Robert Warren, Lisa Nagy, Jane Selegue, Julie Gates, and Sean Carroll produced this experiment that wanted to examine homeotic gene expression in butterflies. The hypothesis they tested was do homeotic genes have driven morphological change or do the homeotic genes provide a pre-existing plan where insects segment diversity evolved. The genes Antp, Scr, Abd-A, and Ubx were isolated from a cDNA library and were used to explore differences in limb and wing numbers between flies and butterflies. Where Ubx and Abd-A are expressed, the limb and wing numbers arose. They started to wonder if the expression of BX-C genes were different in butterflies (P.Coeni) and fruit flies (drosophila). When they did tests, they saw that conservation of BX-C and ANT-C homeotic gene expression are fundamentally similar and don’t explain the differences in appendages in each species. They looked into embryogenesis, and at 20% of the embryogenesis of butterflies, they saw Abd-A protein and RNA are expressed in the anterior and abdominal segments. High levels of Antp expression are seen in the thorax. Past the 20% mark of embryogenesis, the patterns seen of Abd-A, DII, and Antp expression differed extremely - no DII or Antp were expressed in the abdominal proleg.
After seeing this, they tested out if DII is responsible for the down regulation of Ubx/Abd-A. They used double-label experiments using antibodies against butterfly DII and Ubx/Abd-A antibodies and performed them. The activation of DII in the proleg trails repression for Ubx and Abd-A expression, which showed that repression of BX-C gene, is the initial event. When DII expression abdominal segments of drosophila embryo expression is repressed due Ubx and Abd-A, the abdominal limb formation in but...
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...nes to produce different kinds of structures patterned in the same position. In general, 0 changes the number, size, pattern of homologous structure, and body appendages, that involve changes in timing and spatial regulation of existing genes. In some cases, these are homeotic genes and in other cases they are downstream genes.
If I were to continue this line of research, I would test and see if there are different hox genes for different animals. I would expect to see duplication to occur in the lineages within each species. For example, if duplication were to occur at hox gene levels (in butterflies, fruit flies, earthworms, etcetera) I would expect to see different hox genes. But, since hox how genes are conserved, that would probably not end up happening. So this new test would prove that hox genes are conserved and every species should have the same hox genes.
There is no doubt that arthropods are an extremely successful group of animals, with an estimated 5-10 million species worldwide[1], and this can be attributed to having an exoskeleton; it provides many benefits, such as protection from parasitism and other threats. However, one major disadvantage of having an exoskeleton is the limitations that an inelastic cuticle can place on growth. The exoskeleton provides protection, but when freshly moulted the animal is soft and vulnerable, as well as having limited mobility and use of appendages; many seek shelter before moulting[2]. There are similarities and differences between the moult cycles of all the arthropods, however only crustaceans and insects will be discussed here.
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.
Eyesenkes theory provides an amicable solution. If we could assume that this information was genetically coded in to the cells at birth then this no longer becomes an issue and we can explain how’s and why the constructs are laid down to a loose genetic template i.
Long standing arguments against the theory of natural selection stem from the occurrence of incipient structures and complex traits in organisms despite the seemingly stochastic nature of mutations. Many complex adaptations observed in nature today are thought to have arisen from less complex ones with simpler functions, therefore these characters are thought to have been “pre-adapted.” In order to go from a simple to a complex structures there must have been a transitional phase, where the two structures function simultaneously or where the new function is assumed without interfering with the old function. These structures are termed incipient or incomplete, and given what we know to be true of natural selection and the theory of evolution it becomes hard to reconcile the idea that natural selection continued to favor these structures despite the lack of selective value. Incipient structures are thought to be neither sufficiently large enough not elaborate enough to perform an adaptive function and thus it also becomes difficult to understand how larger complex characters arise. A discussion of morphological and developmental genetics explains that these structures have been performing useful functions since their simple origins, therefore being selectively favored while at the same time evolving to become large enough to accumulate new more complex functions. Modification of pre-existing genes and regulatory circuits in early development has been extensively studied in metazoans, Hox genes and the development of complex structures such as eyes, limbs and appendages. Phenotypic variation is therefore generated via the modification of existing genes, regulatory processes and developmental processes and this variation is acted o...
Drosophila is a small fruit fly, it is about 3mm long. This insect is a model organism most commonly used in developmental biology and genetics. The Drosophila fruit flies are especially suited in experiments because of their short life cycle which consist of two weeks; they easily reproduce many offspring, and are also cheap1. The drosophila contains four chromosomes that can easily be experimented on, which allows in-depth observation. In this experiment, Drosophila melanogaster were used to identify the properties of Mendelian inheritance. The Law of Segregation states that allele pairs separate during gamete formation and randomly unite during fertilization and is carried by every individual. The Law of Independent Assortment states that each parent randomly passes on alleles to their offspring. Although, the Law of Independent assortment does not take in account the patters of sex-linked inheritance.
Several models have been proposed to explain why might Archaeopteryx or its decedents develop the ability to fly. The “pouncing proavis” or “trees-down” model was proposed by J.P. Garner and colleagues in 1999. They theorize that birds evolved to the ability to fly by first living in trees and then gliding down to ambush prey. Natural selection favoured individuals that could glide the furthest to catch prey and eventually led to the origin of flight. Garner and colleagues (1999) believed that this theory explained three aspects of early flight: the model matches observed secession in flight evolution based on fossil records, it predicts a primitive bird-like animal had few adaptions to flapping but very complex aerodynamic feathers, and it explains the origin of rachis in feathers.
McCall, Robert A., Sean Nee and Paul H. Harvey. "The role of wing length in the evolution." Evolutionary Ecology (1998): 569-580. Web.
Referring to the manipulability account, if scientists would change the heritable differences in physical characteristics of the organism in a population, there would be a visible change in their reproductive success (Millstein, 2006). For example, in a population of beetles with varying abilities to withstand different temperatures, a new beetle genotype is introduced that can withstand a greater range of temperatures, and we would expect that the relative reproductive success of the other genotypes would decrease (Millstein, 2006). Phylogenetic relationships among the four Radix species are inferred based on their genomes and nuclear loci (Feldmeyer, 2015). Three different tests to infer selection and changes in amino acid properties yielded a total of 134 genes with signatures of positive selection (Feldmeyer, 2015). The majority of these genes belong to functional genes including reproduction, genitalia, development, and growth rate (Feldmeyer, 2015).
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.
The majority of scientific work in genetics and genomic sequencing has been done in the last 155 years. In 1859, Charles Darwin published On the Origin of Species where he proposed evolution by natural selection. Evolution is the change of inherited characteristics of biological populations over successive generations.Yet, the principals of genetics required to explain how characters are ...
sequence. Epigenetics in turn affects how cells read the genes. Epigenetic change is a regular and
Davis, Lloyd S. and John T Darby. Penguin Biology. San Diego: Academic Press, Inc., 1990.
A lot of butterflies have developed eye spots on their wings. These eye spots provide the butterfly the facade of a much bi...
Jeffery Turner and his team of bio-scientists at Nexia Biotechnologies; alongside Randolph Lewis, Ming Xu and Michael Hinman from the University of Wyoming; have taken the genes responsible for a spider’s silk produc...
J. Losos, K. Mason, S. Singer, based on the work of P. Raven, & G. Johnson, Biology, 8th ed., (McGraw-Hill Education (Asia), Singapore, 2008), pp. 994-995.