Gregor Mendel discovered the gene.

An Augustinian friar called Gregor Mendel bred pea plants and observing how certain traits were passed on, he effectively discovered the gene.

Continuing the BBC Discovery series Bad Blood this week a key goal of eugenics in the 20th century was to eliminate genetic defects from a population.

You may listen to this program NOW on Demand on the BBC Discovery Page which is available until Tuesday the 21st of February. It will also be broadcast on Sunday the 19th of February in Phuket at 8:30 AM on 91.5 FM and 102.5 FM and Online via the Internet radio portals.

Many countries pursued this with state-led programmes of involuntary sterilisation, even murder.

We unpick some of the science behind this dark history and consider the choices and challenges opened up by science today.

An Augustinian friar called Gregor Mendel

In the mid-19th century, an Augustinian friar called Gregor Mendel made a breakthrough.

By breeding pea plants and observing how certain traits were passed on, Mendel realised there must be units – little packets – of information determining characteristics.

He had effectively discovered the gene.

His insights inspired eugenicists from the 1900s onwards. If traits were passed on by specific genes, then their policies should stop people with ‘bad’ genes from having children.

Mendel’s ideas are still used in classrooms today – to teach about traits like eye colour.

But the eugenicists thought Mendel’s simple explanations applied to everything – from so-called ‘feeblemindedness’ to criminality and even pauperism.

Today, we recognise certain genetic conditions as being passed on in a Mendelian way.

Achondroplasia – which results in short stature – is one example, caused by a single genetic variant. We hear from Professor Tom Shakespeare about the condition, about his own decision to have children despite knowing the condition was heritable – and the reaction of the medical establishment.

We also explore how genetics is taught in schools today – and the danger of relying on the Mendel appealingly simple but misleading account.

Contributors: Dr Brian Donovan, a senior research scientist at BSCS, Prof Tom Shakespeare, a disability researcher at the London School of Hygiene and Tropical Medicine; and Dr Christine Patch, a principal staff scientist in Genomic Counselling in the Society and Ethics Research Group, part of Wellcome Connecting Science.

WikipediaSays about Mendel:

Mendel, known as the “father of modern genetics”, chose to study variation in plants in his monastery’s 2 hectares (4.9 acres) experimental garden.

After initial experiments with pea plants, Mendel settled on studying seven traits that seemed to be inherited independently of other traits: seed shape, flower color, seed coat tint, pod shape, unripe pod color, flower location, and plant height. He first focused on seed shape, which was either angular or round. Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, the majority of which were pea plants. 

This study showed that, when true-breeding different varieties were crossed to each other (e.g., tall plants fertilized by short plants), in the second generation, one in four pea plants had purebred recessive traits, two out of four were hybrids, and one out of four were purebred dominant.

His experiments led him to make two generalizations, the Law of Segregation and the Law of Independent Assortment, which later came to be known as Mendel’s Laws of Inheritance.

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