To analyze:
The activity of RNA polymerase II is inhibited by Actinomycin D. When actinomycin D is present, early development in many vertebrate species, for example frogs, can begin after the formation of a blastula (hollow ball of cells that forms after early cleavage divisions), but development stops before gastrulation. Question asked to discuss the activity of maternal gene in contrast to activity of zygotic gene in early frog development.
Introduction:
Drosophila is the model organism of study of development. It is a well studied genome sequence. Multiple genes are involved in the development of drosophila. The gene that directs the development and fate of an organism are known as developmental genes. Bicoid and Nanos are maternal effect genes; the egg receives these from the mother. Bicoid and Nanos play an important role in creating the anterior to posterior axis. The genes are activated in the fertilized egg (Zygote). In contrast to maternal effect genes, these genes are transcribed by zygotic DNA.
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Genetic Analysis: An Integrated Approach (2nd Edition)
- Nanos is a strict maternal-effect gene in Drosophila; that is not transcribed in the embryo. Mutations in nanos result in the loss of posterior structures in the embryo. Predict the phenotype (i.e. wild type or mutant) of the following embryos.arrow_forwardImagine a scenario in which prenatal testing of a human female fetus indicates that the baby will have a normal XX karyotype but is heterozygous for a mutation that inactivates the Xist promoter. Allele “Xr” represents the mutated version of the Xist promoter, and “XR” represents the normal version of the Xist promoter. How will this mutation affect the process of X inactivation?A. "X inactivation will still be random with both mutant and normal X chromosomes being randomly inactivated" B. "The chromosome with the mutant Xist promoter will always be active" C. "The chromosome with the mutant Xist promoter will always be inactivated" D. "The normal X chromosome (no mutation in Xist) will always be active" E. "The normal X chromosome (no mutation in Xist) will always be inactivated"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
- The oncogenic protein BETA promotes entry into the S phase of the cell cycle. Phosphorylation of BETA at the amino acid Tyr98 causes BETA to be degraded by the proteasome, thus limiting its abundance. A mutation in the codon encoding Tyr98 changes this residue to Cys, which cannot be phosphorylated. What is the best description of this mutant allele?a) antimorphb) hypermorphc) hypomorphd) amorphe) neomorpharrow_forwardAnother way to study the role of proteins (e.g., transcription factors) that function in development is to microinject the mRNA that encodes a protein, or the purified protein itself, into an oocyte or embryo, and then determine how this affects the subsequent development of the embryo, larva, and adult. For example, if Bicoid protein is injected into the posterior region of an oocyte, the resulting embryo will develop into a larva that has anterior structures at both ends. Based on your understanding of the function of each developmental gene, what would be the predicted phenotype if the following proteins or mRNAs were injected into normal oocytes? A. Nanos mRNA injected into the anterior end of an oocyte B. Antp protein injected into the posterior end of an embryo C. Toll mRNA injected into the dorsal side of an early embryoarrow_forward“In an organism that reproduces asexually, there is no difference between a somatic cell mutation and a germ line mutation.” Is this statement true? Explain.arrow_forward
- Drosophila females homozygous for loss-of-functionmutations in the gene aubergine are sterile. RNA-Seqexperiments show that in the ovaries of these females,the levels of RNAs for many kinds of transposable elements are more than 10× higher than in wild-type ovaries. The aubergine gene encodes a Piwi-family protein.a. Why do you think these females are sterile?b. Piwi proteins interact with piRNAs that are transcribed from piRNA gene clusters. Given that thelevels of many kinds of TEs are elevated in mutantovaries, what kinds of DNA sequences do youthink are located in these clusters?c. Many investigators think of piRNAs as a kind ofdefensive mechanism that protects organisms fromthe effects of new transposable elements that mightbe introduced into genomes, for example fromother species. Explainarrow_forwardYou found a strain of mutant fruit flies (Drosophila) living on the rotten bananas in your dorm room. You notice that many of the larvae have abnormal abdominal segments. You want to know if the “abdomenless” mutation is a maternal effect gene. Describe an experiment you would do to determine this, and the results that would support and contradict the notion that the abdomenless gene encodes a maternal determinant.arrow_forwardA C. elegans (nematode) gene called par-1 helps todetermine the AP axis of the animal early in development. Scientists determined that par-1 is pleiotropic—it also has a later function in forming the vulva of theadult animal. How could researchers circumvent thelethality of par-1− mutants to observe the later function of the par-1 gene? (Hint: C. elegans larvae caneat bacteria expressing RNAi for any gene.)arrow_forward
- The Drosophila gene Sex lethal (Sxl) is deserving of itsname. Certain alleles have no effect on XY animals butcause XX animals to die early in development. Other alleles have no effect on XX animals but cause XY animals to die early in development. Thus, some Sxl allelesare lethal to females, while others are lethal to males.a. Would you expect a null mutation in Sxl to causelethality in males or in females? b. Why do Sxl alleles of either type cause lethality ina specific sex?The gene transformer (tra) gets its name from sexualtransformation, as some tra alleles can change XXanimals into morphological males, while other traalleles can change XY animals into morphologicalfemales.c. Which of these sex transformations would becaused by null alleles of tra and which would becaused by constitutively active alleles of tra?d. In contrast with Sxl, null tra mutations do notcause lethality either in XX or in XY animals.However, the Sxl protein regulates the productionof the Tra protein. Why…arrow_forwardThe gene Igf2 for the insulin-like growth factor (IGF) promotes growth hormone production and cell proliferation, and is maternally imprited. The IGF receptor gene Igf2r counters the effects of the Igf2 gene and is paternally imprinted. In knockout experiments with mice, which combination of manipulated genes will result in mice that will grow to normal size? (a) The maternally derived Igf2r and paternally derived igf2 are both normally expressed. (b) The maternally derived Igf2r and paternally derived igf2 are both deleted. (c) The maternally derived Igf2r is normally expressed but the paternally derived Igf2 is deleted. (d) The paternally derived Igf2 is normally expressed but the maternally derived Igf2r is deleted. A. (c) and (d) B. (d) only C. (a) and (b) D. (a) onlyarrow_forwardThe GAL4 expression system can be used to experimentally induce expression of a gene in a specific tissue at a specific time. You want to study the overexpression of Your Favorite Gene (YFG) in mouse ear development. However, if you overexpress this gene everywhere, the mouse is not viable past early embryo development. You have the following mouse lines with different mutations or transgenic constructs available. Which two will you cross together to answer your research questions? GAL4 with constitutive enhancer GAL4 with embryo enhancer GAL4 with ear enhancer yfg loss-of-function line YFG CDNA with UASG promoter YFG CDNA with constitutive promoterarrow_forward
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