Concept explainers
Honeybees (Apis mellifera) provide a striking example of environmental effects on eukaryotic gene expression and thus
It turns out that the diet of the larval (larvae are young developing insects) females controls their development as either workers or queens. When the hive needs new queens, a few female larvae are fed royal jelly, a substance secreted by worker bees, instead of the normal diet of nectar and pollen. Investigators determined that many genes are more highly CpG-methylated in the larval-stage workers than in the larval-stage queens
a. | Describe an experiment you could do to determine if DNA methylation correlates with differences in gene expression in workers and queens. |
b. | Researchers were able to mimic the effect of royal jelly by knocking down the expression in female larvae of a DNA methyltransferase enzyme called DNMT3. (The knockdown was accomplished through a technique called RNA interference that is described in a later problem; the details are unimportant here.) Remarkably, when fed a normal diet, most of these larvae developed as queens. Based on the description of the transgenerational silencing of the
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ND STONY BROOK UNIVERSITY LOOSELEAF GENETICS: FROM GENES TO GENOMES
- Discuss the morphological differences between the parasegments and segments of Drosophila. Discuss the evidence, providing specific examples, that suggests the parasegments of the embryo are the subdivisions for the organization of gene expression.arrow_forwardOur 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_forwardIn times of nutrient stress, the cellular slime mold Dictyostelium discoideum develops one of two cell types: pre-stalk and pre-spore. Scientists studying this development discovered that the pH of individual cells regulates the type of cell that is formed. Which of the following claims could scientists make about how environmental cues affect the gene expression of Dictyostelium discoideum? A - A response to nutrient deprivation leads to a change in pH that causes mutation in the cells, forming the different cell types. B - A response to nutrient deprivation leads to a change in pH that disrupts the cells, forcing them to develop into certain cell types. C - A response to environmental stress leads to a change in pH that triggers transcription factors to differentiate the cell type that will be formed. D - A response to environmental stress leads to a change in pH and a decrease in transcription factors that differentiate the cell type that will be formed.arrow_forward
- Suppose 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_forwardResearchers have exploited Minute mutations in orderto study the phenotypes associated with recessive lethal mutations (l−) that decrease the rate of cell divisionand thus make only very tiny homozygous mutant clones that are difficult to analyze. Many differentstrains of Drosophila carry dominant loss-of-functionMinute (M) mutations in a variety of genes encodingribosomal protein subunits. The M genes are haploinsufficient; flies with only one wild-type M+ gene copyhave a slower pace of cell division, and thus prolongeddevelopment and subtle morphological abnormalities.To circumvent the tiny clone problem, researchersgenerate GFP-marked homozygous l−/ l− clones thatare also M+/ M+, in flies that are l−/ l+ and M−/ M+.The loss of the Minute mutation only in cells withinthe clone gives the l−/ l− cells a growth advantageover their neighbors, enabling the mutant clone togrow large enough to study. Diagram chromosomesthat could be used to generate such clonesarrow_forwardThe floral homeotic genes of Arabidopsis belong to the MADS-box gene family, while in Drosophila, homeotic genes belong to the homeobox gene family. In both Arabidopsis and Drosophila, members of the Polycomb gene family control expression of these divergent homeotic genes. How do Polycomb genes control expression of two very different sets of homeotic genes?arrow_forward
- Expression of recombinant proteins in yeast is an important tool for biotechnology companies that produce new drugs for human use. In an attempt to get a new gene X expressed in yeast, a researcher has integrated gene X into the yeast genome near a telomere. Will this strategy result in good expression of gene X? Why or why not? Would the outcome of this experiment differ if the experiment had been performed in a yeast line containing mutations in the H3 or H4 histone tails?arrow_forwardAurora AAurora A is a protein that acts as a kinase (transfers phosphates to molecules). Many types of cancer cells, including breast cancer cells, have higher than normal levels of this protein.Expressions of Aurora A genes in normal breast tissues (n = 10), normal tissues adjacent to tumors (n = 12) and breast tumors (n = 14).Scientists studying the production of Aurora A protein in normal frog cells observed that the amount of this protein in the cells changed throughout the cell cycle.Scientists tested chemicals that block Aurora 2 to see if they could be used as anti-cancer drugs. They found that some of the candidate drugs did slow the growth of cancer cells in cell culture in the lab. But when they tested these drugs in cancer patients to see if the drugs could slow the growth of solid tumors, they found that the benefit to patients was small when compared to the development of severe side effects such as anemia (low red blood cell count) and leukopenia (low white blood cell…arrow_forwardYou are interested in the effects of mutations on the expression of a human protein- encoding gene expressed in skin cells. The gene has one intron that is 450 nucleotides long. After this intron is removed from the pre-mRNA, the mRNA transcript is 1100 nucleotides in length. Diploid somatic cells have two copies of this gene. Predict the size and amount of mRNA from the cytosol of skin cells, which were obtained from the following individuals: • Individual 1: Normal individual with no mutations in this gene. • Individual 2: Homozygous for a deletion that removes the -10 to -100 region of the gene that encodes this mRNA. • Individual 3: Heterozygous in which one gene is normal and the other gene has a deletion that removes the -10 to -100 region. • Individual 4: Homozygous for a five-nucleotide deletion in the intron that removes the GT sequence at the 5' splice site. Explain your answers.arrow_forward
- Help me pleasearrow_forwardWhich of the following applies to the female sex determination in Drosophila melanogaster fruit flies? (Mark all that apply) When the X:A ratio is 1.0, the SXL gene is transcribed during the early embryonic stages. The SXL protein inhibits the expression of female differentiaion genes The SXL protein promotes the correct splicing of the Tra pre-mRNA so that functional Tra protein is made. The presence of the SXL protein promotes the correct splicing of the SXL pre-mRNA during later embryonic stages to ensure to continuous production of SXL protein. The Tra protein will stimulate the expression of male-specific genes.arrow_forwardFlowering Locus C (FLC) is a gene that is responsible for flowering in certain plants. FLC is normally expressed in new seedlings, which prevents flowering. When a plant is exposed to cold temperatures, FLC expression decreases and the plant produces flowers. FLC is regulated through epigenetic modifications. Based on this information, you should expect which of the following in histone proteins near the FLC gene: 1.In new seedlings, histones will be acetylated; while in the cold, histone methylation occurs 2.In new seedlings, histones will be methylated; while in the cold, histone acetylation occurs 3.In new seedlings, histones will be methylated; while in the cold, histone deacetylation occursarrow_forward
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