The Genetic Systems of Mitochondria and Plastids

It is widely accepted that mitochondria and plastids evolved from bacteria that were engulfed by nucleated ancestral cells. As a relic of this evolutionary past, both types of organelles contain their own genomes, as well as their own biosynthetic machinery for making RNA and organelle proteins. Mitochondria and plastids are never made from scratch, but instead arise by the growth and division of an existing mitochondrion or plastid. On average, each organelle must double in mass in each cell generation and then be distributed into each daughter cell. Even nondividing cells must replenish organelles...


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Science Journal Ranks Top 25 Unanswered Science Questions

By John Roach for National Geographic News

What is the universe made of? What is the biological basis of consciousness? How long can the human life span be extended?

These are just some of the as-yet-unanswered scientific questions pondered in the July 1 special 125th-anniversary issue of the academic journal Science.

Editor-in-chief Donald Kennedy and news editor Colin Norman tasked their staff to list the most challenging questions in science today...


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AIDS boss warns of PNG epidemic

Sunday, July 3, 2005; Posted: 3:17 a.m. EDT (07:17 GMT)

Asia has the second-largest number of people living with HIV/AIDS in the world after sub-Saharan Africa.

KOBE, Japan (AP) -- Papua New Guinea is at risk of an African-level HIV/AIDS epidemic, but other Asia-Pacific nations like Malaysia, Vietnam and Myanmar are also worrisome as the number of infections there continue to rise, the head of the U.N. AIDS agency has said.
The epidemic is as vast and diverse as the region itself with sex and injecting drug use the main engines driving the epidemic.

But there's simply not enough data to create a clear picture of the situation in many areas where other factors -- such as men who have sex with men -- could be contributing to rising numbers in cities and local communities, Dr. Peter Piot, head of UNAIDS


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Electrons in Atoms

Atomic Spectra Information

Atomic spectra are useful for identifying different elements. Each element has its own unique atomic spectrum. This section will show how a line spectrum is created and compare it to a continuous spectrum.

A continuous spectrum is one in which the colors blend from one to another. A good example of this is a rainbow, the reds blend into the oranges, which blend into the yellows, then to greens, blues, and violets. There is not a distinct division between the colors in a continuous spectrum. When looking through a diffraction grating at ...


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