evolution
Summer Reading Suggestions from Scientists: Shirley Tilghman
Posted on by Dr. Shirley Tilghman
Non-Science Selection:
Viet Thanh Nguyen, The Sympathizer. In his brilliant debut novel, this American writer, who was born in Vietnam, uses the end and aftermath of the Vietnam War as a dramatic backdrop to explore the nature of identity and conflicts of loyalty, The anonymous narrator is a jumble of identities—the son of a Vietnamese woman and a French priest; a Communist working undercover as an aide to a South Vietnamese general; and a blood brother of both a C.I.A. assassin and a Vietcong leader. He believes in the revolution, but is haunted when he is required to murder in its name, and, ultimately, is abandoned by its leaders.
The narrative begins with a vivid portrayal of the last days of the fall of Saigon, as the narrator works feverishly to extract himself, his general and family off the rooftop of the American embassy. They ultimately land in California, where the general immediately begins to plot his return to Saigon. The narrator is hired to advise a filmmaker (referred to only as “the auteur,” but clearly meant to be Francis Ford Coppola) on a film about the war. The narrator believes he has been hired to give an authentic voice to the Vietnamese, whose sufferings and struggle have largely been untold in the West, but he fails in tragicomic fashion. In the end, the narrator is torn in two by his competing loyalties to politics and friendship. This is a deeply moving story of a young man in search of meaning in his life.
Science Selection:
Jonathan Weiner,The Beak of the Finch. The Pulitzer Prize winner for non-fiction in 1995, this masterful book tells the 25-year story of Peter and Rosemary Grant’s study of evolution in real time in the Galapagos Islands. Beginning in 1973, the Grants, who recently retired from the faculty of Princeton University, camped several months every year on a barren rock (Daphne Major) in the Galapagos, meticulously documenting the changes in size and shape of the beaks of Darwin’s famous finches in response to changes in climate. Thanks to the dramatic 1982-83 El Nino, the Grants were able to show that as the normally arid climate, which selected for finches with sturdy short beaks that are good at cracking dry hard seeds, became tropical, finches with long narrow beaks that could drink nectar from the now-abundant vegetation came to predominate. Natural selection in action! In the course of telling this extraordinary story of scientific inquiry, Weiner writes clearly and engagingly about how Charles Darwin and Alfred Russel Wallace developed the theory of natural selection, and why it is the cornerstone on which all of biology rests.
Shirley Tilghman
Credit: Denise Applewhite
Shirley M. Tilghman, PhD is president emerita and professor of molecular biology at Princeton University. She is well known for her scientific achievements as a mammalian developmental geneticist and for her national leadership on behalf of women in science. Her many accolades include: a Lifetime Achievement Award from the Society for Developmental Biology, the Genetics Society of America Medal, and the L’Oreal-UNESCO Award for Women in Science.
Gene Duplication: New Analysis Shows How Extra Copies Split the Work
Posted on by Dr. Francis Collins
The human genome contains more than 20,000 protein-coding genes, which carry the instructions for proteins essential to the structure and function of our cells, tissues and organs. Some of these genes are very similar to each other because, as the genomes of humans and other mammals evolve, glitches in DNA replication sometimes result in extra copies of a gene being made. Those duplicates can be passed along to subsequent generations and, on very rare occasions, usually at a much later point in time, acquire additional modifications that may enable them to serve new biological functions. By starting with a protein shape that has already been fine-tuned for one function, evolution can produce a new function more rapidly than starting from scratch.
Pretty cool! But it leads to a question that’s long perplexed evolutionary biologists: Why don’t duplicate genes vanish from the gene pool almost as soon as they appear? After all, instantly doubling the amount of protein produced in an organism is usually a recipe for disaster—just think what might happen to a human baby born with twice as much insulin or clotting factor as normal. At the very least, duplicate genes should be unnecessary and therefore vulnerable to being degraded into functionless pseudogenes as new mutations arise over time
An NIH-supported team offers a possible answer to this question in a study published in the journal Science. Based on their analysis of duplicate gene pairs in the human and mouse genomes, the researchers suggest that extra genes persist in the genome because of rapid changes in gene activity. Instead of the original gene producing 100 percent of a protein in the body, the gene duo quickly divvies up the job [1]. For instance, the original gene might produce roughly 50 percent and its duplicate the other 50 percent. Most importantly, organisms find the right balance and the duplicate genes can easily survive to be passed along to their offspring, providing fodder for continued evolution.
What Makes Our Brain Human? The Search for Answers
Posted on by Dr. Francis Collins
“The Thinker” by Auguste Rodin (photo by Brian Hillegas)
Humans’ most unique traits, such as speaking and abstract thinking, are rooted in the outer layer of our brains called the cerebral cortex. This convoluted sheet of grey matter is found in all mammals, but it is much larger and far more complex in Homo sapiens than in any other species. The cortex comprises nearly 80 percent of our brain mass, with some 16 billion neurons packed into more than 50 distinct, meticulously organized regions.
In an effort to explore the evolution of the human cortex, many researchers have looked to changes in the portion of the genome that codes for proteins. But a new paper, published in the journal Science [1], shows that protein-coding DNA provides only part of the answer. The new findings reveal that an even more critical component may be changes in the DNA sequences that regulate the activity of these genes.
DNA’s Double Anniversary
Posted on by Dr. Francis Collins
April 25 is a very special day. In 2003, Congress declared April 25th DNA Day to mark the date that James Watson and Francis Crick published their seminal one-page paper in Nature [1] describing the helical structure of DNA. That was 60 years ago. In that single page, they revealed how organisms elegantly store biological information and pass it from generation to generation; they discovered the molecular basis of evolution; and they effectively launched the era of modern biology.
But that’s not all that’s special about this date. It was ten years ago this month that we celebrated the completion of all of the original goals of the Human Genome Project (HGP), which produced a reference sequence of the 3 billion DNA letters that make up the instruction book for building and maintaining a human being. The $3 billion, 13-year project involved more than 2,000 scientists from six countries. As the scientist tasked with leading that effort, I remain immensely proud of the team. They worked tirelessly and creatively to do something once thought impossible, never worrying about who got the credit, and giving all of the data away immediately so that anyone who had a good idea about how to use it for human benefit could proceed immediately. Biology will never be the same. Medical research will never be the same.
DNA and the Roots of Hair Roots
Posted on by Dr. Francis Collins
Source: National Cancer Institute, NIH; Bill Branson, photographer.
It’s intriguing to find the roots of physical traits: skin color, height, and those weird tufts of hair on Uncle Mike’s ears. We’re all curious to know why we look the way we do. But new technologies are allowing us to discover the precise genetic roots of human traits that vary across the world. Variations in our DNA have helped us resist diseases and adapt to different climates and foods, enabling us to colonize just about every environment on the planet.
Recent studies have pinpointed variations responsible for lighter skin in Northern climates (such as SLC24A5 [1]) and the ability to tolerate milk sugar (lactose) in adulthood [2]. But a new NIH-funded study of a gene variant that arose in China adds a fascinating wrinkle—the use of a mouse model to help understand a potential human advantage [3]. (Regular readers will note that last week in this space I wrote about how mouse models could sometimes be misleading—this week the mouse is a champion!)
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