colonies already in existence (derived from leftover IVF embryos). Current bills before Congress would ban all forms of cloning outright, prohibit cloning for reproductive purposes, and impose a moratorium on cloning to derive stem cells for research, or prohibit cloning for reproductive purposes while allowing cloning for therapeutic purposes to go forward. As of late June, the Senate has taken no action. President Bush's Bioethics Council is expected to recommend the prohibition of reproductive cloning and a moratorium on therapeutic cloning later this summer.

Scientists have created nearly a dozen new lines of human embryonic stem (ES) cells that for the first time carry the genetic signature of diseased or injured patients. The breakthrough represents a dramatic increase in the efficiency of creating such lines and may eventually pave the way for treating conditions such as spinal cord injury with stem cell transplants.

Eggs-perts. Through practice with cow eggs (above) and other means, Korean researchers have increased their efficiency at cloning human embryos to create stem cells (inset). CREDIT: Lee Jin-man/AP; (inset) Hwang et al.

Last year, a group led by veterinarian Woo Suk Hwang and gynecologist Shin Yong Moon at Seoul National University reported the first derivation of ES cells from human nuclear transfer Science --a process that involves replacing an oocyte's nucleus with one from a different cell, and then chemically kick-starting development of the egg. But those efforts yielded just one cell line from more than 200 tries.

Hwang cautions that his team remains years away from transplanting the cells into people. "We have to be over-convinced" that the cells are safe, he says. However, the cell line derived from the diabetes patient should be of great interest to scientists.

"The possibility of being able to study disease in a culture dish is very exciting," says Douglas Melton, who has recently received permission from a university ethics committee to derive ES cells from diabetes patients in his laboratory at Harvard. "For the first time, we will have a chance to study the root causes of the disease."

The new results may also influence the ongoing political debate over whether research with human embryonic stem cells, cloned or not, is ethically justified. "Some people will hate it, others will love it," says Rudolf Jaenisch of the Massachusetts Institute of Technology. "But it puts the discussion on a very firm footing now. People will have to rethink the argument that it's not efficient."