Hello All AIPMT Biology Aspirants, next important topic in queue is Mendel’s Success Story.
Earlier, plant biologists also produced hybrids but they saw puzzling results and were not able to interpret them correctly. Mendel used mathematical techniques to analyze his crosses, which was ahead of that time and people were not able to understand his results. So his results remained unnoticed for 35 years.
- Mendel worked with the common garden pea plant, Pisum sativum in the garden of the monastery. He chose the pea plant for at least four reasons:
(1) The garden pea was easy to cultivate and had a relatively short life cycle. So he could grow several generations in a single year and interpret results quickly.
(2) The plant had large no. of pure characteristics such as flower color and pea texture.
(3) Self-fertilization takes place automatically in pea, within an individual flower as both male and female sexual organs are enclosed within each pea flower.
- It is also possible to prevent self-fertilization by removing a flower’s male part “stamen” before fertilization (process known as Emasculation), & then introduce pollen from a desired strain, thus performing cross pollination.
- Bagging of female part of flower, after emasculation is done to prevent any unwanted pollen to do fertilization. Bagging is simply covering the female part of the flower by butter paper or polythene.
- Mendel controlled mating of pea through emasculation and bagging.
(4) Earlier, plant biologists had also produced hybrids of pea plant, so he could expect to get desirable traits among offspring.
Mendel was successful in his experiments because:
- He chose that characteristics of pea plant which have two easily differentiated forms, such as white versus gray seed coats, round versus wrinkled. He avoided characteristics that display a range of variation.
- He adopted an experimental approach and interpreted his results by using mathematics.
- He used both qualitative and quantitative approach to interpret results, earlier biologists used only qualitative.
- Mendel formulated hypotheses based on his initial observations and then conducted additional crosses to test his hypotheses. He used the scientific methods to test his hypotheses.
- He followed the inheritance of individual characteristics for several generations conducting his experiments for 10 years, before attempting to write up his results.
- He counted the numbers of offspring exhibiting each trait in each succeeding generation.
Mendel was trying to solve these two theories:
At the time, Mendel started doing his experiments; two theories had emerged to explain the results of breeding experiments:
- Blending inheritance: It states that traits observed in parents blend together to form traits observed in their offspring. As a result, an offspring’s traits are intermediate between the parents’s traits. Traits lose their individuality after blending and could never be separated.
- Particulate inheritance: It states that each trait maintains its distinct nature during and after fertilization. Traits do not lose their individuality in the offspring, no matter what would be the trait of offspring.
These were the two competing theories; Mendel’s work clearly supported the particulate theory.