Hypomorphic alleles of a pleiotropic gene essential for early development can sometimes provide enough gene activity for an organism to survive early development. In such cases, the mutant
Mice homozygous for null alleles of Fgf8 (fibroblast growth factor 8) die during early embryogenesis, obscuring a later role for Fgf8 in setting up left/right asymmetry of organs. However, mice homozygous for hypomorphic Fgf8 alleles, develop much further and reveal that Fgf8 protein is a determinant of leftness. In Fgf8 mutants, many organs such as the heart are left/right reversed as shown in the following figure.
How might these Fgf8 hypomorphic mutant alleles been generated? (More than one answer is possible.)
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Genetics: From Genes to Genomes, 5th edition
- The phenotype of a heterozygous mouse (Aa) is agouti. The agouti banding pattern is due to altered expression of the agouti gene. Which of the following statement is false? a) Expression of the agouti gene inhibits the production of eumelanin. b) Evidence suggests that the agouti gene is only expressed in tissues associated with fur production. c) Epigenetic markers silence the agouti gene resulting in dark pigmentation at the tip and root of the hair. d) All of the abovearrow_forwardIn Metastatic Breast Cancer [such as in Breast Invasive Ductal Carcinoma; Breast Invasive Carcinoma, NOS; Breast Invasive Cancer, NOS; Invasive Breast Carcinoma; Breast Invasive Lobular Carcinoma; Breast Mixed Ductal and Lobular Carcinoma] what role does the genes Tp53 and Tp63 have? Would one of them affect the other (i.e. mutation, etc) or there is not relationship among the two genes at all.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_forward
- a) What is the role of the Hox genes in animal development and what types of phenotypes do you see in mutations of Hox genes? Provide an example of a mutant phenotype of a Hox gene in Drosophila. 3mrks The Hox genes are known to act in combination. Panel A in figure below shows the normal expression patterns of the bithorax complex, and segments that align with the expression patterns. Panel B shows the segmental phenotypes in mutants for both abdominal - A and Abdominal - B, panel C shows the phenotypes in mutants for Abdominal - B, and panel D shows the phenotypes in mutants for Ultrabithorax. b) Describe how the segmental phenotypes illustrate the combinatorial action of Hox genes (you can ignore A9 as it is patterned by the terminal patterning system). 4mrks A) Parasegments 11 12 13 14 B) D) 10 11 12 13 14 Segments A2 A3 A4 A5 Abdominal-B abdominal-A Ultrabithorax T1 12 13 A1 11 12 12 12 A2 A3 A4 Aarrow_forwardPax6 is a gene that is involved in mammalian eye development. Mutations in this gene result in a lack of iris in humans, and mice that are homozygous for the mutation lack eyes completely. Mutations in the eyeless gene in the fruitfly Drosophila result in reduced eyes. Expressing Pax6 from mammals in other tissues of Drosophila during its embryonic development can result in an ectopic eye (e.g. an eye expressed in a different tissue type). An example of an ectopic eye on the antenna of Drosophila is shown below. Part A: The eye of humans, mouse, and fly are an example of the following (check all that apply) A. Structural analog B. Structural homolog C. Developmental homolog D. Genetic homolog Part B: Darwin's hypothesis of natural selection has two components: Species are not static but change through time Species are related, and not independent. In what ways does the human, mouse, and fly eye support or contradict one or both of the two components of…arrow_forwardAlpha-1 antitrypsin has codominant inheritance. M genes express normal levels. S and Z genes have low expression. Which of the following is most likely to develop emphyema? A person with: 1) two M genes who does smoke 2) two S genes who does smoke 3) one M and one S gene who does not smoke 4) one M gene and one S gene who does smoke 5) two M genes who does not smoke 6) two S genes who does not smokearrow_forward
- Answer the following questions based on the information given below: Act>CD2>Gal4 is a Flip-out construct that will express CD2 under the control of the ubiquitous Actin promoter in the absence of FLP. Expression of FLP will cause excision of the CD2 cassette so that GAL4 will be expressed instead. Suppose you identified a new gene X and generated UAS-X flies. In an experiment to examine the possible functions of X in eye development, you used flies with the following genotype: HsFLP; Act>CD2>Gal4, UAS-GFP / +; UAS-X /+ After a brief heat shock to induce FLP expression, you went on to examine eye discs for cells that express gene X. How can you identify cells that have the expression of gene X? (1 point) I would identify cells that have the expression of gene X through an Epistatic screen in the following image, you stained eye disc with antibodies against atonal (shown in Red), Elav (shown in blue), and GFP (shown in green). The yellow arrows point to the…arrow_forwardAcquired mutation in the p53 gene is the most common genetic alteration found in human cancer (> 50% of all cancers). A germline mutation in p53 is the causative lesion of Li- Fraumeni familial cancer syndrome. In many tumors, one p53 allele on chromosome 17p is deleted and the other is mutated. What type of protein is encoded by the p53 gene? (A) Caspase (B) DNA repair enzyme (C) Membrane cell adhesion molecule (D) Serine phosphatase (E) Telomerase (F) Transcription factor (G) Tyrosine kinasearrow_forwardIn mice, the A allele causes agouti fur, the AY allele causes yellow fur and is dominant to the A allele. The homozygous AY AY genotype is lethal. Why is the AYAY homozygous condition lethal? The yellow pigment produced by A allele is required for survival. The AY allele lacks an upstream merc gene which is required for normal embryonic development. The AY allele highly transcribes the merc gene which is lethal in a homozygous AYAY individual. The AY allele contains a null mutation in the A gene, which is required for normal embryonic development. None of the other answers are correct.arrow_forward
- The C-myc gene is a proto-oncogene which is highly expressed in breast tissue and appears to cause proliferation of breast tissue and its elevated expression is associated with breast cancer. Based just on the ChIP data from the previous questions (also shown below), which of the three drugs (estrogen, tamoxifen and raloxifene) would you recommend for treating breast cancer? Justify your response and explain the potential side effects of each drug.arrow_forwardDescribe the common signal transduction event that is perturbed by cancer-promoting mutations in the genes encoding RAS and NF-1. Why are mutations in RAS more commonly found in cancers than mutations in NF-1?arrow_forwardMembers of a family are affected by a hereditary inflammatory and immunodeficiency disease. The disease phenotype was due to a mutation in the PLCG2 gene, determined by comparing an affected father and an affected daughter, both heterozygotes, with the homozygous unaffected mother (Zhou et al, 2012). The wild-type protein acts to regulate various immune and inflammatory pathways within the cell. The variant protein is over expressed (more abundant), leading to increased intracellular signaling and leading to increased inflammation and reduced immunity in the affected people. Select all the statements below that can be correctly applied to this system. [Hint: There are FOUR.] O co-dominance dominant negative mutant allele O gain-of-function mutation O haplosufficent wildtype allele O haploinsuffient wildtype allele O leaky mutant allele O loss-of-function mutation O null mutant allele O partial dominance O simple dominance O the mutant allele is hypermorphic O the mutant allele is…arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage LearningBiology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning