Gregor Mendel was a monk working in what is now the Czech Republic. In the 1850s and 1860s he carried out breeding experiments on the garden pea, Pisum sativum, and his results are the basis of modern genetics.Peas were a good choice because they grow quickly, produce many seeds, and normally self-fertilise, so Mendel could control which plants were crossed by transferring pollen by hand. He studied seven characteristics that each had two clear forms, for example tall or dwarf stems, round or wrinkled seeds and yellow or green seeds.His method was careful and quantitative:• He started with pure-breeding lines, which always produced offspring like themselves.
• He studied one characteristic at a time before combining two.
• He counted large numbers of offspring and analysed the ratios mathematically.When he crossed pure-breeding tall plants with pure-breeding dwarf plants, all the F1 were tall. When the F1 self-fertilised, the dwarf form reappeared in the F2 in a ratio of about 3 tall : 1 dwarf (787 tall to 277 dwarf).Mendel concluded that each characteristic is controlled by a pair of inherited 'factors' (we now call them genes and their alleles), that one factor can be dominant over another, and that factors are passed on unchanged. His ideas are summarised as the laws of segregation and independent assortment.Mendel published his work in 1866, but it was largely ignored until it was rediscovered in 1900, when chromosomes had been observed.
• He studied one characteristic at a time before combining two.
• He counted large numbers of offspring and analysed the ratios mathematically.When he crossed pure-breeding tall plants with pure-breeding dwarf plants, all the F1 were tall. When the F1 self-fertilised, the dwarf form reappeared in the F2 in a ratio of about 3 tall : 1 dwarf (787 tall to 277 dwarf).Mendel concluded that each characteristic is controlled by a pair of inherited 'factors' (we now call them genes and their alleles), that one factor can be dominant over another, and that factors are passed on unchanged. His ideas are summarised as the laws of segregation and independent assortment.Mendel published his work in 1866, but it was largely ignored until it was rediscovered in 1900, when chromosomes had been observed.