Jonathan Paul Loomis

November 2, 1998

TA: Heather Emmitte

This laboratory exercise dealt with genetics and inheritance as discovered by the Czechoslovakian Monk Gregor Mendal. Our principal goal was to recreate his famous experiments on plants in which he discovered the phenomena of dominant and recessive genes.

The purpose of this laboratory experiment was to rediscover the phenomena of dominant and recessive genes using plants (as did Mendel), and more specifically to note that the dominant genes will appear about 75% of the time, and the recessive about 25% of the time, given that the parent plants are heterozygous. A further purpose was to note that chlorophyll is not the only color giving pigment in plants, but that it is the dominant one, accompanied by many others.

I predicted that our coin toss experiment would yield an even outcome between heads and tails. I predicted that our plants would produce 75% green plants, and 25% albinos, both in my personal planting, and in the class' overall outcome. I predicted that our chromatography paper would display a variety of lines, both for the albinos, as well as for the regular green plants.

The following is a list of materials used in this lab:

• Coins
• Potting soil
• Plastic trays
• Corn seeds (genus Zea mays)
• HO
• Plastic bags
• Pestle and mortar
• Petroleum ether
• Cheesecloth
• Pipet
• Chromatography paper
• Pencil
• Millimeter ruler

The procedure of this laboratory exercise was the same as that outlined in the laboratory manual, with a few exceptions. We actually performed the coin experiment that in the manual is only described. The instructor also ran a control leaf from a random tree found on campus with gave similar results to those dominant corn plants we experimented on.

H=heads (dominant)

H=tails (recessive)

HH - 2

Hh - 7

hh - 6

This experiment ended up being slightly unbalanced, with there being almost as many recessives appearing as there were dominants.

Personal results

Of the 20 seeds I planted:

My results did produce a significant deviation.

Class results:

Note that my results appear as #13.

The albino run that we did produced no indication lines on the chromatography paper.

The dominant green run we did appeared as follows:

The distance from the start to the front was 6cm.

Results from the dominant run:

This laboratory exercise led me to two conclusions. First, although after many tests of a particular experiment the results will approach their statistically predicted ratios, at first they will often be unbalanced, as in our coin toss experiment. Second, I learned that chlorophyll is not the only pigment in plants, but rather that there are more which are not seen most of the time, only in the fall when plants lose their chlorophyll. That makes for some nice fall sightseeing, don't you think?

The fact that the coin toss experiment produced almost as many recessive outcomes as dominant, and that my personal planting produced and even number of recessive albinos as dominant green plants, shows that while statistics tells us we will have a particular outcome it will often take a tremendous number of tests to produce those numbers.

There are a few things that could have gone wrong with this experiment. First of all, it is possible that the corn seeds the University purchased were not all from heterozygous parents, and therefore would not be a cross between parents with both alleles. This would be a fatal flaw in the experiment, negating all of our results. It is also possible our results were thrown off by the fact that we planted some of the seeds incorrectly. If those seeds that did not grow had been planted correctly they would have added to our results and might have made a difference in our ratios. It is further possible that human error could have come into play when we performed the chromatography segment of the experiment. We might have inaccurately measured the various solutions when adding the to the mortar, or inaccurately measured the distance from the start to the various pigment levels, or just left the paper in the solution too long or to little.

The goblins all came out yellow because the allele for yellowness was dominant to the allele for blueness and the yellow goblin was homozygous (having two yellow alleles) and therefore all the offspring possessed at least one dominant allele and were yellow.

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