To analyze:
The majority of organisms exhibit a circadian rhythm, a cycling of biological processes that are generally harmonized with day length (e.g., jet lag arises in humans when rapid movement between time zones causes established circadian rhythms to be out of synch with daylight hours). In Drosophila, pupae eclose (appear as adults after metamorphosis) at the time of dawn. Using this information,
Outline the screening method for Drosophila mutants that have an impaired circadian rhythm.
In majority of plants, such as Arabidopsis, genes whose encoded products have roles linked to photosynthesis have expression patterns that differ in a circadian manner. Using this information, outline the screening method for Arabidopsis mutants that have an impaired circadian rhythm.
Analyze the method for cloning of the genes that are identified by mutation.
Introduction:
A circadian rhythm is a natural process that is present in most living organisms. It is a biological process that regulates the wake-sleep cycle and repeats the cycle every
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Genetic Analysis: An Integrated Approach (3rd Edition)
- Following a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. What is the genotype of the F1 (progeny of Females 3 x Males 4). Select only one answer. 1. C/c D/d 2. C/C d/d 3. C/C D/D 4. c/c D/d…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Which is the genotype of the rhythmic flies resulting from the testcross? Select only one answer 1. C/C d/d 2. C/c D/d 3. C/c d/d 4. c/c…arrow_forwardFollowing a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Comparing the number of flies expected for the Parental and the Recombinant genotypes, what can be concluded about the C and D loci? Select only one answer. 1. The…arrow_forward
- Following a mutagenesis experiment to identify novel genes affecting the circadian clock in Drosophila melanogaster you discover several mutants. You start considering two of those mutants that you call c and d. The two homozygous c/c and d/d are arrhythmic (arrhythmic is the definition of their phenotype), whereas the two heterozygous C/c and D/d are rhythmic (rhythmic is the definition of their phenotype) with a 24h period. You make two true-breeding stocks: stock 3 homozygous for c and stock 4 homozygous for d. You cross them in both directions and in both cases you observe complementation with no difference between males and females. Then you take the progeny of one cross, for instance the F1 of Females 3 x Males 4, and you perform a Testcross. Out of 1000 flies resulting from the Testcross only 125 are rhythmic. Using the number of flies expected for the Parental and the Recombinant genotypes and the formula that defines recombination frequency, what is the recombination…arrow_forwardMost organisms display a circadian rhythm, a cycling of biological processes that is roughly synchronized with day length. In Drosophila, pupae eclose (emerge as adults after metamorphosis) at dawn. a)Using this knowledge how would screen for Drosophila mutants that have an impaired circadian rhythm? b)In each case, how would you clone the genes you identified by mutation?arrow_forwardSuppose a researcher has three different Drosophila strains that have mutations in the bicoid gene called bicoid-A, bicoid-B, and bicoid-C; the wild type is designated bicoid +. To study these mutations, phenotypically normal female flies that are homozygous for the given bicoid mutation were obtained, and their oocytes were analyzed using a Northern blot to determine the size and/or amount of the bicoid mRNA and in situ hybridization to determine the bicoid mRNA location within the oocyte. A wild-type strain was also analyzed as a control. In both cases, the probe was complementary to the bicoid mRNA and the results are shown below. (Anterior is on the left; posterior is on the right.) Northern blot 1 2 - 3 4 In situ hybridization Wild type Lane 1. Wild type (bicoid*) Lane 2. bicoid-A Lane 3. bicoid-B Lane 4. bicoid-C bicoid-B bicoid-A bicoid-C Which mutation is likely to cause the embryo to develop two "anterior" ends? bicoid-B Obicoid-A bicoid-Carrow_forward
- Our understanding of maternal effect genes has been greatly aided by their identification in experimental organisms such as Drosophila melanogaster and Caenorhabditis elegans. In experimental organisms with a short generation time, geneticists have successfully searched for mutant alleles that prevent the normal process of embryonic development. In many cases, the offspring die at early embryonic or larval stages. These are called maternal effect lethal alleles. How would a researcher identify a mutation that produced a recessive maternal effect lethal allele?arrow_forwardThe GAL gene system in yeast is used to metabolize galactose. In the presence of galactose, the GAL genes are expressed; however, in the absence of galactose, the GAL genes are repressed. A yeast mutant is discovered that continuously expresses the GAL genes in the presence or absence of galactose. Which one of the following mutations is likely the cause of constitutively expressed GAL genes? deletion of GAL4 deletion of the UAS elements in the regulatory regions of GAL genes O deletion of GAL3 O deletion of GAL80arrow_forwardWhat is the signaling pathway that mediates the organizing activity of the A/P organizer in the Drosophila wing disc? Describe two experiments that suggest this pathway functions to organize pattern and promote growth along the anterior/posterior axis of wing imaginal discs.arrow_forward
- Figure 13-7 illustrates the expression of the Ultrabithorax(Ubx) Hox protein in developing flight appendages.What is the relationship between where the protein isexpressed and the phenotype resulting from the loss ofits expression (shown in Figure 13-1)?arrow_forwardDiscuss how ultra violet light works as a mutagen. This could include: What is UV light and the Mutations commonly introduced by UV light? What are the Repair mechanisms in yeast that fix damage caused by UV light? Describe the phenotypes of Saccharomyces Cerevisiae plates, the first plate is the control yeast, while the second plate has been exposed to low UV light, the third plate has been exposed to high UV light. Normal yeast has round smooth white colonies. Are there any signinifcant differences?arrow_forwardTo identify genes controlling the cell cycle in budding yeast, a genetic screen was carried out. In this screen, haploid yeast cells were exposed to a DNA damaging agent to introduce random mutations in the genome. By culturing cells at an elevated temperature (e.g. 37 degrees), where many mutated genes lose their function, scientists identified yeast mutants that showed growth defects and arrest at specific stages of the cell cycle (e.g. in mitosis with large buds). In this screen, mutants of the cyclin-dependent kinase were identified, but not mutants of cyclins. Explain the reason for this outcome.arrow_forward
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