Home \ Online Books \ The Creation Explanation

Mendel's Laws

Between 1856 and 1864 Gregor Mendel conducted experiments which led to the discovery of the cardinal principle of heredity.⁶ He worked with pea plants in the garden of his monastery, carefully observing and recording the characteristics of successive generations of pea plants which resulted from the crossing of different varieties. He discovered a mathematical relationship evident in the characteristics of the plants making up the successive generations of pea plants. The basic characteristics he followed were shape, color and size. Mendel noticed that some pea plants were tall, some short; some peas were round, some wrinkled; some peas were green, some yellow.

Mendel found that if he crossbred a round pea with a wrinkled pea, the first generation gave him round peas. If he crossed a yellow pea with a green pea, the first generation gave him yellow peas. The second generation of offspring showed a ratio of three round peas to one wrinkled pea, three yellow peas to one green pea. He reasoned that the characteristics for round peas and wrinkled peas (shape), and yellow peas and green peas (color), were stored in the "memory" of the peas. The characteristics that showed up in the first generation Mendel called dominant, the hidden characteristics, recessive.

Mendel's research results led him to draw the following conclusions:

1. There are definite hereditary units which are responsible for the transmission of characteristics. Mendel called them factors. Now we call them genes.

2. There are two of each type of factor in the mature organism.

3. When the factors differ, only one will be expressed (dominant) while the other will remain latent (recessive).

4. The factors segregate unchanged into the gametes so that each gamete (egg or sperm) carries only one factor of each kind.

5. There is a random union of gametes which results in a predictable ratio of characters in the offspring.

A careful study of the accompanying chart will reveal why crossing pure round-yellow peas with pure wrinkled-green peas results in a first generation which is all round-yellow, whereas the second generation has the different kinds in this ration: 9 round-yellow to 3 round-green to 3 wrinkled-yellow to 1 wrinkled-green.

Mendel's law works for all sexually reproducing organisms. This is why a person might have eye color like one of his grandparents instead of his parents. Most variations within kinds can be explained by this concept. Secondary effects are produced by mutations (discussed below). Several other genetic processes occur which only result in reshuffling of existing genetic information. It should be pointed out that Mendel was fortunate in his selection of characters to study, for the three he chose--plant size and color and shape of peas--are controlled by genes located on three different chromosomes. This means that in the process of mitosis they can be independently assorted. Without independent assortment of characters the nice mathematical ratios would not have shown up in his results.

With the Mendelian view of the laws of heredity, plus the more recently discovered facts about chromosomes and genes, we can understand the basic creation model for genetics. According to the creation model, the "kinds" were established in the beginning and the genetic boundaries set. Mendelian inheritance operating on a gene pool containing more than one form of some of the genes provides for limited variation within kinds, and other processes produce further changes. But human observation and reproducible experiments have yet to demonstrate more than trivial changes compared with those required by evolutionary theory. The facts fit the picture found in the opening chapters of Genesis.

figure 4-4. Mendel's law illustrated. The letter symbols for genes of the peas are as follows: R = round (dominant), w = wrinkled (recessive), Y = yellow (dominant), g = green (recessive). The "gametes" are the sex cells (pollen or eggs).

The actual molecular structures and designs which scientists have discovered to be involved in the genetic law will be our next object of study. These discoveries, resulting from four decades of intense scientific research, constitute on of the most striking accomplishments in the history of science. Such knowledge leads Bible-believing Christians to glorify the Creator for His great wisdom and power. They are amazed that the unbelieving scientists can so easily assume God out of the fantastically complex systems of molecular genetics which they have so recently discovered and which still are shrouded in much mystery and a web of unanswered questions. Let us go on now to a consideration of the basis of genetics in the chromosomes and the molecular structure of genes.

References

6. Ibid., pp. 117-166; Moore and Slusher, (ref. 1), pp. 83-104.