Drosophila Cross I: Segregation/Independent Assortment
Objective:
The purpose of this experiment was to understand how traits are passes from generation to generation, from parent to offspring. We learned how identify male and female Drosophila flies along with traits dealing with wing shape and eye color. Also, we explored and reaffirmed Mendel's Laws of Independent assortment and Segregation by growing fruit flies and following traits throughout the flies lineage.
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Results:
One tube for the initial F1 cross utilized dumpy females and sepia males. A second tube contained the reciprocal cross. All females used were checked to make sure they were virgins. With a missed week in lab we were unable to remove the parents in the flies. The following weeks to obtain the data for the crosses shown in the tables below, we used flies prepared by the previous weeks Friday
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The parental crosses should have been virgin females with genotype dp-se+ and phenotype dumpy wings and wild type, red eyes with sepia males with the genotype dp+se- and phenotype normal wings and sepia eyes, along with its reciprocal cross. Due to lack of flies during lab, we only made tubes for virgin dumpy winged female and sepia male. The following week we were unable to remove the parent flies, so we had to use a previous labs premade flies to continue the experiment. An important concept to understand, that was not tested in this experiment, was that reciprocal crosses cannot be treated as the same for Drosophila when the traits observed are sex-linked. In this case the traits we are observing are not sex-linked, so it does not matter with our test cross. It was also important to use only virgin females when conducting all crosses to ensure that the female has not stored any semen for use later in mating. Thi was necessary so that we saw proper distribution of traits according to parental phenotype and genotype
Variation in selection pressures on the goldenrod gall fly and the competitive interactions of its natural enemies
The objective of this experiment is to determine what genes are responsible for the white-eye color in two strains of Drosophila melanogaster, known as the common fruit fly. Drosophila is used as the experimental organism for many reasons which include its small size, easy maintenance, short 10 day generation time, and a fully sequenced genome. The characteristics of the wild type, which is the most common phenotype found in nature, include brick red eyes, long wings, gray/tan body, and smooth bristles. Of course, there are mutations that occur that cause specific traits to deviate from the wild-type phenotype. These traits include wing length, bristle shape, body color, and eye color.
17. Fruit flies normally have eight chromosomes. The diagram below shows the result of meiosis in three fruit flies to produce gametes with the number of chromosomes indicated. The male then mates with both female A and female B to produce three zygotes (1, 2, and 3).
Genes are expected to give offspring hereditary similarities to the parent. However, this was not known and Gregory Mendel asked himself what was passed on by parents to their offspring that is the basis for similarity. Mendel would go on through experiments with pea plants to answer short questions. The answers were short as well as to say that the passing of characteristics from parents to the offspring is throug...
The F2 punnett square shows that there should not be a female fly that has apterous wing mutation. Our observed experiment showed that female flies are capable of forming in the F2 Generation. Therefore, the mutation is located on autosomal chromosomes. In trial 1, the p value is not significant. This could be due to the fact that the male to female ratio in the F1 generation was unequal. In trial 2, the p value is significant and likely due to chance. The probability error is between 1 % and 5%.
An individual can be homozygous dominant (two dominant alleles, AA), homozygous recessive (two recessive alleles, aa), or heterozygous (one dominant and one recessive allele, Aa). There were two particular crosses that took place in this experiment. The first cross-performed was Ebony Bodies versus Vestigle Wings, where Long wings are dominant over short wings and normal bodies are dominant over black bodies. The other cross that was performed was White versus Wild where red eyes in fruit flies are dominant over white eyes. The purpose of the first experiment, Ebony vs. Vestigle was to see how many of the offspring had normal bodies and normal wings, normal bodies and vestigle wings, ebony bodies and normal wings, and ebony body and vestigle wings.
Nettie studied Tenebrio molitor beetles and found that unfertilized eggs in female beetles always contain an X chromosome. Sperm from male beetles contain either an X chromosome or a Y chromosome. She found that eggs fertilized by sperm carrying the X chromosome produce female beetles. The combination of egg and Y-chromosome sperm produce male beetles.
