__________CT________________________
1) virus MCQ 19 for CT
Comment: A RNA virus does not have to be a retrovirus e.g. influenze but a retrovirus definitely will have RNA as its genetic material.
Why not C? I think C is a poor choice. Because it is talking about bacteriophage (lysogenic) when the question is making reference to an animal virus i.e. herpes(latent) so it doesn't tell me anything about the herpes virus because it is irrelevant. Also, the teaches argued that when given a choice, an omission is always a poorer option.
___________Cloning________
2) http://www.dnalc.org/ddnalc/resources/pcr.html
If you have trouble visualising how PCR can lead to the amplification of a specific DNA segment, this is a good site.
3)Commercially, the insulin chains are produced separately but are fused with the beta-galactosidase. Cyanogen bromide is needed to first cleave the beta-galactosidase so that you can get pure chain A and chain B before The two chains are subjected to oxidation for the formation of disulphide bonds between them.
________Plant Cloning_________
b) Why is sulphur needed for nucleic acid synthesis? Or just simply plant growth?
There are many minerals needed for good plant growth but we do not know exactly the roles they play.
It is intuitive to think of the importance of nitrogen and phosphorous but what about potassium and sulphur in notes? Here is something for you:
Sulphur
Both the yield and quality of crops grown on sulphur-deficient soils are reduced unless sulphur is included in the fertilizer treatment. Sulphur fertilizer can increase crop yields and quality and result in significant economic returns to producers. Sulphur fertilization also improves overall fertilizer efficiency.
(http://www.sulphurinstitute.org/learnmore/faq.cfm#plants)
Potassium
Potassium is the only essential plant nutrient that is not a constituent of any
plant part. Potassium is a key nutrient in the plants tolerance to stresses such as cold/hot
temperatures, drought, wear and pest problems. Potassium acts as catalysts for many of
the enzymatic processes in the plant that are necessary for plant growth to take place.
Another key role of potassium is the regulation of water use in the plant
(osmoregulation). This osmoregulation process affects water transport in the xylem,
maintains high daily cell turgor pressure which affects wear tolerance, affects cell
elongation for growth and most importantly it regulates the opening and closing of the
stomates which affect transpirational cooling and carbon dioxide uptake for
photosynthesis.
c) what is autoclave? (verb and noun)
is a device to sterilize equipment and supplies by subjecting them to high pressure steam at 121° C or more.
d)If all plant cells are totipotent, what is the advantage of using a meristems?
It is virus-free!! =)
e)when we say "low in auxin" in plant cloning, this is relative to the auxin itself and not in comparison wtih cytokinins. Pls see diagram.
(a) other questions
http://chansensei.blogspot.com/2007/08/how-does-plant-virus-infect-plant.html
http://chansensei.blogspot.com/2007/07/complicated-matter-of-ti-plasmid.html
http://chansensei.blogspot.com/2007/07/callus-and-tumor.html
_____________ stem cell____________-
1) SCNT: read more:
(WIKI)
In SCNT the nucleus, which contains the organism's DNA, of a somatic cell (a body cell other than a sperm or egg cell) is removed and the rest of the cell discarded. At the same time, the nucleus of an egg cell is removed. The nucleus of the somatic cell is then inserted into the enucleated egg cell. After being inserted into the egg, the somatic cell nucleus is reprogrammed by the host cell. The egg, now containing the nucleus of a somatic cell, is stimulated with a shock and will begin to divide. After many mitotic divisions in culture, this single cell forms a blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to the original organism.
Some researchers use SCNT in stem cell research. The aim of carrying out this procedure is to obtain stem cells that are genetically matched to the donor organism. Presently, no human stem cell lines have been derived from SCNT research.
In 2005, a South Korean research team led by Professor Hwang Woo-suk, published claims to have derived stem cell lines via SCNT,[6] but supported those claims with fabricated data.[7] Recent evidence has proved that he in fact created a stem cell line from a parthenote.[8][9]
The impetus for SCNT-based stem cell research has been decreased by the development and improvement of alternative methods of generating stem cells. Methods to reprogram normal body cells into pluripotent stem cells were developed in humans in 2007. The following year, this method achieved a key goal of SCNT-based stem cell research: the derivation of pluripotent stem cell lines that have all genes linked to various diseases.[10] Some scientists working on SCNT-based stem cell research have recently moved to the new methods of induced pluripotent stem cells.
Stresses placed on both the egg cell and the introduced nucleus are enormous, leading to a high loss in resulting cells. For example, Dolly the sheep was born after 277 eggs were used for SCNT, which created 29 viable embryos. Only three of these embryos survived until birth, and only one survived to adulthood.[11] As the procedure currently cannot be automated, but has to be performed manually under a microscope, SCNT is very resource intensive. The biochemistry involved in reprogramming the differentiated somatic cell nucleus and activating the recipient egg is also far from understood.
In SCNT, not all of the donor cell's genetic information is transferred, as the donor cell's mitochondria that contain their own mitochondrial DNA are left behind. The resulting hybrid cells retain those mitochondrial structures which originally belonged to the egg. As a consequence, clones such as Dolly that are born from SCNT are not perfect copies of the donor of the nucleus.
Concerns
One concern is that blastula creation in SCNT-based human stem cell research will lead to the reproductive cloning of humans. Both processes use the same first step: the creation of a nuclear transferred embryo, most likely via SCNT. Those who hold this concern often advocate for strong regulation of SCNT to preclude implantation of any derived products for the intention of human reproduction. [17], or its prohibition.[14]
A second important concern is the appropriate source of the eggs that are needed. SCNT requires human eggs, which can only be obtained from women. The most common source of these eggs today are eggs that are produced and in excess of the clinical need during IVF treatment. This is a minimally invasive procedure, but it does carry some health risks, such as ovarian hyperstimulation syndrome, and in very rare instances even death
2) where can you find adult stem cells?
(definition given in test is okay -
ESC is based on origin: inner cell mass of blastocyst
ASC: undifferentiated cells found among differentiated cells in a tissue or organ
found in the body after embryonic devt, in growing
(http://stemcells.nih.gov/info/basics/basics4.asp)
(WIKI)
When to use the term ASC?
The term adult stem cell refers to any cell which is found in a developed organism
Also note:
Fetal stem cells are primitive cell types found in the organs of fetuses. The classification of fetal stem cells remains unclear and this type of stem cell is currently often grouped into an adult stem cell. However, a more clear distinction between the two cell types appears necessary.
___________others_________
Why is AP always generated at the muscles ?
Kindly ignore my reference on RMP in muscles with reference to the above.
AP is always generated because typically more than enuff ACh is released.
In fact the RMP os skeletal muscle fibre is about -70 to -90mV (similar to neurons) not -40mV. While that of smooth muscles (e.g. found in the heart) was the one that is around -55mV, very close to threshold potential!
Mmmm...that's all? :)
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