In 1866, when Gregor Mendel was experimenting in his monastery garden with different varieties of pea plants, he discovered that when tall (TT) plants were crossed with other tall (TT) plants, the offspring were also always tall.
This is not what Mendel expected to find – when he started doing this experiment he thought the plant’s height could be influenced by environmental factors or by which parent it came from. However, when you cross two identical peas and they both have a genetic mutation for being tall – then all their children will also have this genetic mutation and so will all their grandchildren too!
This means that if you want your kids to grow up to be as tall as you are then you should be careful about who you date.
The first thing Mendel did when he discovered this was cross tall (TT) plants with short (tt) plants instead. When the offspring of these two different types of pea plants were grown, they turned out not to be purely one type or another – some were tall and others were short like their parents!
But now that we know how it all works thanks to Gregor Mendel’s experiments results, maybe we should take a more detailed look at his methods for knowledge sake rather than just because our children are being too picky about which parent they want us dating…maybe?
when Mendel crossed tall (tt) plants with tall (tt) plant the offspring
how Mendel’s methods work when he crossed tall (TT) plants with short (tt) plants
what Mendel discovered when growing the ‘tall’ and ‘short’ pea plant hybrids.
Mendel’s experiments with the tall and short pea plants showed that when he crossed them together they became heterogeneous, meaning there were some taller than others but not strictly one type or another. This explained his earlier observation of inconsistency from crosses between different types of pea plants because there was a difference in gene expression as well as the environment imposed on their growth rates compared to those grown under identical conditions. This is called genotype x environment interaction.
Mendel never experimentally tested for dihybrid inheritance where both genes are inherited so it’s unclear which genetic marker would be dominant if this were the case – essentially Mendel did not know how many alleles an offspring inherits during meiosis (cell division).
Mendel’s Inconsistent Crossing Between Tall (TT) Plants with Tall (TT) Plants Resulted in Hybrid Offspring. Mendel had an earlier observation of inconsistency when he crossed different types of pea plants, so when he cross tall plants with tall plants the offspring became heterogeneous and this explained his earlier observations. This is called genotype x environment interaction because there was a difference in gene expression as well as environment imposed on their growth rates that were not identical to each other compared to those grown under these same conditions. He never experimentally tested for dihybrid inheritance where both genes are inherited, but it would be unclear which genetic marker would be dominant if this were the case – essentially Mendel did not know how to cross one trait with another.
In his experiments, Mendel crossed tall plants (TT) with tall plants and got hybrid offspring. This is how he arrived at the idea that traits are inherited from one parent or the other in a specific way: dominant to recessive.
when Mendel crossed tall (tt) plants with tall (tt) plant the offspring
this is how Mendel came up with ideas about the inheritance of traits in pea plant crosses
attributes inherit from parents only through single combinations
When Mendel crossbred two distinct varieties of peas, it was found that given certain conditions they will always produce an identical ratio of four possible types of pea pod seeds. In these cases, we can say without any doubt that the two varieties of peas are homozygous. The reason for this is that the variety with purple flowers and yellow pods (PpY) will only produce one type of pea pod seed, while the variety with green flowers and green pods (GgG) will always produce three types of seeds.
when Mendel crossed tall plants with tall plants
given certain conditions they should always create identical ratios four possible types of pea plant seeds: PpY, GgG, ppGG & ppyyy
because in the case with purple flower yellow pod there would be no variation at all – so any other combination would also give you the same result because those are “dominant” traits
