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Tag: Genetic Definitions III

Proactive Medical Testing Part III – 23 and Me and A Couple of Things

March 15, 2019 Sarah

What a difference 5 years make! Five years ago I had cancer and genetic testing was expensive, not covered by insurance and not commonly used.

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Proactive Medical Genetic Testing with 23 and Me, Invitae and X Code for Life: Part 1 Deciding to Test.

February 20, 2019 Sarah

What is Genetic Testing? Genetic testing analyzes your genes, which are the instructions in your DNA. Your genes help determine your physical traits. It looks

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Genetic Definitions III

NUCLEUS:
The structure in a cell which contains the genetic material.

PHENOTYPE:
The physical and/or biochemical characteristics of a person, an animal or other organism which are determined by their genetic make-up and/or environment.

POLYGENIC:
A condition or characteristic that is caused by many different genes acting together.

POLYMORPHISMS:
Changed genes, DNA sequences or chromosome structures which occur naturally in the population and do not cause any harm to the individual.

PREDICTIVE TESTING:
A form of genetic testing performed on a person with a family history of a particular genetic condition, but who does not have any symptoms of the condition at the time of testing. This testing determines if that person has inherited the mutation (present in their family). If testing for this mutation reveals that it is present in the person, then they have an increased predisposition to developing the condition that was tested for. The detection of a specific mutation does not necessarily mean the individual will definitely develop the condition. Familial breast cancer is an example of a condition where predictive testing is used.

PREDISPOSITION:
A situation in which a person, due to their inherited genetic make-up, may have a particular susceptibility to a condition if exposed to the correct environmental triggers.

PRESYMPTOMATIC TESTING:
A form of genetic testing performed on a person with a family history of a particular genetic condition, but who does not have any symptoms of the condition at the time of testing. This testing determines if that person has inherited the mutation (present in their family). If testing for this mutation reveals that it is present in the person, then they will most likely develop symptoms of the genetic condition it causes at some stage of their life. Huntington disease is an example of a genetic condition where presymptomatic testing is used.

RECESSIVE:
Every cell contains two copies of each gene. Each gene contains the information for a particular gene product, such as a protein. If a gene is mutated, the gene no longer codes for the gene product. Where an individual has one gene copy or allele mutated and the other copy ‘correct’, the cell will only be producing half the amount of gene product. If this does not result in any condition for the individual, the mutation is described as being hidden or ‘recessive’ to the correct copy of the gene. An individual with this genetic constitution is said to be a ‘carrier’ of a recessive gene mutation. For a recessive gene mutation to result in a particular characteristic or a condition, both copies of the genes must be mutated.

RECURRENCE RISK:
The risk that an inherited condition will occur again in a family.

SENSITIVITY:
The ability of a test to detect the presence of a genetic condition or a mutation when it is truly present.

SHORT TANDEM REPEATS (STRs):
Multiple copies of a short, identical DNA sequence repeated in tandem. The pattern of different numbers of STRs at certain sites on the chromosomes may be used to create a DNA pattern or DNA fingerprint that is as unique as possible for each person.

SINGLE NUCLEIOTIDE POLYMORPHISM (SNP):
A DNA sequence variation that involves a change in a single nucleotide. Variations in the genetic code at the level of one nucleotide may be useful in certain applications such as assessing the patterns of inheritance via genetic linkage studies, or forensic DNA testing or DNA fingerprinting.

SUSCEPTIBILITY GENE:
A gene in which, if there is a change or mutation, increases an individual’s susceptibility or predisposition to a certain disease or condition. When such a gene change is inherited, there is a greater likelihood that symptoms will develop, but this is not certain.

TELOMERE:
The terminal or end segment of each chromosome arm.

THYMINE (T):
One of the four basic building blocks (nucleotide bases) that makes up the genetic code (DNA). It is represented by the letter T.

 

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