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Gregor Mendel
Gregor Mendel was born in 1822 in what is today the northeastern part of the Czech Republic. At 21 years of age he entered an Augustinian monastery in Brno, the second largest city in Czech. From there he went on to study in Vienna (Austria) and then returned to teach in Brno. Between 1856 and 1863 Mendel experimented with pea plants, looking at inheritance of traits. In this period he took notes on 29,000 pea plants that he cultivated in the monastery’s garden.
The results of his study showed that when large numbers of offspring were analysed for particular traits, one in four had dominant genes, one in four had recessive genes, and two in four had mixed dominant/recessive genes.
When Mendel took a purebred white flowering pea, and crossed it with a purebred purple flowering pea, all the resulting (second generation) pea plants had purple flowers. Mendel wondered what had happened to the “factor” that caused white pea flowers. He found his answer when he crossed his second generation peas, as one in four of their offspring was white flowering, even though all the second generation parents were purple-flowered. He realized that purple flowers were dominant to white flowers, much like we now know a black coat of hair is dominant in Labrador dogs. He also realized that purple flowered peas could be hiding a gene that codes for white flower colour behind the dominant purple-coding gene.
Mendel went on to state that each individual has two factors for each trait, one from each parent. The two factors may or may not contain the same information. If the two factors (one coming from each parent) are identical the individual is called homozygous for the trait. If the two factors (again one from each parent) have different information, the individual is called heterozygous.
Once this information was known, it became possible to predict the proportion of offspring that would show a particular trait.
Mendel published his findings in 1866, but they were completely ignored. An eminent botany professor of the time stated that he was unimpressed, and Mendel’s bishop was unhappy that monastery funds had been used to construct a greenhouse to facilitate his work. The bishop of Prague suggested that Mendel should cease his work, and in 1868 Mendel assumed the position of Abbot and confined himself mainly to administrative duties. Mendel died in 1884 and after his death, the new abbot burned all the papers in Mendel's collection.
In 1900, Mendel’s work was rediscovered by way of the 1866 publication. Mendel's experiments were copied and his results were tested. Genetic linkages were quickly worked out. Biologists flocked to the theory because of its logic and simplicity. His 1866 publication is now considered a masterpiece, thanks to his careful attention to procedure and detail. As a result, Mendel's work had a huge impact on the world of genetics, and today the principles he unearthed are known as Mendel's Laws of Heredity.
Here is a little genetics test that you can do in your family:
Are your earlobes free-hanging or attached to your head?
Some people have earlobes than hang, and some people don’t. (See sketch).
Free hanging earlobes are dominant and attached earlobes are recessive.
This means that if you have attached earlobes, you inherited recessive genes from both your parents.
This could happen in three ways:
1. Both your parents have attached earlobes. (They both carry only recessive genes). You and all your brothers and sisters will have attached earlobes.
2. One parent has attached earlobes and one has free-hanging earlobes. (The parent with attached earlobes carries only recessive genes, and the parent with free-hanging earlobes carries one dominant and one recessive gene). There is a 50/50 chance that you and your brothers and sisters will have either attached earlobes or free-hanging earlobes.
3. Both parents have free-hanging earlobes. If this is the case, both your parents must be carrying a dominant and recessive gene for this trait, and there is only a 25% chance that you would end up with attached earlobes. There is a 75% chance that your brothers and sisters have free-hanging earlobes.
On the other hand, if you have free hanging earlobes, like in the sketch below, you could have inherited the dominant gene from one of your parents, or from both. If you can find out whether your parents, spouse and children’s earlobes are attached or free-hanging, you should be able to figure out your genetics for this trait. A little puzzle for over the Christmas:
Winter Competition:
You will need an adult to help:
Both of your parents have free-hanging earlobes but yours are attached. Your spouse or partner has free-hanging earlobes. Your spouse’s mother has attached earlobes, while your spouse’s father has free-hanging earlobes.
What are the chances that your first child will have attached earlobes?
A: 100% B: 50% C: 25%
Answers to:
Ear competition,
The Apple Farm, Moorstown, Cahir, Co. Tipp.
Closing date: January 30th, 2009
Autumn competition winners:
Sinead, Horse & Jockey (€20.00 Easons voucher)
Jack Caplice, Fermoy (€10.00 Apple Farm voucher)
Brigid, Mullinahone (€10.00 Apple Farm voucher)