EAMCET Zoology

The 2009 Nobel Prize in Physiology or Medicine will go to three American geneticists—Elizabeth Blackburn, Carol Greider, and Jack Szostak. They who discovered telomeres, the genetic code that protects the ends of chromosomes, and telomerase, the enzyme that assists in this process, findings that are important in the study of cancer, aging and stem cells.

The work for which they received the award illuminated key aspects of the DNA replication process. As genetic material is copied from the chromosome during cell division, the whole DNA strand must be duplicated from end to end; otherwise, portions of genetic information will be lost. Until the 1980s, it was a mystery as to how the chromosomes could be reliably copied the whole way through without missing bits and pieces at the very end of each strand. Work completed by this year’s laureates demonstrated how, if parts of the end-cap telomeres were missing, DNA would eventually be shortened and cut off in the replication process.

Blackburn and Szostak in 1982 demonstrated that the telomere sequence could be isolated, inserted into another organism and still serve the same function. Working with Blackburn, Greider helped in 1989 to identify the RNA-based telomerase—the enzyme that creates the crucial telomeres. The findings have since been applied in studies of aging, stem cells and cancer.

Many mammals, including pigs, dogs, rabbits and cats have two uteruses. In these animals, multiple foetuses can grow in each uterus. The foetuses share the placenta, but each one has its own umbilical cord. All primates have single uteruses.

One in about every 2,000 women worldwide has a double uterus. About one in 25,000 women with uterus didelphys gets pregnant with twins, one to each uterus. (Hence the likelihood of any given woman growing two babies in two separate wombs is about one in 50 million).

In the embryonic stage of human development, a female has more than one "uterine horn," or tubes that ultimately fuse into one uterus. In people with this condition, somewhere in the developmental process the tubes didn't come together, most likely because there was an error in the signals cells received instructing them to migrate to certain places.

Some people with uterus didelphys also have two cervices (cervix is the narrow outer end of the uterus at its junction with vagina) and two vaginas, but some only have one vagina. (Most women with two vaginas do not get surgery to fuse them, because one side is typically bigger than the other, so they have intercourse using just that one side)

Most women aren't even aware they have the condition until they become pregnant and get an ultrasound exam. If she gets an ultrasound about eight weeks into her pregnancy (as most ob–gyns recommend), chances are the ultrasound technician would spot the extra womb. But if the woman doesn't get an ultrasound until 20 weeks or more into her pregnancy, the uterus housing the foetus might have grown big enough to overshadow the extra uterus in which case the ultrasound technician might not see it.

An obstetrician is a physician who has successfully completed specialized education and training in the management of pregnancy, labour, and pueperium (the time-period directly following childbirth).

A gynecologist is a physician who has a successfully completed specialized education and training in the health of the female reproductive system, including the diagnosis and treatment of disorders and diseases.

Typically, the education and training for both fields occurs concurrently. Thus, an obstetrician/gynecologist (OB/GYN) is a physician specialist who provides medical and surgical care to women and has particular expertise in pregnancy, childbirth, and disorders of the reproductive system. This includes preventative care, prenatal care, Pap test (a test for cancer of the cervix), detection of sexually transmitted diseases, screening, and family planning.

Bioluminescence is light produced by a chemical reaction within an organism. The protein which produces the light is generically called luciferin and the enzyme that catalyzes the reaction is called luciferase. The luciferase catalyzes the oxidation of luciferin resulting in light and an inactive oxyluciferin. In most cases, fresh luciferin must be brought into the system, either through the diet or by internal synthesis.

Sometimes the luciferin and luciferase as well as a co-factor such as oxygen, are bound together to form a single unit called a photoprotein. This molecule can be triggered to produce light when a particular type of ion (frequently Calcium)is added to the system .

Bioluminescence is not the same as "fluorescence" or "phosphorescence". In bioluminescence or chemiluminescence the excitation energy is supplied by a chemical reaction rather than from a source of light.

In fluorescence, energy from a source of light is absorbed and reemitted as another photon. Fluorescence does not occur in complete darkness.

1. An electron (yellow) "orbits" the nucleus (blue), minding its own business.
2. A source of light of an appropriate wavelength (indicating its energy) strikes.
3. It drives the electron into a higher-energy orbital.
4. The electron is only stable there for a short time.
5. Shortly it returns to the lower energy level.
6. This way it emits the energy as a longer wavelength photon.
7. The electron continues on its way.

Due to energy loss while in the excited state, the photon emitted will always be of longer wavelength (more red, lower energy) than the exciting photon. This is how laundry detergents can get things "whiter than white": by absorbing non-visible UV light and fluorescing in the visible spectrum.

Phosphorescence is similar to fluorescence except that the excited product is more stable, so that the time until the energy is released is much longer, resulting in a glow after the light has been removed. This is the basis behind glow-in-the-dark stickers.

Chemiluminescence is a general term for production of light when the excitation energy has come from a chemical reaction (as opposed to the absorption of photons, in fluorescence).

Bioluminescence is a subset of chemiluminescence, where the light-producing chemical reaction occurs inside an organism.

There are few basic luciferins (light emitters).