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Mendelian Genetics and Chlorophyll in Plants


Several common plants and animals have shared chromosomes and are identified as diploid. Mendel’s principle of segregation states that in a heterozygote, one characteristic will hide the presence of another trait for the same feature. Rather than both alleles contributing to a phenotype, the dominant allele will be conveyed entirely. In plants, chlorophyll is a dominant allele that plays a significant role in the coloration of plants and helping them make their food. However, when the plants are exposed to darkness for a significant period, the chlorophyll tends to denature, thus the plants lose their color, and the leaves change from green to yellow, whereas the stem changes from green to purple. This lab report will examine the importance of chlorophyll in plants using fast plants’ leaves and stems. The study subjects are divided into two groups where a section of them are exposed to darkness, whereas the others are placed under normal conditions. The outcome is then used to determine the importance of the chlorophyll to plants by rating them on a scale of 0% to 100%.


Gregor Mendel integrated pure breeding forms of garden peas, pisum sativum, to establish the distinct types in the crossbreeds. When to uncontaminated breeding disparities of quality were crossed, only a singular type of the trait was manifested in the F1 progeny. Mendel regarded the quality as a principal trait. The other variation that was hidden was referred to as the recessive gene. However, when F1 progeny were self-fertilized, the outcome F2 progeny always appeared in a ratio of 13, representing dominant to recessive phenotypes (Price et al., 2018). From the outcome and additional crossing, the scientist hypothesized that the aspects which define the disparity in the features segregate from each other in similar measures into gametes. Furthermore, Mendel concluded that each gamete inhibits only singular traits of the factors. These aspects are currently known as genes and distinct forms of the features were identified as alleles. Mendel’s hypothesis was approved and has since become popular as Mendel’s Law of Equal Segregation. In this lab report, we tested Mendel’s Law of Equal Segregation by crossing pure breeding strains of fast plants that varied in colors.

Materials and Method

The principal cross investigation of Mendel’s Law of Equal Segregation: 5 green leaves fast plants were acquired by eliminating all the selected green leaves from the green stemmed plants and then harvesting all the gametes that enclosed for the next eight hours. The enclosed leaves and stem were hidden from light, analyzed, and the yellow leaves and purple stems were retrieved. Furthermore, four yellow leaves were collected, examined, and placed with the green leaves in a fresh procedure while considering the standard procedure of the experiment. The cross was identified as YyAa*YyAa, where Y represented green leaves, y denoted green leaves, A for purple stem, and a for green stem. The experiment jars were incubated at room temperature with standard experimental conditions. The experiment was left for ten days after which the yellow leaves were discarded after the cross between a set of green and yellow leaves, and green and purple stem was realized. Finally, the F1 progeny was later investigated for the changes in color and structure 21 days after the cross was established.

F1 Cross for Analysis of Mendel’s Principle of Equal Segregation

A cross of the F1 leaves and stems from the above experiment was developed as follows: 5 F1 green leaves and 5 F1 stems were put in a fresh jar and closed. The experiment jar enclosed at room temperature and standard conditions. The F1 green leaves and purple stems were discarded seven days after the cross was established and the F2 gamete that was created were scored for change in color 21 days after the set-up.


To analyze Mendel’s Principle of Equal Segregation, we investigated the change in color by comparing placing green leaves and stems with a distinct color of leaves and stems, yellow and purple respectively. It was determined that the green chlorophyll is dominant in plants since it gives the plants their green color. The change from green to yellow for the leaves and green to purple for the stem denoted the dominance of chlorophyll and its roles in plants. The phenotypes of the gametes are as illustrated in the table 1 below.

Table 1: Phenotypes of the F1 Gametes

Phenotype Number of kernel
Number of kernel expected O-E (O-E)2 (O-E)2/E
Purple stem green leaves 237 9/16(455)=256 1 1 0.0039
Purple stems yellow leaves 88 3/16(455)=85 3 9 0.105
Green stem green leaves 79 3/16(455)=85 6 36 0.424
Green stem yellow leaves 31 1/16(455)28 3 9 0.321
Total 455 0.854

To further study whether there was a change in the color of leaves and stems according to Mendel’s laws, we further integrated the F1 progeny and analyzed the gametes of the resulting F2 progeny. The outcome showed the probability of the existence of four distinct phenotypes; 1=3, where in every four leaves and stems, one changed to yellow and purple respectively.

Table 2: Probability per Value

df Possibilities (per value)
0.90 0.8 0.70 0.50 0.30 0.20 0.10 0.05 0.02 0.01
1 0.0158 0.0642 0.148 0.455 1.074 1.642 2.706 3.841 5.412 6.635
2 0.211 0.446 0.713 1.386 2.408 3.219 4.605 5.991 7.824 9.210
3 0.584 1.005 1.424 2.366 3.665 4.642 6.251 7.816 9.873 11.345
4 1.064 1.649 2.195 3.357 4.875 5.989 7.779 9.488 11.668 13.277
5 1.610 2.343 3.000 4.351 6.064 7.289 9.236 11.070 13.388 15.086

From the table 2, probability= 0.85=85%, which is an insignificant variation between experimental and observes. Therefore, to support the hypothesis, the table below shows the importance of each outcome to the study subject.

Table 3: Significance of the Outcome

Probability Significance
More than 10% Insignificant
5%-10% Questionable
1%-5% Significant
Less than 1% Highly significant


The outcomes of the experiment demonstrates that chlorophyll plays a significant role in plants since its gives them their green color. The absence of the latter would mean that the plants will not be able to manufacture their own food thus resulting to the change in the stem color. On the contrary, the change in the stem color is instigated by the lack of supply of plant food and oxygen to the lower sections of the plants due to the exposure of the test subjects into the darkness (Khosravy et al., 2020). The importance of the chlorophyll is further illustrated in the ratio of plants that change color when exposed to the experiment which represented 1 plant in every four plants exposed to the test.

Additionally, calculations from the second data table shows that the probability of green leaves and stems depends on the possibility of the latter’s tolerance to the experimental conditions and the ratio which is 1:3. Despite the ratio being close to the projected ratio 3.5.1 for a green leaf and stem, the test was conducted to determine whether the experimental data varied significantly from the ration 3:5:1 ratio expected for a simple plant. The outcomes of the analysis test propose that chlorophyll is an essential part of the plants’ existence and that the statistical data do not vary from the expected 1:3 ration. Particularly, there is between 0%-10% probabilities that the variation observed are owed to the absence of chlorophyll.


In conclusion, the chlorophyll is a significant part of the plant since it necessitates the various aspects that drive the plants to existence. The phenotype F1 progeny confirmed that the gamete for chlorophyll is dominant to all plants. The ration of the yellow to green leaves and stems is identified in the F2 is significantly near that of the projected 1:3 ration for a green leaf and stem and the analysis denotes that it is within the experiment limits. Consequently, the outcome of this lab report confirms the Mendel’s principle of Equal Segregation.


Khosravy, M., Gupta, N., Patel, N., Mahela, O. P., & Varshney, G. (2020). Tracing the points in search space in plant biology genetics algorithm optimization. In Frontier Applications of Nature Inspired Computation (pp. 180–195). Springer.

Price, C. G., Knee, E. M., Miller, J. A., Shin, D., Mann, J., Crist, D. K., Grotewold, E., & Brkljacic, J. (2018). Following phenotypes: An exploration of Mendelian Genetics using Arabidopsis plants. The American Biology Teacher, 80(4), 291–300. Web.


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