Genetic Screening

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GENETIC SCREENING

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What is genetic screening?

One of the fastest moving fields in medical science.

A technique to determine the genotype or phenotype of an organism.

It is often used to detect faulty or abnormal genes in an organism.

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Some examples of genetic tests

Prenatal screening

Newborn screening

Carrier screening

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Prenatal Screening

This can detect a disorder before a baby is born.

An ultrasound test is used to determine if the fetus is at a high or low risk from a genetic disorder.

Disorders are diagnosed by examining a small amount of fetal cells. This carries a small risk to the fetus.

If diagnosed early in the pregnancy, there is still the possibility of abortion.

Prenatal screening is sometimes seen as controversial.

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Newborn Screening

Newborns are tested for diseases and early diagnoses allows for immediate treatment.

A blood sample is tested for genetic disorders.

In most of the USA, newborn screening is mandatory, unless parents have a religious objection to it.

Sometimes residual blood samples are used for genetic research, as long as the samples are kept anonymous.

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Carrier Screening

This involves testing prospective parents for diseases that they show no symptoms of, but may carry a recessive gene for.

A blood sample or cheek cell sample is analysed to determine whether either parent carries a faulty gene.

If both parents carry a specific faulty gene, the chance of the fetus receiving the gene from both parents is 25%, and the chance of being a carrier is 50%.

If both parents carry a faulty gene, they may decide to have prenatal testing on the fetus.

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Other types of screening

Preimplantation screening: Screening embryos fertilised by IVF before they are implanted into the uterus.

Presymptomatic screening: Screening to predict adult-onset diseases such as Huntington’s disease.

Presymptomatic screening: Screening to estimate the risk of developing cancer or Alzheimer’s disease as an adult.

Forensic/Identity testing: Screening to eg. determine the father of an individual (paternity test).