Genetics Pop Quiz #1: Genetic = Inherited?
Question #1 - When a characteristic is genetic, is it also inherited?
Question #2 - When a characteristic is inherited, is it also genetic?
Answers
1. NO. While some genetic mutations are transmitted from parent(s) to child, mutations can also occur spontaneously and at random. Common causes of mutations include smoking, radiation, and excessive sun exposure. Other mutations may result simply from the constant replication of DNA that occurs in our bodies. Replicating DNA is complex and mistakes happen. Some of the mistakes can eventually lead to disease.
I often hear people say, “I can’t believe he had colon cancer. I read that cancer is genetic but nobody in his family has had cancer!”
All cancers are caused by genetic mutations, but not all these mutations are shared with family members. About 15-20% of colon cancer patients have family members who are also affected by the disease, but 80-85% of patients do NOT have a family history.
Studying families that seem to have clusters of the disease helps to identify genes which may lead to a better understanding of the genetic mechanism underlying cancer development. Recently, researchers discovered that a mutation in the transforming growth factor beta receptor1*6A (TGFRB1*6A) gene may be responsible for some forms of hereditary colon cancer.
Altered genes trigger all cancer. “Most cases of breast, ovarian and colon cancers are caused by damage to the genes that builds up over a lifetime, but some people are born with a high risk of the disease,” explains Dr. Boris Pasche. “When inherited, the TGFRB1*6A gene makes people susceptible to having certain cells grow and divide uncontrollably, which may contribute to cancer development.” (Medical News Today, May 3, 2005)
2. NO. Not all inherited characteristics are caused by genes.
One common example given in human genetics classes is the observation that some families have an above average number of doctors in their families with many grandparents, aunts and uncles, parents, cousins, and children all in the medical profession. Analyzing such a family tree for the “medical profession trait” would seem to show that the trait is inherited. Maybe a gene for higher intelligence or a gift of memory is transmitted from generation to generation, but the specific “medical profession trait” is most likely cultivated by family environment.
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