Wednesday, March 28, 2007

Pretty Fireflies

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Have you ever wondered how fireflies glow in the dark and why do they glow? They make use of bioluminescence!

Bioluminescence is the ability of living things to emit light. It is found in many marine animals, both invertebrates (e.g., some cnidarians, crustaceans, squid) and vertebrates (some fishes); some terrestrial animals (e.g., fireflies, some centipedes); some fungi and bacteria (photo at left).

Fireflies use their flashes to attract mates or prey. The pattern differs from species to species. In one species, the females sometimes mimic the pattern used by females of another species. When the males of the second species respond to these "femmes fatales", they are eaten!

The firefly is capable of producing a "cold light" containing no ultra violet rays, with a wavelength from 510 to 670 nanometers, pale yellowish or reddish green in color, with a lighting efficiency of 96%.

There are more than 2000 species of firefly, found in temperate and tropical environments around the world. Many species can be found in marshes or in wet, wooded areas where their larvae have more abundant sources of food.

The luminescence involves a luciferin (a light-emitting substrate), a luciferase (an enzyme that catalyzes the reaction), ATP (the source of energy) and molecular oxygen. Generally, the more ATP is available, the brighter the light.

How fireflies turn their luminescent organs — called lanterns — on:

1.The luminescent cells of the lanterns are close to cells at the end of the tracheoles (that bring oxygen to — and take carbon dioxide away from — the insect's tissues).
2. These cells contain nitric oxide synthase (NOS), the enzyme that liberates the gas nitric oxide (NO) from arginine.
3. Nerve impulses activate the release of NO from these cells.
4. The NO diffuses into the lantern cells and inhibits cellular respiration in the mitochondria (probably by blocking the action of cytochrome c oxidase)
5. With cellular respiration inhibited, the oxygen content of the cells increases.
6. This turns on light production in the peroxisomes that contain luciferase and luciferin-ATP (the ATP is generated when the lanterns are dark).
7. The quick decay of NO probably contributes to the short duration of the flash.

Wednesday, February 28, 2007

Armoured Sea Robin - Contributed by Leon Jin (1L)

Description—
The armored robin resembles the sea robins in general body form, and in the arrangement of its fins, including the fact that the two lower rays of each pectoral form separate feelers. But its body is entirely clothed with bony plates of considerable size. There are 4 rows of these on each side, from the vent rearward, with an equal number of rows of thornlike spines, the latter close set and directed rearward. The plates on the abdomen have no spines. Thanks to this armor, the trunk is very stiff. The lower jaw bears a number of short fleshy barbels; there is one long barbel with short side branches at each corner of the mouth; and the front of its head is given so peculiar an appearance by the two projections from the skull that the armored robin could hardly be mistaken for any other fish, except for one of its own tribe.

Color—
Bright crimson, below and above.

Size—
Maximum recorded length between 13 and 14 inches (330-355 mm.).

Habits —
This is a ground fish, recorded from depths ranging from 50 fathoms down to somewhere between 200 and 235 fathoms. And it seems to be confined to the zone of warm water along the outer part of the continental shelf and upper part of the continental slope for the lowest temperature in which it has been recorded is between 44° and 45°. The stomachs of those that have been opened contained shrimps, stomatopods, and other small crustaceans.

Saturday, February 24, 2007

Cloning II

Should Humans be Cloned?

Physicians from the American Medical Association and scientists with the American Association for the Advancement of Science have issued formal public statements advising against human reproductive cloning. Currently, the U.S. Congress is considering the passage of legislation that could ban human cloning.

Due to the inefficiency of animal cloning (only about 1 or 2 viable offspring for every 100 experiments) and the lack of understanding about reproductive cloning, many scientists and physicians strongly believe that it would be unethical to attempt to clone humans. Several cloned animals have died prematurely from infections and other complications. The same problems would be expected in human cloning. In addition, scientists do not know how cloning could impact mental development. While factors such as intellect and mood may not be as important for a cow or a mouse, they are crucial for the development of healthy humans. With so many unknowns concerning reproductive cloning, the attempt to clone humans at this time is considered potentially dangerous and ethically irresponsible.

