Analysis of Alcohol Dehydrogenase - Essay Example

STUDENT NAME:______________________ NUMBER:________________ MARK = /50 = / 15.0 Name of Institution: Date of Submission: 1. What is meant by the term “allozyme”, give two examples (apart from ADH and α-GPDH) and explain why allozymes are useful to population geneticists. The term allozyme refers to allelic enzyme variations that result due to the encoding of the structural genes. Enzymes are proteins in nature and are made up of Amino Acids, in which some of them have electrical excitement or charge. Allozymes are useful to the study and analysis of the population genetics because of their simplicity. During electrophoresis, allozymes do not need DNA extraction and even their analysis does not require the sequence information availability, probes or the primes, they are easy to use and act quickly. 2. Describe how the process of protein electrophoresis is used to separate and score allozymes. The application of electrophoresis is established on the principle that DNA has a net negative charge at a pH which is neutral because it has a phosphate backbone. And as a result of this, when a DNA is subjected to a electrical potential, it migrates to the positive pole. The migration rate towards, a positive pole is controlled or slowed down by making the DNA move through an agarose gel which acts like a buffer solution. The permeable lattices are created in the buffer solution forcing the DNA to pass through the pores in the lattice while migrating to the positive pole. Large DNA molecules are relatively slowed than their smaller counterparts. This application will therefore separate a mixture of small and large DNA fragments depending on their sizes. Interpretation: The molecular size of a DNA fragment which is unknown can be approximated through the comparison of distance covered and the molecular weight standard. 3. Are there any shortcomings to using allozymes in population genetics? A major weakness or shortcoming of using allozymes in population genetics is because of their comparative low degrees of polymorphism and their low abundance. Besides, proteins that have similar electrophoric movement (co-migration) are hardly homologous in germplasm that are distantly related. And this raises the question in the nature of their selective neutrality.(Ross and Krieger, 2002). Finally many at times, allozymes are taken to be molecular markers because of their enzyme variant representation and that enzymes are also molecules in nature. Moreover, even though allozymes are phenotypic markers, they are no exception to the effects of the environmental conditions. An illustration could be, the banding profile established for specific allozyme marker is subjected to alterations or change following the tissue applied for the analysis. This due to the fact that one gene has the capability of being expressed in one tissue only. 4. What is the physiological role of alcohol dehydrogenase (ADH) in D. melanogaster? ADH is a protein with multifunction and its responsible for the systematic and sequential diminishing or reduction of acetyl-COA to acetaldehyde and eventually to ethanol within the conditions which are fermentative. Also the ADH- genotypes very in the optimum of the propan-2- ol into aceton oxidation rates in vivo. They play a key role in the elimination ethanol in the forms of ADH-7 Ik >ADH-F>ADH-S. This generates allozymic efficiency in D. Melanogaster 7. Was there any evidence for selection for the fast or slow allozymes of α-glycerophosphate dehydrogenase (α-GPDH) in the D. melanogaster populations? Explain using the calculations from the lab exercise. ( A chi-square goodness of fit critical value can be calculated by the formula: 2 =  (O-E)2 E Degrees of freedom can be calculated by: d.f. = n-1 (or as above for tables) TABLE 1. Critical values of the chi-square distribution. CLASS DATA TABLES (i) Genotypic data (the number of individuals in per genotypic class) ADH αGPDH Environment Genotype ♂ ♀ ♂ ♀ Lab (L) FF 4 6 5 2 FS 4 3 2 6 SS 2 1 3 2 Total 10 10 10 10 Bush (B) FF 2 3 4 2 FS 3 2 4 4 SS 5 5 2 4 Total 10 10 10 10 (ii) ADH and αGPDH linkage (note: irrespective of environment and sex) Genotypes αGPDH-FF αGPDH-FS αGPDH-SS Total ADH-FF 5 3 7 15 ADH-FS 3 2 7 12 ADH-SS 5 5 3 13 Total 13 10 17 40 analysis: 6. Was there any evidence for selection for the fast or slow allozymes of alcohol dehydrogenase (ADH) in the D. melanogaster populations? Explain using the calculations from the lab exercise. In the determination of the incidence of the slow and fast alleles amongst all of the alleles sampled at each site (2 x 20 for each of the two allozymes, at each site). Applying the data above, the frequency of the ADHF allele in the lab is two times the number of ADHF homozygotes (both males and female) plus the number of heterozygotes (both males and female) all divided by the total number of alleles ie. = ((2 x 10) + 7)/40 = 0.675. N=20 Frequency= 0.675 The frequency of the ADHS allele in the lab population can be calculated in the same way. Complete the table below using the obtained data or that from over the page. P q Lab Bush Lab Bush ADHF 0.333 0.357 αGPDHF 0.310 0.431 ADHS 0.352 0.481 αGPDHS 0.365 0.453 8. Are the genes for alcohol dehydrogenase (ADH) and α-glycerophosphate dehydrogenase (α-GPDH) linked in D. melanogaster? Explain using the calculations from the lab exercise. Genotype frequency: Calculations: The lab frequency of ADH-ff genotype =(P)2 = 0.675 x 0.675= 0.456 The expected Number of Lab ADHff= =(20x 0.456)= 9.12 The chi-square checks the similarity of the data predicted and the data obtained from the experiment, Hence= Table (ii) expected number of ADH-FF/αGPDH-FF = (13 x 15)/40 = 4.9 ) Using the chi-square test of independence to evaluate linkage between the two loci shows that ; None of the two pedigree ADH populations is in Hardy-Weinberg equilibrium as was suggested by the results of the Chi-square test. This indicates the possibility of other processes impacting on this population to make the allele frequencies to vary or show a significant deviation from the Hard-Weinberg equilibrium. This could have resulted due to the non-random breeding of this specie or because a relatively smaller sample was used in the analysis could have also brought some effect. • References: 1. C.S. Mellersh., Zajc, I, and M. Sampson. 1998. Variability of canine microsatellites within different dog breeds. Mammalian Genome 8: 188-197. 2. Lab Manual Read More