Google+

Close look at DNA reveals basic processes of sex cell

Some scientists really throw themselves into their research, but Stanford University biophysicist Stephen Quake has taken the all-in approach to a whole new level.

Using his sperm, Quake and colleagues compiled the first-ever genetic blueprint for a single sperm cell. The results shed new light on molecular processes such as mutation and recombination in humans, Quake and his colleagues report in the July 20 Cell.

Figuring out how often humans make mistakes in copying DNA so that single DNA units are changed, or mutated, is important for a variety of reasons, including figuring out how long ago humans diverged from other species, says Laure Ségurel, an evolutionary geneticist at the University of Chicago. “Every calculation is based on this mutation rate,” she says.

In past studies, scientists estimated this rate either by comparing human DNA with that of other species to see how many changes have occurred since that species split from humans, or by studying families to see where children have different DNA than their parents. By studying individual sperm cells, Quake and colleagues calculate the human mutation rate at 2 to 4 changes per 100 million DNA units per generation. That is higher than the rate calculated by looking at families (SN Online: 6/13/11), but consistent with evolutionary estimates.

The new work also offers insights into how humans scramble their DNA so that children inherit different combinations of parental DNA. This process, called recombination, is thought to be directed by a protein called PRDM9, which latches on to DNA and governs where the breaks that allow gene swapping will happen (SN: 8/13/11, p. 17).

But the Stanford researchers found that PRDM9 isn’t always necessary for recombination. Many of the new recombination hot spots fall within transposons — mobile pieces of DNA often called “jumping genes” — that don’t have obvious places for PRDM9 to grab.

Just because PRDM9 doesn’t seem to grasp DNA directly everywhere recombination happens doesn’t mean the protein isn’t involved in every gene swap, says Ségurel.

Regardless of PRDM9’s involvement, the data suggest that transposons may have had an important hand in shaping human evolution, Quake says. “This is a nice mark in the transposon column.”

The work also represents a technical accomplishment: Researchers have begun deciphering the genetic makeup of single cells, such as cancer cells, but this is the first time anyone has compiled a genetic blueprint from a single sperm.

Sperm are challenging for genetic analysis because they contain so little DNA, says Stanford biological engineer Jianbin Wang, a study coauthor. Sperm and eggs each contain half as much genetic material as a typical body cell.

On the flip side, sperm have given scientists an advantage when analyzing the small portion of the genome that contains protein-coding genes, Quake says. With only one copy of each gene per sperm, researchers don’t mix up two copies with each other.

“For 99 percent of the genome it is more challenging,” Quake says of single sperm analysis, “but for 1 percent it’s easier. That’s a pretty important 1 percent.”

Source:  Science News / Tina Hesman Saey /

Entertainment

Raunchy Adaptation of Classic TV Series Arrives on Home Video

  Chips DVD Review by Kam Williams Raunchy Adaptation of Classic TV Series Arrives on Home Video Whenever a classic television series is made into a movie, the buzz always seems to be about whether the screen version will be a creative variation on the theme or merely a campy, cornball, take-the-money-and-run ripoff trading in familiar formulas and shopworn cliches. After all, for every inspired adaptation like Batman (1989), Charlie's … [Read More its Good for You.....]

Books

Gil’s Goodwill!

  Gil Robertson The “Book of Black Heroes” Interview with Kam Williams Gil's Goodwill! For nearly three decades, writer/author Gil L. Robertson, IV has used the written word to enlighten, empower and uplift. The one-time political organizer initially made his mark in entertainment journalism, penning over 50 national magazine covers and contributing bylines to a wide range of publications that include the Los Angeles Times, the Atlanta … [Read More its Good for You...]

Art

The Day After the Day Of

  The Day After the Day Of by Paul Ilechko   The sky sheds its tears. This morning is the morning of the day after. The day of mourning, the day after the day of.  I beseech the sky to shed tears in order to wash away the tears on my face.   This is the first day of the time after. This is the beginning of a new time, the days of pain, the days of sorrow. We are in mourning. The sky looks down and sheds its tears for … [Read More its Good For You...]

Real Estate

How to Hire a Winner in Real Estate

  How to Hire a Winner in Real Estate by Amy Lignor   You want to buy that new house because the twins are on their way. Little Betty and Little John are already there, but who knew you would have even more so soon? What’s that? Oh…well, of course, in order to buy that new home with four bedrooms instead of two, you will also need to sell your present homestead in order to get the money needed to start paying on a new one. And, of … [Read More its Good for You.....]

Lifestyle

Ejogo’s Largo!

    Carmen Ejogo The “It Comes at Night” Interview with Kam Williams Ejogo's Largo! Carmen Ejogo has established a distinguished career in both feature films and television. She is best known thus far for her leading role of civil rights activist ‘Coretta Scott King’ opposite David Oyelowo in Ava DuVernay's universally acclaimed SELMA as well as being singled out for her ‘mind-blowing’ lead role as Sister in SPARKLE alongside … [Read More its Good for You...]

Outdoors

Tidewater 230 LXF Combines Luxury, Family Friendly Features

  Tidewater 230 LXF Combines Luxury, Family Friendly Features By Craig Lamb Are you looking for a family friendly, center console fishing rig in the 23-foot class? Your search is over with the 230 LXF from Tidewater Boats. The all-new 230 LXF has a centerline of 23’ with a wide beam spanning 8’ 10.” The boat weighs 3,200 pounds and has a fuel capacity of 95 gallons for peace of mind on long trips. Best balance of performance and fuel … [Read More its Good for You...]

Sports

You Don’t Have to be Greek to be a “Zorba” Fanatic

  You Don’t Have to be Greek to be a “Zorba” Fanatic by Amy Lignor   No, the sport is not called ‘Zorba’, but it most definitely fits for this article’s title. This most unusual sport is actually called ‘Zorbing’, and has caught on like wildfire across the globe. And now, seeing as that the NBA has wrapped, with Golden State proving that they were determined to make amends for last season; and with the NHL closing up shop for the season … [Read More its Good for You...]

Business

Add Value with Summer Home Renovation Projects

  Add Value with Summer Home Renovation Projects by Amy Lignor   There are a whole list of summer activities for you and the kids planned. Most of them, of course, you want to be nothing but fun, such as grilling outside on the patio or swimming in the pool. However, having the backyard pool and patio are two things you really need in place before either of those activities could be enjoyed. And building this area could be a great … [Read More its Good for You...]

Travel

Finding Relaxation in the Most Remote Locations of All

    Finding Relaxation in the Most Remote Locations of All by Amy Lignor   It is a fact that the largest travel locations are also beyond popular. Among the downsides of this fact is that when you’re looking for peace, quiet, and basically a chance to do nothing more than spend time with yourself and, perhaps, one other best friend, the most popular places don’t offer that. In other words, it is the most remote (sometimes most … [Read More its Good for You...]

Green Living

Creating the Perfect Vegetable Garden

  Creating the Perfect Vegetable Garden by Amy Lignor   Many are still dealing with that wintery mix Mother Nature just loves to toss down from the sky this time of year. Yet, that gardener living inside the soul – the one just dreaming of the sunny skies and lazy rainy days that are must-haves in order to grow the best vegetables possible – is already jotting down the facts, tricks and tips they need to know in order to make that … [Read More its Good for You...]