Tag Archives: DNA

How These All-Female Lizards Are Able to Reproduce and Thrive Without the Help of Any Males

As far back as the 1960s, scientists were aware that a number of whiptail lizards in Mexico and the southwestern United States were made up entirely of females.

The most notable of these species, the New Mexico whiptail lizard, is able to reproduce healthy, well-bred offspring without the aid of male fertilization.

Whiptails aren’t the only species that reproduce asexually. In fact, there are 70 other vertebrate species that can do it. But the New Mexico whiptail may have unlocked the secret as to how it’s possible for a species that produces exclusively asexually to thrive.

Komodo dragons are among the vertebrate species that are able to reproduce asexually

Peter Baumann works at the Stowers Institute for Medical Research in Kansas City, Missouri. He co-authored a study on the lizards that was published in the journal Nature back in 2010.

Baumann explains that parthenogenteic species (species that reproduce without fertilization), are genetically isolated because they only inherit the DNA of one parent.

This means that any genetic weaknesses, like susceptibility to a disease or physical mutation, can’t be “overridden” by healthy genes from a second parent. The shallower the gene pool, the more likely it is to produce sick or mutated offspring.

To deal with this issue, the all-female whiptail lizard species have evolved to start the reproductive process with twice as many chromosomes as their sexually-producing lizard relatives.

New Mexico whiptail lizards were actually the result of two different species of lizard (the western whiptail and little striped whiptail) interbreeding to form a hybrid species. Because of this, these all-female lizards are equipped with a very diverse gene pool.

Left: little striped whiptail. Middle: New Mexico whiptail. Right: tiger whiptail. Click to enlarge

Instead of combining homologous chromosomes (like sexual species do, getting one set from each parent), the lizards pair recombined sister chromosomes instead. This maintains heterozygosity in the offspring.

Here’s a more simple way to think about it. Every one one us has DNA from generations and generations of our ancestors. When we reproduce, we combine our DNA with our partner’s- the resulting offspring’s genetic codes contains parts of both parents’ DNA.

But since we have such vast genetic diversity from all of our ancestors, the exact coding of the genes we pass along when we reproduce isn’t always the same, which is why brothers and sisters don’t all look the same.

A basic way to visualize how genetic information is passed on in sexual reproduction. Note that the “marbles” passed on by each individual parent are different for the two children. Click to enlarge

So, rather than combining its genetic code with that of a male, the whiptail lizard combines two different versions of its own DNA code, ensuring that each pairing of sister chromosomes will have multiple alleles (different forms of a gene), which gives the offspring the genetic diversity it needs to be healthy.

This discovery means that,

“these lizards have a way of distinguishing sister from homologous chromosomes,”

says Baumann. How do they do this? The researchers aren’t sure yet, but it’s the next question they will be investigating, along with the question of how they evolved to start reproduction with double the normal amount of chromosomes.

Female whiptail lizards perform courtship rituals with one another to stimulate ovulation. The top lizard will lay smaller eggs while the one on the bottom will lay larger eggs. They switch spots every mating season. Click to enlarge

Though it may seem like asexual reproduction would eventually hurt a species in the long run, Baumann also pointed that,

“You’re greatly increasing the chances of populating a new habitat if it only takes one individual.”

It seems to be working pretty well for these lizard ladies.

Read the original story from the Scientific American here.

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Australia’s Famous Albino Humpback Whale Makes A Rare Appearance (Video)

More than 160 years ago, in 1851, Herman Melville published one of the most famous books in American literature history. Moby Dick tells the story of a massive white whale and a ship captain (Ahab) bent on getting revenge for a leg he lost trying to battle the beast.

The story of Australia’s famous albino humbpack whale is quite different. Migaloo (which means “white fella” in one of Australia’s aboriginal languages), was first discovered back in 1991. It’s estimated he was between 3-5 years old at that time.

Migaloo the albino humpback (Image Courtesy of Jenny Dean)

Every winter, more than 12,000 humpbacks migrate up Australia’s east coast to reach warmer waters. While most humpbacks stay in deep waters well of the coast, some of them, like Migaloo, prefer to travel closer to shore, where humans can see them.

Every year, countless people flock to Australian waters hoping to catch a glimpse. Although he is not the only white humpback in the world, Migaloo’s tendency to swim in waters close to shore has made him probably the most famous. He has his own twitter account and you can even buy his songs on iTunes.

This past January, Migaloo made a rare appearance with a few of his buddies, putting on quite the show for anyone lucky enough to catch it. You can watch some of the footage below.

Why is he white? Questions were initially raised as to whether Migaloo was actually albino after it was discovered that his eyes were actually brown (most albinos have red or white eyes).

However, a study of Migaloo’s DNA revealed that he had a genetic mutation which truncated the protein that produces melanin, the substance which gives our skin its color. This finding proved Migaloo was a true albino.

(h/t IFL Science)

How Unemployment Is Literally Shortening Men’s Lives

A team of researchers from the Imperial College of London and the University of Oulu in Finland recently conducted a study where they examined the DNA of 5,620 men and women born in Finland in 1966.

The researchers were measuring the subjects’ telomeres. Telomeres are the structures at the ends of our chromosomes which protect our genetic code. They naturally wear away and shorten as we age, so scientists are able to use them as a biological marker for aging.

Telomeres and DNA structure

The researchers examined DNA samples from 1997 when the subjects were all 31. What they found was that men who had been unemployed for more than 2 of the 3 years before the samples were taken were more than twice as likely to have shorter telomeres compared to men who were employed continuously.

The study also accounted for a number of other, “social, biological and behavioural factors” to rule out the possibility that the short telomeres were a result of other causes.

This trend was not observed in the women in the study, however.

Read the full story here.

A Comet Collision on Jupiter’s Moon Europa May Have Delivered the Building Blocks for Life

NASA’s Galileo mission to Jupiter has revealed evidence of a “Spectacular Collision on the Surface of Europa”. Europa is one of over 60 moons that orbit Jupiter. This moon has attracted a lot of attention since New Evidence for Liquid Water on Europa has been discovered.

NASA spacecraft has revealed evidence a colossal impact on Jupiter’s moon Europa, a collision that may have delivered key minerals and perhaps even the raw ingredients for life, scientists say.”

According to Space.com

Many believe Europa may be one of the best places to look for extraterrestrial life in our solar system. Beneath its icy outer crust (up to sixty miles deep), the moon is thought to be hiding a saltwater ocean. Scientists have also suspected that Europa is home to many organic materials, the type of carbon-based materials that make up the building blocks of life like DNA and proteins.

Jim Shirley a research scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California said in a statement (Dec. 11)

Organic materials, which are important building blocks for life, are often found in comets and primitive asteroids. Finding the rocky residues of this comet crash on Europa’s surface may open up a new chapter in the story of the search for life on Europa.”

Shirley and colleagues made the discovery while looking at 15-year-old near-infrared images from NASA’s Galileo Spacecraft, which arrived at Jupiter in 1995 and circled the gas giant for about eight years. If this comet hit during the eight year span of time we were watching, I wonder if another comet may have hit before?

Check Out the below Pictures of Europa