Genetic Crosses in the Fruit Fly Drosophila melanogaster
Introduction
Since the turn of the 20th century, Drosophila melanogaster, the common fruit fly, has been a useful organism for the study of genetics. Its relatively short generation time (approximately 10 days at 25oC) yields a large amount of breeding data in a short period of time. Because of its simple food requirements and easy handling in the laboratory, large and varied stocks of Drosophila can be maintained with minimal cost and effort (Ashburner, 2008).
The general anatomical features of a male and female wild type fruit fly and the organism’s life cycle are shown in Figure 1. Recognizing various structures of the adult organism, especially sexual differences, will be important
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The entire developmental cycle takes about 14 days at 21oC (close to lab room temp). At higher or lower temperatures, the cycle is proportionally shorter or longer. Eggs are tiny, oval, white objects about 1 mm long with two long filaments at one end. Larvae hatch from the eggs about a day after they are laid. Larvae are white, segmented, worm-like burrowers with black mouthparts at their anterior ends and a pair of spiracles (short tubes) for tracheal breathing at both their anterior and posterior ends. Larvae vary from about 1-7 mm in length when ready to pupate. Since their cuticles (skin) will not stretch, the larvae periodically molt to reach adult larval size. There are two such molts during Drosophila development. Before and after molts, larvae are called instars; thus, the fruit fly has three instars. After the second molt, the third larval instars crawl from the medium onto the sides of the culture vessel and …show more content…
1. The last abdominal segment of the male is much larger and more rounded than that in the female.
2. The abdomen of the male contains only five segments while that of the female contains seven.
3. The male's body size is generally somewhat smaller than that of the female.
4. The male has a small, densely packed tuft of bristles known as a sex comb located on one of the outer joints of both forelegs. (The female lacks these).
Variation in selection pressures on the goldenrod gall fly and the competitive interactions of its natural enemies
In science, these fruit flies can be used to study genes and mutations relatively quickly because of the limited life span. Knowing mating behaviors can help scientists better understand their results and improve their experiment designs to reduce
Examining the Crosses Between Drosophila Fruit Flies Introduction The major topic of this experiment was to examine two different crosses between Drosophila fruit flies and to determine how many flies of each phenotype were produced. Phenotype refers to an individual’s appearance, where as genotype refers to an individual’s genes. The basic law of genetics that was examined in this lab was formulated by a man often times called the “father of genetics,” Gregor Mendel. He determined that individuals have two alternate forms of a gene, referred to as two alleles.
They found that their groupings of similar shaped pelvic girdles fell into the correct category, except at the family level.
Sex is the biological composition of either a male or female. For example, females have XX chromosomes in their DNA; their reproduction system consists of an egg and a vagina, and they also have functional breasts. Males, on the other hand, have XY chromosomes in their DNA; their reproductive system consists of sperm, testes, and a penis. Gender is the array of characteristics that distinguish a male from female and according to their attributes. However, there are some people whose sexual organs are imperfect, according to the roles of gender and sex, an example are hermaphrodites, because they have both a male and female’s sexual organs. Hermaphrodites tend to stay in the middle, grayish area between a male and a female. Society uses binaries to classify a male as men, with masculine traits, and a female as women who have feminine traits. Masculine traits are the roughness, muscles, broad shoulders, and deep voice men, or women, can possess. On the other hand, feminine traits include the long hair, soft skin, angelic glow and soft voice that either a women or men can own.
Evidence for this conclusion could be found in all four of the bones. The pelvis had a sub-pubic angle of 100 degrees and a greater sciatic notch with 76 degree angle. Both of these measurements are greater than the minimum angle requirements for it belonging to a female (90 degrees and 68 degrees respectively). It also had a pelvic cavity shape that was noticeably circular and wide as opposed to the heart shaped male pelvis. The skull also had several feminine features including the sharp eye orbit edge, round eye orbit shape, smooth nuchal crest, round and globular frontal bone, and rounded v-shaped mandible. Evidence can also be found in the femur’s length (385mm.) which is under the 405mm. female requirement. Evidence can also be found in the various humerus measurements such as it’s 54.2mm. epicondylar width and it’s 37.5mm. vertical diameter of the numeral head, both of which were significantly closer to the female average than the male average. Out of the nineteen sex determination tests, only two matched male criteria. Ultimately this abundance of affirmative evidence prove that the bones were, in fact,
However, many of our questions still remain. The purpose of this paper is to discuss the physical aspect of gender differences in humans, otherwise known as sexual dimorphism, it’s evolutionary history in our species, and some behavioral and societal trends that are associated with it. To accomplish this, I will begin by outlining the anatomical structures that are commonly used in measuring sexual dimorphism in our species. After establishing these criteria, I will expand upon the evolutionary history of sexual dimorphism in humans beginning with the anthropoids in the Oligocene and ending with present day trends.
