Al Stahler: A precious inheritance
The instructions for assembling our bodies – two eyes, one nose (more-or-less half-way between) – these instructions are written in our genes. We inherited these instructions from our parents, who inherited them from their parents. Genes are passed downward, one generation to the next: vertical transmission.
Bacteria with a gene for antibiotic resistance pass that gene on, vertically, to their offspring. But they can also pass the resistance gene from one microbe to another, no parents involved: horizontal – sideways – transmission.
Higher organisms can also acquire genes through horizontal transmission. Some of the genes we’ve acquired horizontally are vitally important to us. Others we could do without.
Horizontal gene transfer happens whenever we catch a virus. Having been transferred into us, those viral genes proceed to hijack our bodies, coerce our bodies to replicate – duplicate – the viral genes, which will then infect yet more parts of our body, and – ultimately – infect other bodies.
Fortunately, we can defend ourselves against horizontal gene transmission. Our immune system – systems, plural, really – fight off bacteria that see us as food … fight off viruses that see us as gene-replicating robots.
Our bodies’ instructions are written in our genes, written in an alphabet composed of microscopic jig-saw puzzle pieces – 3-dimensional jig-saw puzzle pieces, read, by feel, by microscopic reading machines inside our cells. Strung together, the jig-saw letters spell out words; words, in turn, are strung together to make genes – instruction manuals for assembling and running our bodies.
When we write for each other, we leave clues about ourselves. Coming upon the word for “funniness” spelled “humor” or “humour,” the reader can figure out on which side of the Atlantic the writer lives.
The same sorts of clues are written into our genes. Humans and chimpanzees share almost all the same genes – over 95%. Go back some five million years, and we find that humans and chimps share the same great-great-, many times-great, grandparents.
Go back another couple of millions of years, and we find that both chimpanzees and humans share great-greats – and genes – with gorillas.
But, over the years, the spellings of those genes have changed, which is how we know that we’re closer to chimps than we are to gorillas – our genes, and those of gorillas, have more differences in spelling.
Looking at the genes for assembling our immune systems, we find we share some of those genes with cousins going back half-a-billion years. We share our immune system genes with frogs and toads, lizards and fish. Where did those genes come from, half-a-billion years ago?
Surprisingly, some of those immune system genes look – for all the world – like viral genes … genes from a virus.
No one is saying that one of our great-great-many-times-great grandparents was a virus. Rather, it seems that – half-a-billion years ago – good parts of our immune systems were transferred to us – horizontally … sideways – by viruses.
Why … on Earth … would a virus want to give us an immune system?
Contract a viral infection and your energy level drops. When your body’s been hijacked, you’re putting much of your energy into making more viruses.
The last thing a virus wants is competition – another virus, taking up residence in your body, draining off energy. Half-a-billion years ago, viruses infecting early animals evolved ways to keep out the competition, they invented an immune system — multiple immune systems to keep other viruses out of their replication robots, out of us animals.
Warm air rises. Where the sun shines brightest – in the tropics – air warms most, and rises highest. As warm air rises, air lower down rushes in, from north and south, to replace it.
Looking down from space, we can see warm air rising, wherever it’s afternoon in the tropics. Moisture in the rising air condenses to form cumulus clouds, and thunderstorms rain down on the tropical rain forests below.
Warm air rises … until it reaches air as warm as it is. The air then stops rising, and moves sideways, to the north, to the south.
What goes up, must come down. As air moves away from the tropics, it cools, and begins to descend.
While rising air creates tropical rain forests, sinking air creates deserts. And it piles up, forming humongous mounds of air. One such mound is the North Pacific High Pressure System – the North Pacific High (North Pacific refers to any part of the Pacific north of the equator).
The North Pacific High is a barrier to the jet stream, and to the storms the jet stream steers across the Pacific.
When it’s wintertime in the northern hemisphere, the sun shines brightly on the southern hemisphere, and the line of rising warm air moves south. The North Pacific High follows it down, allowing wintertime storms to reach California.
Come summer, the sun and tropical rainstorms and the North Pacific High migrate northward. Few storms make it into California in summer.
The North Pacific High, of course, is made of air … it can swell, shrink, move about — especially in spring — allowing welcome springtime rain to reach us.
The air above us evolves – the air grows moist, then dries, winds blow this way, then that. Such changes are hard to track by eye alone. But the clouds respond to the air, and the clouds evolve – day-to-day, hour-to-hour, moment-to-moment.
Al Stahler enjoys sharing science and nature with friends and neighbors on KVMR-FM, and can be reached at email@example.com.
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