F 1 Generation Data Phenotype Females Males example essay topic

Lab report Students perform genetic crosses with living organisms to analyze F 1 and F 2 generations. The use of monohybrid, dihybrid, and sex-linked crosses gives students a variety of experiences in interpreting data. The purpose of this lab is to use genetic crosses to illustrate independent assortment and sex-linkage in the fruit fly, Drosophila melanogaster. You will be given monohybrid, dihybrid, and / or sex-linked crosses with well-defined mutant traits. Over the course of four weeks, you will observe and record what happens to the mutant traits as they are passed from one generation to the next. Additionally, you will learn the life cycle of the fruit fly and learn how to recognize the sex of fruit flies, and several types of classic mutations.

Lastly, you will compare the predicted results with the actual results using a chi-square analysis This will ensure that only the desired males will contribute to the offspring in the cross. A female can store enough sperm from a single mating to fertilize all the eggs she produces in a life time. X linked recessive (white) DISCUSSION The results from the monohybrid cross for both my class and for all sections were very close to the expected results. "Theoretically, there should be three red-eyed flies for every one sepia-eyed fly. We call this a 3: 1 phenotypic ratio" (So What's a Monohybrid Cross Anyway? 2).

As indicated in table one, the data comes within one or two tenths of the 3: 1 ratio. Therefore, the monohybrid cross was very accurate. However, the results from the dihybrid cross were not quite as accurate. Mendel hypothesized and proved that a dihybrid cross should produce a 9: 3: 3: 1 ratio (Biology 245). In our experiment, the results from my class (both sexes) were not very close to the ratio. In table 2, the ratio shows 6.6: 2.9: 2.8: 1.

The data obtained from all classes were slightly more precise. All sections together (both sexes) produced a ratio of 9: 2.9: 3.5: 1. There are many reasons that our results did not match the expected ratios. For example, when transferring flies from one vial to another, a few flies got away which could have a small effect on the numbers. Another factor affecting the results also happened upon transferring flies. A number of flies were imbedded in the cultural medium.

We were forced to leave them there so that we didn't loosen the medium. The largest source of error in the "my class" column came from the amount of time we allowed the flies to reproduce. Since Easter vacation occurred during our lab period, our second generation flies were permitted to stay together for two weeks instead of one. This may have resulted in the F 2 generation flies mating with their own offspring, thus throwing off the ratio.

I feel more certain about the results in the "all classes" column since many more trials were performed and more flies were used. In any experiment, the more trials one conducts, the more accurate the results will be. This makes sense when comparing the results from my class versus the results from all classes combined. The numbers of flies used in each column make the difference in trials more evident: 1,060 flies were produced in my class, whereas 26,623 flies were produced in all classes. In the monohybrid cross, the ratio for eye color for the females were consistent with the ratio for males. This information implies that the gene for eye color is not sex linked.

Through research, I found that in Drosophila melanogaster, chromosome one is the sex chromosome. Eye color is not one chromosome one, but rather on chromosome three. Therefore, eye color in Drosophila is not sex linked (Genetics: Drosophila Crosses). In each column, the number of females produced outweighed the number of males.

This may imply that the X chromosome is dominant over the Y chromosome. This would cause the X chromosome to mix with another X chromosome, producing a female, more often than it would mix with the Y chromosome, which would produce a male. As a follow-up to the experiment, I would perform many more trials than each person did for this experiment. Also, more flies could be placed in each vial to ensure even more offspring to be included in the data. I would also be sure to remove the flies after just one week to reduce breeding between generations. This experiment caused Mendel's findings to be more concrete and realistic in my mind.

It made the information more than meaningless numbers. The experiment also made me realize how easily biological ideas can be proved. Our results agree with Mendel's discoveries. The only drawback to our learning was the massacre of over 26,000 fruit flies. Table 1: P Generation Data Phenotype Females Males red eye 4 3 white eye 0 0 Table 2: F 1 Generation Data Phenotype Females Males red eye 28 14 white eye 0 15 Analysis of Results 1.

Describe and name the observed mutation (s). The only distinguishing characteristic was the white eye colour found in the F 1 generation. 2. Write a hypothesis which describes the mode of inheritance of the trait (s) you studied.

This is your null hypothesis (as described in the statistical analysis section). White eye colour is a sex linked trait. The white eye colour gene is located on the x-sex chromosome. 3. The expected ratios for the genotypes and phenotypes of the F 1 generation was recorded in the table below. Expected Genotypic Ratio Expected Phenotypic Ratio F 1 1/4 XRXR: 1/4 XRXr: 1/4 XRY: 1/4 XrY or 1: 1: 1: 1 1/2 red eye female: 1/4 red eye male: 1/4 white eye female or 2: 1: 1 4.

The actual ratios for the genotypes and phenotypes of the F 1 generation are recorded in the table below. Actual Genotypic Ratio Actual Phenotypic Ratio F 1 14: 14: 14: 15 28: 14: 15.