In order to figure out the genes responsible, there are several other factors that must be determined. These factors include the number of genes involved, if each gene is x-linked or autosomal, if the mutant or wild-type allele for each is dominant, and if genes are linked or on different chromosomes. Proposed crosses include reciprocal crosses between the pure-breeding mutants of strains A and B with the wild-type will help determine if the genes or sex-linked or autosomal, in addition to which alleles are dominant (8). Another proposed cross includes complementation crosses between pure-breading mutants from strains A and B to determine if one or two genes are involved (8). Furthermore, testcrosses between F1 progeny and pure-breeding recessive mutants from strains A and B, which will help determine if genes are linked on the chromosome or if they assort independently (8). These proposed crosses are shown in the attached
There are nearly one million species of insects known. Insects are defined by having six legs and a body divided into three segments: head, thorax, and abdomen. Chitin is an organic material that makes up an insects exoskeleton. There are three life cycles of insects, ametabolous or incomplete and paurometabolous or gradual, and homotabolous or complete metamorphosis. These life cycles are important in the aging of insects for aiding in legal investigations, (Houck and Siegel. Entomology).
They are very popular because they have a relatively short life cycle, which lasts about 9 days. This makes it easy to observe multiple generations in a short period of time. The fly’s life cycle consists of egg, larvae, pupa, and adult stages. At each of these stages of development, Drosophila exhibits different phonotypical identities and mutations. The flies that were crossed contained a genetic mutation called apterous. Apterous can be observed by looking for flied that are missing wings. Flies with apterous will not have any wings. If this mutation is sex linked, it is expected that the male population will only be wingless in the F2 generation. If the mutational is autosomal, it is expected that the mutation to normal fly ratio is
Transferring sperm depends on the species of damselfly because the sex organs are particularly elaborate and specific to the each species. Organs in the male damselflies that allow the end of its’ abdomen to attach to the back of the females’ head correspond between each individual species, making mating between separate species nearly impossible.
The idea of the project was to experiment breeding Drosophila Melanogaster (fruit fly) to figure out if certain genes of that species were sex linked or not (autosomal). A mono-hybrid cross and di-hybrid cross was performed. For the mono-hybrid cross, white eyed female and red eyed male were placed in one vial for them to reproduce. For the di-hybrid cross, red eyed and normal winged flies and sepia eyed and vestigial winged flies were placed in their vial to reproduce. In the mono-hybrid cross the results expected were within a 1:1:1:1 ratio. Expected results similar to the expected desired null hypothesis proposed with what the F1 parental generation breeds. The potential results would have had to have been within the ratios of 9:3:3:1. The results were clear and allowed the null hypothesis to be correct. The white eyed gene in the fruit flies is sex linked. Sepia eyes and vestigial wings are not sex linked and are examples of independent assortment.
When looking at the biological make up of male and females, there are both similar physical characteristics
Most of today’s theorists and scientists have a different perception of determining whether or not gender can be based on biological factors, or evolutionary factors. Gender determination involving humans can be identified by evaluating male and female chromosomes. Theorist of Penn State (2005) contains that chromosomes is a combination of instructions used to produce organism. As previously stated, the male chromosomes consist of X and Y. These two chromosomes are responsible for creating male gender and their ability to produce sperm. The female egg consists of double XX chromosome. Based on this theory, the X chromosomes carry a more dominant instruction manual than the Y chromosome.
A baby is born and the doctor looks at the proud parents and says three simple words: “It’s a boy”, or “It’s a girl!” Before a newborn child can even take his or her first breath of life, he or she is distinguished and characterized by its gender. One important factor to know is the difference between gender and sex. Sex...