Charles Darwin’s theory of natural selection explains the general laws by which any given species transforms into other varieties and species. Darwin extends the application of his theory to the entire hierarchy of classification and states that all forms of life have descended from one incredibly remote ancestor. The process of natural selection entails the divergence of character of specific varieties and the subsequent classification of once-related living forms as distinct entities on one or many levels of classification. The process occurs as a species varies slightly over the course of numerous generations. Through inheritance, natural selection preserves each variation that proves advantageous to that species in its present circumstances of living, which include its interaction with closely related species in the “struggle for existence” (Darwin 62).
Some individuals have developed different traits to help them in the process of intra-sexual competition. The organisms with more distinctive traits have greater reproductive success. More genes of those traits are then ‘selected’ and are passed onto the offspring of the organisms. Throughout time variability in these traits becomes
... of Genic Heterozygosity in Natural Populations. II. Amount of Variation and Degree of Heterozygosity in Natural Ppopulations of Drosophila pseudoobscura. Genetics 54:595-609.
In Drosophila (fruit flies) genes can be linked or non-linked. Linked genes are genes that are close together on the chromosome so they often appear in pairs. Non-linked genes are not close together and Mendel’s law of Independent Assortment states that each trait is equally likely to slow up. The purpose of this lab is to find out if the genes of purple eyes and black bodies are linked in Drosophila. Flies are good for this experiment because they display a number of different traits and they mate quickly. If the eye and body color genes are linked in Drosophila then the F2 generation will not have a 9:3:3:1 ratio because the genes are on the same chromosome and cannot independently assort when they are crossing over. Since linked genes often appear in pairs, it is likely that there will be many more flies that are wild-type for both genes or have purple eyes and a black body than a combination of these genes. If the eye and body color genes are not linked in Drosophila then the F2 generation would have a 9:3:3:1 ratio because the law of independent assortment states that each gene has an equal chance of occuring.
This lab report dealt with the analyzation and transmission of genetic traits in monohybrid and dihybrid crosses using Caenorhabditis. Mutations will be either dominant or recessive or X-linked or autosomal. Where using a sterile pick you will pick certain worms and place them in a new petri dish for them to reproduce and observe new progenies, mutations and different crosses.
In addition variable recombination frequencies at different environmental conditions can ensure genetic variation as well. When observing the results from different crosses it can be observe how temperature influences the behavior of the organisms. The results are due to the effects of temperature upon crossing-over and that chiasma interference in conjunction with differences in chromosome structure may account for the three varied patterns of segregation. (Olive 1956).This paper discusses and investigates, whether there was natural genetic variation for recombination frequencies and whether any such variation was environment related and possibly adaptive (Salem2001).
Past research has shown increases in the recombination rates due to environmental stressors including age, food availability, behavioral stresses, chemicals and most importantly temperature. This study looks at the effects of an increase in incubation temperature on recombination rates in Drosophila melanogaster. A wildtype parent for three genes (al+ dp+ and b+) was crossed with a recessive parent (al dp b). These genes included presence of aristala, wing type and body color, all found on the second chromosome. The parents were mated and the organisms were divided into two different vials each placed in a different temperature; one in 25°C and the other in 30°C. The offspring were counted based on their phenotype for the three studied traits. It was predicted that there would be an increase
Complete dominance also means that a dominant allele can mask or cancel out the effect of a recessive allele if an offspring if they inherited different alleles from their parents. Inheriting a dominant allele from one parent and a recessive allele from another parent for a trait is the definition of an individual being heterozygous for a trait. While the organism in question does not show the recessive allele physically, it can be passed down to offspring and possibly be shown if the other parent also passes down a recessive allele. In order to know whether or not offspring are heterozygous for a trait, test crossing two offspring from the same parents can help determine a genotype. If it is found that an offspring has two dominant alleles for a trait, they are homozygous dominant for that