With the many unethical issues, why are we still so concerned over cloning? It must have its advantages and uses!

Technology related to cloning can be used to improve taste and nutritional value or provide resistance to particular types of disease can be used to genetically engineer food crops. Animals can be genetically altered to serve as models for studying human diseases.

Reproductive cloning also could be used to repopulate endangered animals or animals that are difficult to breed.Cloning extinct animals presents a much greater challenge to scientists because the egg and the surrogate needed to create the cloned embryo would be of a species different from the clone.

Therapeutic cloning technology may some day be used in humans to produce whole organs from single cells or to produce healthy cells that can replace damaged cells in degenerative diseases such as Alzheimer's or Parkinson's. Much work still need to be done before therapeutic cloning can become a realistic option for the treatment of disorders.

DollyCelebrity Sheep Has Died at Age 6

Dolly, the first mammal to be cloned from adult DNA, was put down by lethal injection Feb. 14, 2003. Prior to her death, Dolly had been suffering from lung cancer and crippling arthritis. Although most Finn Dorset sheep live to be 11 to 12 years of age, postmortem examination of Dolly seemed to indicate that, other than her cancer and arthritis, she appeared to be quite normal. The unnamed sheep from which Dolly was cloned had died several years prior to her creation. Dolly was a mother to six lambs, bred the old-fashioned way.

Friday, February 23, 2007

Cloning

Have you ever wondered how another exact copy of living creature could be created? Most of us would have heard ‘Dolly’ the sheep before. Dolly looks just like her mum.

To clone a gene, we first require a DNA fragment containing the gene of interest to be isolated from chromosomal DNA using restriction enzymes and then write it with a plasmid that has been cut with the same restriction enzymes.

Many of you might think that ‘Dolly’ the sheep was the first animal to be cloned. Hehe.. But you are wrong. The first animal that was cloned was a tadpole. Before Dolly was created, the first mammal cloned from the cell of a grown-up animal, the clones were created from embryonic cells.

Since Dolly, scientists have cloned both large and small animals like the sheep, pigs, cats, rabbits, goats, cows and even gaur.

Do you think whatever you like to clone would be successful?
Cloning of monkeys, chickens, horses and dogs have not been successful.

Some species are more resistant to ell nuclear transfer than others. Improvements in cloning technologies are needed so that many species can be cloned successfully but of course this concerns ethical and moral issues too, especially in the case of human beings.

Process of Cloning Dolly

Picture showing the Process of Cloning Dolly

Thursday, February 22, 2007

Something for all the night owls. =)


Click on the image to enlarge it.

Wednesday, February 21, 2007

Roses are BLUE

Did you receive a blue rose for Valentines' or hoping for your prince charming to give you a big bouquet of blue roses?

Roses are red, that is what we all know. Roses also come naturally in colours such as white, yellow and pink. Now we have man-made roses which are champagne (yellow orange) and blue! Blue roses were dyed in the past. However recently, they can be grown naturally using genetic engineering!

Blue is a particularly difficult colour to achieve because of the complex genetic and environmental cues. The pigment that makes some other flowers (eg. carnation) blue is called delphinidin, but roses lack the genes to produce it.

5-petaled pansies The blue rose that was successfully created was made by introducing blue genes extracted from pansies (picture on left). Differing from previous efforts to produce blue roses through existing hybridization technology, the petals of the roses were altered so that they were composed almost entirely of delphinidin, making it possible to breed varieties more susceptible to hybridization. While the rose is referred to as "blue," its actual color is closer to blueish-purple. The RNAi technology is used to remove the gene encoding the enzyme dihydroflavonol reductase (DFR) in roses. Simply saying, the gene functions of the plant was manipulated.

*Delphinidin is a primary plant pigment. Delphinidin gives blue hues to flowers like violas and delphiniums. It also gives the blue-red color of the grape and can be found in cranberries.*

So we can all look forward to more blue roses in the florists soon!!

Wednesday, February 7, 2007

More About Yeast

Yeast belong to a group of organisms known as fungi. Some types of yeast include wet yeast, instant yeast and active dry yeast. Most yeasts are unicellular, although yeasts may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or true hyphae as seen in most moulds. They do not contain chlorophyll, hence unable to make their own food. They feed on sugar from a variety of sources. These sugars are then broken down into carbon dioxide and water. Only under anaerobic conditions, such as alcoholic fermentation, is yeast able to produce ethanol and carbon dioxide. (Are you able to write the word equation?)

