Gregor Mendel was a monk who lived in what we now know as Czech Republic. He enjoyed gardening, and one day he became curious about the fact that some pea plants were tall and others were short; some were yellow, and some were green etc. Mendel decided to check this out, so he forced a tall pea plant and a short pea plant to mate with each other by collecting the pollen from one and placing it in the pistil of the other. He made sure that neither plant mated with its own type. The pea plants produced from that experiment were tall - not of medium height like you would expect to get by mixing a tall and a short plant, but tall. After many more experiments, Mendel then proceeded to mate the offspring of the original pea plants with each other. Curiously, three out of four pea plants were tall, but one was short.
From these experiments, Mendel became the first investigator of genetics. The parent plants were both purebred short and tall pea plants. When they were mated to produce F1 offspring, each parent plant passed on one allele. (An allele is a form of a gene that changes is in charge of changing only one aspect of a trait.) The tall plant passed on an allele for being tall, and the short one passed on an allele for being short. If the dominant or tall allele is represented by a capital T and the short or recessive allele is represented by a lowercase t, then the alleles for the F1 offspring looked like Tt. What Mendel began to discover was that a recessive allele will only be visible in an organism if it is the only allele for that trait present. If there is one tall and one short allele, then the plant will be tall. If there are two tall alleles, then the plant will be tall. The only way the plant will be tall is if it has two short alleles. This is why none of the F1 offspring were able to be short, because they always had one short and one tall allele. However, when Mendel mated F1 offspring with each other to make F2 offspring, he noticed something strange: approximately 1 in every 4 pea plants created by two F1 offspring were short. This was because, although all the F1 offspring were tall, they each had one short and one tall allele. When two of them were mated, there was a small possibility that, out of Tt and Tt alleles, a seed would be generated that would be tt.
The experiment we did was that we had a bowl full of yellow and black balls to represent peas. The ratio of yellow to black peas was uneven, and there were many more yellow peas than black ones. We took turns pulling out four "peas" from the bowl and recorded our data. We did this 20 times. Each time, we wrote down how many yellow and how many black balls we pulled out of the bowl, and then we averaged our results. In the end, we pulled out 2.85 yellow peas and 1.15 black peas, which averages down to three yellow and one black pea. Mendel, on the other hand, would have had to do this experiment MANY more times, since he did not know any of the things we do now about genetics. Mendel probably had to plant 50 to 100 pea plants to be sure of his data.
From these experiments, Mendel became the first investigator of genetics. The parent plants were both purebred short and tall pea plants. When they were mated to produce F1 offspring, each parent plant passed on one allele. (An allele is a form of a gene that changes is in charge of changing only one aspect of a trait.) The tall plant passed on an allele for being tall, and the short one passed on an allele for being short. If the dominant or tall allele is represented by a capital T and the short or recessive allele is represented by a lowercase t, then the alleles for the F1 offspring looked like Tt. What Mendel began to discover was that a recessive allele will only be visible in an organism if it is the only allele for that trait present. If there is one tall and one short allele, then the plant will be tall. If there are two tall alleles, then the plant will be tall. The only way the plant will be tall is if it has two short alleles. This is why none of the F1 offspring were able to be short, because they always had one short and one tall allele. However, when Mendel mated F1 offspring with each other to make F2 offspring, he noticed something strange: approximately 1 in every 4 pea plants created by two F1 offspring were short. This was because, although all the F1 offspring were tall, they each had one short and one tall allele. When two of them were mated, there was a small possibility that, out of Tt and Tt alleles, a seed would be generated that would be tt. The experiment we did was that we had a bowl full of yellow and black balls to represent peas. The ratio of yellow to black peas was uneven, and there were many more yellow peas than black ones. We took turns pulling out four "peas" from the bowl and recorded our data. We did this 20 times. Each time, we wrote down how many yellow and how many black balls we pulled out of the bowl, and then we averaged our results. In the end, we pulled out 2.85 yellow peas and 1.15 black peas, which averages down to three yellow and one black pea. Mendel, on the other hand, would have had to do this experiment MANY more times, since he did not know any of the things we do now about genetics. Mendel probably had to plant 50 to 100 pea plants to be sure of his data.
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