Gregor Mendel:
Inheritance is the passing on of particular genes from parents to offspring. Little was known about the principles of inheritance until an Austrian monk named Gregor Mendel conducted several experiments in 1865, to try to discover inheritance patterns. Mendel was a well educated man and he spent ten years researching in order to come up with his two principles of inheritance. These are:
- Many characteristics that are hereditary are controlled by genes, and these factors occur in pairs.
- During gametogenesis, these genes separate ensuring that each gamete only receives one set of genes. The gametes then combine during fertilization, allowing for different combinations of genes to be created.
Although he published a paper on his findings, Mendel's results were ignored by the scientific community until 1900, when considerable advancements were being made in the field of cytology.
Mendel's experiments were conducted using the common garden pea, or Pisum. He chose this plant because they were inexpensive, displayed a large amount of differing characteristics and could practically be sown year-round. In the end, he selected seven characteristics which he wished to study. He then ensured that all the plants in the experiment were homozygous/pure-breed (if bred amongst themselves, would result in each generation having the same characteristic). For example, he would only cross pure-breed round seed shapes with pure-breed wrinkled seed shapes. He then began to cross-breed these plants. From his experiments, he discovered that the F1 generation would only resemble one of its parents. This was surprising to Mendel, given that the offspring contained genetic information from both parents - they were heterozygous. For example, all the peas had a coloured seed-coat, despite the fact that they contained the allele for both traits. He therefore concluded that only one pair of contrasting characteristics appeared in the offspring. He referred to this characteristic as the dominant trait because it masked the effects of the other characteristic (recessive trait).
He then cross-bred the hybrid plants, resulting in a second generation of plants. The experiment resulted in a ratio of 3:1 - approximately 75% of offspring exhibited the dominant trait, while the other 25% displayed the recessive characteristic. From this, he came to the conclusion that hereditary factors do not change as they are passed down from generations. He therefore reasoned that each pea plant under study must have had only two genes for each characteristic that was under study. He put forth this theory as he knew that during the formation of gametes, genes separate to ensure that each gamete created receives at least one gene from each trait. However, due to fertilization, each offspring receives one gene from each parent for the characteristic in question.
- Many characteristics that are hereditary are controlled by genes, and these factors occur in pairs.
- During gametogenesis, these genes separate ensuring that each gamete only receives one set of genes. The gametes then combine during fertilization, allowing for different combinations of genes to be created.
Although he published a paper on his findings, Mendel's results were ignored by the scientific community until 1900, when considerable advancements were being made in the field of cytology.
Mendel's experiments were conducted using the common garden pea, or Pisum. He chose this plant because they were inexpensive, displayed a large amount of differing characteristics and could practically be sown year-round. In the end, he selected seven characteristics which he wished to study. He then ensured that all the plants in the experiment were homozygous/pure-breed (if bred amongst themselves, would result in each generation having the same characteristic). For example, he would only cross pure-breed round seed shapes with pure-breed wrinkled seed shapes. He then began to cross-breed these plants. From his experiments, he discovered that the F1 generation would only resemble one of its parents. This was surprising to Mendel, given that the offspring contained genetic information from both parents - they were heterozygous. For example, all the peas had a coloured seed-coat, despite the fact that they contained the allele for both traits. He therefore concluded that only one pair of contrasting characteristics appeared in the offspring. He referred to this characteristic as the dominant trait because it masked the effects of the other characteristic (recessive trait).
He then cross-bred the hybrid plants, resulting in a second generation of plants. The experiment resulted in a ratio of 3:1 - approximately 75% of offspring exhibited the dominant trait, while the other 25% displayed the recessive characteristic. From this, he came to the conclusion that hereditary factors do not change as they are passed down from generations. He therefore reasoned that each pea plant under study must have had only two genes for each characteristic that was under study. He put forth this theory as he knew that during the formation of gametes, genes separate to ensure that each gamete created receives at least one gene from each trait. However, due to fertilization, each offspring receives one gene from each parent for the characteristic in question.