ELU/Science

161

Fall_2002

Buthaina(Ms.)

EfS Chapter 10_Reporting

Directions:

Use the words shown on the box below to fill in the blank spaces in the following report.

inherited	determine	bloom	traits	distinct	significant	applicability
botanist	Genetics	principles	factors	recessive	generation

The Science of Genetics

Most of us take it for granted that we have __________certain characteristics. We might be tall like our father, musical like our mother, brown-eyed like our grandmother. But why is it we inherit some _______and not others? You might think you are very different from your brother or sister, yet other people notice a family resemblance. How can we explain the differences – and the similarities? And how can a dog give birth to a litter of puppies that are all different?

__________ is the branch of science that seeks to __________the answers to these questions, and to discover how plants and animals have developed over the past two billion years. The field of genetics began with the discoveries of a nineteenth century Austrian monk named Gregor Mendel, who was an amateur _________. His unique contribution was that he studied one characteristic at a time to see how it was passed from one generation to another. He performed experiments with red and white flowered garden peas and obtained some interested results.

Mendel took the male cells (pollen grains) from a red flower and placed them on the female cells (pistils) of a white flower (a process called cross-pollination). When the flower produced seeds, he planted the seeds. Then, when the flower began to ________, Mendel observed that instead of the pink flowers or mixture of red and white flowers he expected, all the first ___________ flowers were red.

Next Mendel took the male cells and placed them on the female cells of these same red flowers (a process called self-pollination). Again the flowers produced seeds, and again Mendel Planted them. This second generation produced some red and some white flowers. The interesting part of this was that the ratio of red flowers to white was precisely three to one! Also, there were no pink flowers. Thus Mendel showed that a mixture of characteristics did not blend into something that was in between the two. Rather, the characteristics remained ________ in the next generation.

Mendel concluded that there are certain _______ (later called genes) that determine the color of the plants. He also established that the red factor was stronger or dominant, and the white factor was weaker, or _________. But the recessive factor did not disappear; it only became hidden and sometimes emerged in a later generation (witness: the red flowers produced white flowers). This explains why, for example, two dark-haired parents sometimes give birth to a blond child. Both parents may be carrying recessive genes for blond hair.

Gregor Mendel made genetics into a science. He was able to predict exactly the number and type of plants his experiments would produce. Unhappily for him, Mendel’s work was not recognized in the scientific world until 16 years after his death. Since then, experiments have been performed with numerous traits of plants and animals, which have demonstrated the universal _____________ of Mendel’s findings. The __________ of heredity that Mendel established were ___________ in substantiating Darwin’s theory of evolution.