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
- Protein levels and mRNA levels for a particualr gene don’t always match. For example, the GCN4 gene in yeast is always producing mRNA, but the Gcn4 protein is only made when the cells are starved. What does this mean for diagnostic techniques that try to look at gene expression?arrow_forwardAPOE gene has been found to be a major contributor to sporadic Alzheimer's disease (AD), by acting as an age-of-onset modifier for the common relatively late-onset forms of the disease. Among four alleles causing early onset of AD, the epsilon4 allele (APOE4) disrupts this function. If you generate transgenic monkeys in which the normal allele of APOE gene is knocked out, what phenotype will you expect for those knockout monkeys? A. The APE mRNA expression will be completely suppressed. B. They slow down the development of AD. C. They develop AD early. D. They don't show any AD symptom.arrow_forwardAs shown in Figure 13-26, the Sonic hedgehog gene is expressed in many places in a developing chicken. Is theidentical Sonic hedgehog protein expressed in each tissue? If so, how do the tissues develop into different structures? If not, how are different Sonic hedgehog proteinsproduced?arrow_forward
- 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
- The BMP-Nodal gradient so vital to amphibian and fish development may be critically important in other vertebrates (including humans) as well. Moreover, can any field of pluripotent cells (such as human embryonic stem cells)respond to gradients of BMP and Nodal signals?arrow_forwardMarfan syndrome is due to a mutation in a gene that encodes aprotein called fibrillin-1. It is inherited as a dominant trait. Thefibrillin-1 protein is the main constituent of extracellular microfibrils.These microfibrils can exist as individual fibers or associatewith a protein called elastin to form elastic fibers. People with thedisorder tend to be unusually tall with long limbs, and they mayhave defects in their heart valves and aorta. Let’s suppose aphenotypically unaffected woman has a child with a man whohas Marfan syndrome.A. What is the probability this child will have the disease?B. If this couple has three children, what is the probability thatnone of them will have Marfan syndrome?arrow_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_forward
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