![]() While the P generation was composed of pure line plants, he knew that the F 1 generation was composed of half the genetic information from each plant in the P generation. Mendel pondered, “If one phenotype dominates over another, how can the recessive phenotype even exist in a population?.” This led him to conduct another controlled cross, this time between plants of the F 1 generation. White flowers are recessive to purple flowers in pea plants. In contrast, the phenotype that is masked is known as the recessive phenotype. For flower color, purple dominated over white, meaning if a pure-line, purple-flowered plant is mated with a pure-line, white-flowered plant, all of the resulting offspring have purple flowers. He called these expressed phenotypes dominant, meaning that if there is a mix of two pure lines this phenotype will be expressed. Rather, he found that one of the extreme traits appeared in a cross of different pure lines. Mendel’s results for all of his physical traits did not support the blended inheritance hypothesis. We will focus on his experiment with different flower colors: purple and white. The resulting offspring are the first filial (or F 1 ) generation. ![]() Mendel mated peas representing two extreme “pure line” phenotypes from the P generation. The P generation served as the starting point for his inheritance experiments He collectively called pure line plants the P generation, the parent generation. Mendel's Monohybrid Cross Creating pure linesįrom his controlled self-pollinations, Mendel germinated and grew the “pure line” seeds of plants with several different phenotypes: seed shape, seed color, pod shape, pod color, flower color and stem length. This prediction is supported in the fossil record. Lamarck argued that if this happened from generation to generation, we would see giraffe neck length increase through time. Furthermore, Lamarck suggested that the offspring of the giraffes that stretched their necks would inherit this acquired characteristic. He suggested that the giraffes that were able to stretch their necks the most would be more likely to survive and reproduce (He coined “survival of the fittest,” not Darwin). Lamarck suggested that these early giraffes stretched their necks out to reach leaves in trees during times of drought, individually acquiring a longer neck. Early (now extinct) ancestors of giraffes had considerably shorter necks than modern day giraffes. He used the fossil records of giraffes and their ancestors as the nexus of his argument. This hypothesis was championed by Jean Baptiste de Lamarck. For example if a tall man and a short woman have a child, this hypothesis predicts their child would have a height intermediate relative to her parents.Īnother (non-competing) hypothesis of inheritance was in vogue during Mendel’s lifetime: inheritance of acquired characteristics. The blended inheritance hypothesis suggests that physical traits (or phenotypes ) of offspring are an intermediate of the parents. During Mendel’s time, the most accepted hypothesis of inheritance of physical characteristics was blended inheritance. For example, you hear family and friends comment on how a child is a perfect mix of father and mother, or how a baby has her father’s nose and her mother’s lips. Humans have probably done this since the dawn of time. ![]() Mendel wasn’t the first person to theorize how traits are inherited from generation to generation. Pre-Mendelian Concepts on Inheritance Blended inheritance hypothesis From his experiments with peas, he was able to determine several basic principles of how traits were passed from parents to offspring. Gregor Mendel was an Austrian monk that devoted nearly as much of his life to understanding the nature of heredity as he did in his fraternal duties.
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