‘Inheritance’ a crash-course in genetics

By A Contributor

Our biology teachers lied to us. The Mendelian Laws of Inheritance are not eternal, immutable truths. Indeed, strictly speaking, they are not true at all.

Sharon Moalem, a medical doctor, geneticist, and New York Times best-selling author, has made a study of genetic abnormalities, their sources, and effects. In “Inheritance,” he presents the modern view that genes in all life forms are constantly changing, either spontaneously, or in response to internal and external stimuli.

Gregor Mendel, an Austrian Augustinian friar, is best known to us for his work on the inheritance patterns of seven genetic characteristics in peas.

He published his “Experiments in Plant Hybridization” (1865) in which he posited his “Law of Segregation” and “Law of Independent Assortment.” These laws stated that genes were either dominant or recessive, and they were unchanging in their characteristics.

Charles Darwin’s “The Origin of Species” (1859) said that while genes mutated, they were inexplicable, rare occurrences. Whereas Darwin immediately gained a prominence which he has retained to this day, Mendel’s work was regarded as studies in hybridization, not genetics, and was forgotten until the early twentieth century.

Moalem tells us of Mendel’s discoveries, but then tells us that today’s theory of epigenetics holds that genetic traits can change and be passed to the next generation.

In other words, the three billion nucleotides (adenosine, thymine, cytosine, and guanine, or ATCG) that make up human genes (DNA) can change in their formation and expressions, and mutations occur all of the time in response to the events, stresses, or demands placed on them by occurrences in an individual’s life.

He takes seemingly unrelated events and genetic characteristics, especially defects, and shows how they relate to each other.

The third chapter is an example of this.

In it, we e see how changes in genetic expression in bees, mice, and humans come from diet, methylation, stress, bullying, tragic events, and other things.

In the course of doing this, he tells us the perhaps incomprehensible technical name of a syndrome or gene and thereafter refers to it by its acronym; for example, argininosuccinic aciduria becomes ASA, which is much easier to remember. He also tells us what a certain specific gene or group of genes affects.

For example, Type 1 Waardenburg Syndrome, which affects hair and eye coloring, is caused by changes in a gene called PAX3. Mutant eyelash formation can be part of lymphedema-distichiasis syndrome, or LD, which is caused by mutation in gene FOXC2.

Today we have a theory of flexible genetic inheritance. Both nature and nurture are important, and we can do things that have an impact on our genetic characteristics. Fetal alcohol and fetal drug syndromes are examples of how we change an individual’s genetic makeup.

A reviewer always has to guard against reviewing the book that he thinks should have been written rather than the book in front of him. Having said this, I offer the following comments:

Moalem deals at length with rare and obscure genetic problems in individuals more than with the generality of human and other life forms’ genetic natures.

He does not specifically mention brain plasticity even though it is implicit in environmental influence on the brain’s development.

He dwells at some length on Mendelian issues, but, for unknown reasons, does not even mention Darwin and his evolutionary theory of chance mutation and survival of the fittest as an explanation of how humans, and other life forms became what they are today.

“Inheritance” has minimal endnotes and no bibliography, but it has an excellent index which makes it easy for the reader to find topics, terms, and ideas.

Despite his necessary use of technical terms, in covering a wide range of epigenetic issues and problems, Moalem writes in a conversational, easy to read, engaging style, which makes what could have been a dry, technical, book on a difficult subject into an understandable and enjoyable experience for the educated general reader.









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