Tracing Traits: Genetics (The Science of Life) by Christine Petersen

Have you ever heard that you look like family members? Children inherit features such as hair, eye, and skin color from their parents. These traits are passed along in genes... special codes contained in the cells of your body. They determine all of your inherited traits. Genetics is a part of biology that studies how traits are passed from one generation to the next.

Because genetics is the blockbuster branch of twenty-first century biology, students need to understand the basics of this rapidly-moving field. Christine Petersen's Genetics (The Science of Life) (Abdo Publishing, 2014) shows how geneticists are learning how our DNA affects our looks, health, intelligence, and life span, and how the secrets in human, animal, and plant genes reveal how life evolved on earth, how we can repair genetic health problems, and even offer new clues to sleuth out criminals.

Petersen opens with a summary of the history of what she calls "The Secret in the Cells," the story of how earlier biologists, from the first "microscopist," Robert Hooke, who first saw and named "cells" and pioneer tracer of traits Gregor Mendel, through Swiss biologist Carl Nageli, who in 1842 was the first to observe in the cell long strands of some unknown material, the chromosomes, to American Thomas Morgan, who observed how genes within the fruit fly chromosomes determine eye color and led biologists to the next step, the untangling of DNA.

Petersen gives a chapter to the "DNA Code," the unraveling of those long molecules, the chromosomes and the deoxyribonucleic acid from which they are made. She tells the story how Rosalind Franklin and Maurice Wilkins actually photographed DNA, revealing its "ghostly X shape" that led James Watson and Francis Crick to conceive the now famous double helix form of DNA and its decoding in the Human Genome Project, completed in 2003.

Cells control all the functions needed for life. Although each cell contains the same DNA, there are more than 200 different cell types. This is possible because genes withing a particular cell can be turned off or on. The genetic code tells individual cells what o become and how to function. Cells work together to build muscle, skin, bone, and other parts of the body.

Genes are sections of DNA containing thousands of base pairs that work together. Each gene provides instructions for making a protein. Several genes often work together to produce a single trait.

Petersen's final expository chapter takes the reader through the processes of mitosis (cell division) and meiosis (reproduction) which make life possible, discussing mutations that occur during these processes, and the effects of environment upon these processes throughout biological history. Her final chapter looks forward to the uses that this hard-earned knowledge may be put, the science of using human stem cells to repair or even grown new tissue and organs to cure disease. She touches briefly on genetic engineering in agriculture, and even describes speculation about re-engineering recently extinct species such as the passenger pigeon, the ivory-billed woodpecker, as well as the long-gone woolly mammoth, from whose frozen bodies complete DNA has been recovered.

These possibilities in genetics provide intriguing possibilities for young people considering careers in this rapidly advancing field, but basic knowledge of this discipline is important for all future adults whose jobs may never involve a microscope. Future uses of genetics will involve all of society, requiring everyone to understand what the stakes are in these possibilities. Petersen's Genetics (The Science of Life) is an easy-to-understand summary of the field of genetics, amply illustrated which raises ideas of the amazing potential and problems that it engenders, ably written for readers of middle school science.

A brief glossary, bibliograpy, and index are appended, and the editors offer Common Core-coordinated topics to expand understanding, such as debating whether bringing back extinct species--the passenger pigeon, the ivory-billed woodpecker, the recently lost Tasmanian wolf, for example--should be re-engineered from the DNA in museum freezers.

How about bringing back the great auk, an arctic cousin of the antarctic penguins, or even Cro-Magnon man, for whom we have just recovered DNA? Beyond the "gee-whiz" allure of such possibilities, what place such new-old species would have in our modern world? Would the great auk find enough fish to survive in our depleted northern oceans? Would Cro-Magnons dominate the NFL? Complex as it is, genetics has its allure, and this book is a good beginning for young readers to begin thinking about those choices.