Essay About Summary Of The Experiment And Formal Laboratory Report

Plant Genetics
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This document is not meant to be a substitute for a formal laboratory report. The Lab Report
Assistant is simply a summary of the experiments questions, diagrams if needed, and data tables
that should be addressed in a formal lab report. The intent is to facilitate students writing of lab
reports by providing this information in an editable file which can be sent to an instructor.
Many modern theories of heredity find their origins in experiments, originally conducted by Gregor
Mendel, on the crossbreeding or hybridization of garden peas. See Figure 1. Like humans, these
are diploid organisms, containing pairs of alleles or genes for each trait, located on chromosomes.
Characteristics that are inherited are called traits, and Mendel was the first person to accurately
predict how and in what relative frequency traits would be transferred from one generation to
another.
Mendel started his research in genetics by using true breeding plants in which each generation
that self-pollinated looked exactly like the previous generation. It is easier to study genetics when
only one characteristic would change, such as purple versus white flowers. When plants are
crossbred and differ in only one trait, this is called a monohybrid cross. Tobacco seeds used in
this experiment are also monohybrids because only trait will be studied and that is color.
In the parent or true breeding generation of the tobacco seeds, both alleles are the same in each
plant–either both green or both albinos. In the first generation of the cross or F1 generation, all
seeds contain two different alleles: one green and one albino. Since the green allele is dominant,
the seeds will all appear green. In the next generation of cross, the F2 generation, there are four
possible combinations of alleles. Thus, because it is possible for some seeds to contain two recessive
alleles for albino, it is possible for these recessive alleles or genes to determine the phenotype or
appearance of the seed. Through his experiments, Mendel stated the rule of dominance that says
certain alleles are dominant and others are recessive. When both the dominant and the recessive
alleles