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Topic section: Tracing your ancestors could save your life
TOPIC SECTION:
Tracing your ancestors could save your life
Amateur genealogists can sometimes find patterns of health problems in their family tree, such as a prevalence of heart diseases or certain cancers. B

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Watson and Crick’s DNA molecular model, 1953. Some inherited conditions are the result of a small number of changes in this DNA sequence, known as genetic mutations.
Credit: Science Museum/Science & Society Picture Library
eing aware of these patterns, they can take steps to avoid them by, for instance, taking more exercise. These com
Normal babies fail to thrive and eventually become blind, deaf, mentally disabled and paralysed
mon health problems cannot be linked to a specific genetic defect. Nonetheless, some inherited conditions (‘genetic diseases’) are the result of a small number of genetic mutations. They can often be traced back to a single individual with this defect who passed the disease on to their descendants. As soon as a condition of this type is identified, it is important to discover who may be affected so that they can be contacted and if necessary treated. Family history can be very helpful in this situation. For instance, Ellis-van Creveld syndrome can be traced back to Samuel King, who arrived in America in 1744; and hereditary sensory neuropathy was taken to Australia by Hannah Blair in 1800.

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The DNA sequencer can be used to identify changes in the DNA sequence known as genetic mutations, which may result in genetic disease.
Credit: Science Museum/Science & Society Picture Library
Some diseases have spread beyond a single family or even an extended clan, and have become linked to a large ethnic group.In the past, at least, Jews of eastern European origin (the Ashkenazi) tended to marry within their own community and because of this they are prone to several genetic conditions. One important example is Tay-Sachs disease, which is caused by the absence of a crucial enzyme found in brain cells. Appar
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A sequencing chromatograph showing a DNA sequence, from the human genome-mapping project.
Credit: Science Museum/Science & Society Picture Library
ently normal babies fail to thrive and eventually become blind, deaf, mentally disabled and paralysed. One in 27 American Ashkenazi Jews is a carrier of the genetic defect compared with one in 250 of the non-Jewish population of the United States.

Not all genetic mutations are a result of inbreeding, or without redeeming value. The sickle-cell trait affects Africans (and people of African descent) and people from the Mediterranean disproportionately. Although it can bring about illnesses, such as sickle cell anaemia, sickle-cell trait probably evolved as a partial protection against malaria, which is endemic in western and central Africa.

 
 
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Topic section: One big family
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Scientists have attempted to reconstruct the movement of different groups and the development of modern cultures. It appears we are all descended from a small group of early people, the mothers and fathers of all living human beings.  > more

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Topic section: To find an ancestor, get a DNA test
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Using genealogy, we can sometimes track our ancestors over a couple of centuries. Genetics can do much more: it can link people who died thousands of years ago to their modern-day descendants.  > more

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Topic section: DNA and ethnic identity
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When we combine genetics with archaeology, linguistics and history, we can go even further back, to the very origins of human civilisation.  > more
 
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