Yeast, is used in baking as a leavening agent, where it converts the fermentable sugars present in the dough into carbon dioxide. This causes the dough to expand or rise as the carbon dioxide forms pockets or bubbles. When the dough is baked, it "sets" and the pockets remain, giving the baked product a soft and spongy texture. The primary function of yeast is to supply carbon dioxide gas which inflates the dough during proof and the early stages of baking.

The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts. Salt and fats such as butter slow down yeast growth.

Where else is yeast used? In Marmite! And also, beverages such as wine(sake = japanese rice wine), beer, or distilled spirits all use yeast at some stage of their production!

Tuesday, February 6, 2007

Queries on Twins

Hi Kenneth Neo, identical twins, formed when one fertilized egg splits, are the only people in the world with identical DNA. Fraternal twins, on the other hand, are formed when two different eggs are fertilized. Genetically speaking, fraternal twins are no closer than normal siblings, sharing only about 50% of their genes.

Although identical twins have the same genotype, or DNA, they have different phenotypes, meaning that the same DNA is expressed in different ways.

Traits determined by phenotype, such as fingerprints and physical appearance, are the result of "the interaction of the individual's genes and the developmental environment in the uterus. Thus, a DNA test can't determine the difference between identical twins, while a simple fingerprint can. You can read more on Twins here.

Valerie, you can find your answers here. Click on more links at the bottom of the page!

Saturday, February 3, 2007

Photosynthesis for you if you're still "lost"

Dear all, here's a video giving an excellent recap of the section on Photosynthesis in Unit 15. =) Enjoy.

Queries

Dear students, this blog is managed by a team of teachers namely, Ms Chan, Mr Jimmy Tan, Mdm Hidayah, Mr Wee, Ms Boh and myself Ms Ng. We are glad you all like the layout of this blog! Do remember to bookmark this page and check frequently!

If you have queries, I suggest you "find out" the answers on your own and post them under "Comments". We will look through your posts and give comments. (Note: DO NOT directly copy and paste from websites. Summarise and provide references, that is, where you took the information from.)

Leon Jin, you mentioned on "armoured sea robin". How about doing a short write-up on it to share with everybody? You can include pictures too! You can email to us (email address below) and we'll post it up for you.


Chelsea, regarding your question, the diameter of the DNA helix is about 2 nm and the vertical rise per base pair is 0.34 nm.

How small is 1 nm? (Note: nm is nanometer, similar to cm as centimeter)

1 nm = 0.000000001 m

So have you got an idea on the size?

- Ms Ng -

Thursday, February 1, 2007

Self-Cleaning Fabrics Cause A Flutter

Imagine playing rugby in the rain, and finishing the match to find your kit is both dry and sparklingly clean. This may sound far fetched, but could be possible in the future thanks to butterflies and researchers in China.

A team of researchers led by Lei Jiang at the Chinese Academy of Sciences, Beijing, have discovered how blue Morpho butterflies (Morpho aega) keep their wings clean and dry. Jiang hopes this finding can be applied to self-cleaning fabric coatings.

butterfly

These tropical butterflies from Central and South America have very fine scales on the surface of their wings. Jiang found that the wings can react differently to water depending on the direction the wing is pointing. As the butterfly tips its wing downwards in flight, droplets of water roll away from the body carrying dust and dirt with them. As the butterfly wing is tipped upwards the direction of the scales prevents the droplet from moving towards the butterfly’s body.

Jiang has discovered a new feature for self-cleaning surfaces, said Ivan Parkin of University College London, an expert in materials chemistry. However, Parkin is unsure how this surface could be manufactured on a large scale, adding that ‘harvesting butterflies would not be an ideal method!’

Nina Athey-Pollard

Ever Wonder How White Blood Cells Consume Plastic Beads?

White Blood Cells (WBC) are our army against germs, bacteria and viruses. Check out the latest research findings on it! Click here to find out more!