Number of contrasting traits chosen by
Mendel for his work which determine a
phenotypeother than colour are
(1) 1
(2) 2
3)3 4)4
Answers
Answer:
Gregor Mendel was born in the district of Moravia, then part of the Austro-Hungarian Empire. At the end of high school, he entered the Augustinian monastery of St. Thomas in the city of Brünn, now Brno of the Czech Republic. His monastery was dedicated to teaching science and to scientific research, so Mendel was sent to a university in Vienna to obtain his teaching credentials. However, he failed his examinations and returned to the monastery at Brünn. There he embarked on the research program of plant hybridization that was posthumously to earn him the title of founder of the science of genetics.
Mendel’s studies constitute an outstanding example of good scientific technique. He chose research material well suited to the study of the problem at hand, designed his experiments carefully, collected large amounts of data, and used mathematical analysis to show that the results were consistent with his explanatory hypothesis. The predictions of the hypothesis were then tested in a new round of experimentation.
Figure 2-2. One of the techniques of artificial cross-pollination, demonstrated with the Mimulus guttatus, the yellow monkey flower.
Figure 2-2
One of the techniques of artificial cross-pollination, demonstrated with the Mimulus guttatus, the yellow monkey flower. To transfer pollen, the experimenter touches anthers from the male parent to the stigma of an emasculated flower, which acts as the (more...)
Other practical reasons for Mendel’s choice of peas were that they are inexpensive and easy to obtain, take up little space, have a short generation time, and produce many offspring. Such considerations enter into the choice of organism for any piece of genetic research.
Go to:
Plants differing in one character
Mendel chose seven different characters to study. The word character in this regard means a specific property of an organism; geneticists use this term as a synonym for characteristic or trait.
For each of the characters that he chose, Mendel obtained lines of plants, which he grew for two years to make sure that they were pure. A pure line is a population that breeds true for (shows no variation in) the particular character being studied; that is, all offspring produced by selfing or crossing within the population are identical for this character. By making sure that his lines bred true, Mendel had made a clever beginning: he had established a fixed baseline for his future studies so that any changes observed subsequent to deliberate manipulation in his research would be scientifically meaningful; in effect, he had set up a control experiment.
Two of the pea lines studied by Mendel bred true for the character of flower color. One line bred true for purple flowers; the other, for white flowers. Any plant in the purple-flowered line—when selfed or when crossed with others from the same line—produced seeds that all grew into plants with purple flowers. When these plants in turn were selfed or crossed within the line, their progeny also had purple flowers, and so forth. The white-flowered line similarly produced only white flowers through all generations. Mendel obtained seven pairs of pure lines for seven characters, with each pair differing in only one character (Figure 2-3 ).