Last week, I explained that most individuals have 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes (for a total of 46 chromosomes all together). But a subset of people has chromosomal abnormalities in the form of an extra chromosome or a missing chromosome. Most chromosome abnormalities are fatal and result in early miscarriages, but some abnormalities are survivable. One of the most common survivable chromosome abnormalities is Down syndrome, in which there are three copies of chromosome 21 instead of two (known as a trisomy). The extra chromosome copy causes physical, mental, and developmental abnormalities. There are…
Comments closedMonth: July 2020
Last week we saw how the complex interplay of genetics and environment has impacted the inheritance of sickle-cell anemia. This week, I want to talk about a special subset of inherited diseases called sex-linked disorders. One of the most common sex-linked disorders is Duchenne muscular dystrophy (DMD), a debilitating muscular disorder linked to the X-chromosome. Sex-linked disorders, like DMD, come from genes in the sex chromosomes (X and Y in humans). Sex chromosomes are responsible for determining an individual’s biological sex, XX for female, XY for male (although there are other less common combinations that come from chromosomal aberrations—we’ll talk…
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Last week, I discussed the genetic basis of cancer risk, specifically breast cancer. This week I want to start talking about direct genetic diseases, starting with a disease that has an interesting connection with malaria: sickle-cell anemia. Sickle-cell anemia affects millions of people worldwide, and it is particularly common in people with African or Mediterranean ancestry. Individuals with two sickle-cell disease (SCD) genes (one from their mother and one from their father) develop sickle-cell anemia, which causes their red blood cells to become warped and “sickle” shaped. These sickle cells are stiff and they tend to build up in the…
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The last few weeks, I’ve discussed how the efforts of the human genome project and next-generation sequencing have contributed to significant progress in the field of personalized medicine. Identifying the precise genetic basis of a disease can help scientists understand how the disease manifests, can help doctors diagnose and treat patients earlier, and could potentially unlock the ability to remove the disease through genetic editing. Many diseases have a genetic basis and not all of them are fully understood. Within this series, I will endeavor to uncover some of what scientists have learned about genetic diseases, disorders, and risk factors.…
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After the Human Genome Project was completed in 2003, scientists were looking for faster, cheaper, and more efficient sequencing methods than the Sanger Sequencing utilized in the 13-year project. In 2005, researchers at 454 Life Sciences (later acquired by Roche) developed the first Next-Generation Sequencing method called pyrosequencing. Since then, many other companies have developed their own Next-Generation Sequencing methods. The main Next-Generation Sequencing methods developed in the last two decades include a newer, improved pyrosequencing called Roche 454, Illumina’s Solexa Genome Analyzer series, and Ion Torrent sequencing. As scientists continue to develop newer and more efficient sequencing methods, it…
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