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The bicoid gene is a coordinate maternal–effect gene. A female that is homozygous for a loss-of-function bicoid allele is mated to a wild-type male. What are the phenotypes of their progeny?
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Ch. 18 - Developmental Genetics
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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TOC.tableOfContents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
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Capitolo 18, Problema 14
Given that maternal Bicoid activates the expression of hunchback, what would be the consequence of adding extra copies of the bicoid gene by transgenic means to a wild-type female with two copies, thus creating a female fly with three or four copies of the bicoid gene? How would the hunchback expression be altered? What about the expression of other gap genes and pair-rule genes?
Guida verificata passo dopo passo1
Understand the role of the Bicoid gene: Bicoid is a maternal effect gene that establishes the anterior-posterior axis in Drosophila embryos. It acts as a transcription factor, activating the expression of target genes like hunchback in a concentration-dependent manner.
Analyze the effect of adding extra copies of the bicoid gene: Adding extra copies of the bicoid gene will increase the amount of Bicoid protein produced in the embryo. This will result in a higher concentration of Bicoid protein along the anterior-posterior axis.
Predict the impact on hunchback expression: Since hunchback expression is activated by Bicoid in a concentration-dependent manner, the increased Bicoid protein levels will shift the threshold of hunchback activation further toward the posterior of the embryo. This means hunchback will be expressed in a broader region of the embryo.
Consider the effect on other gap genes: Gap genes, such as Kruppel and knirps, are also regulated by Bicoid and other factors. The altered Bicoid gradient will likely shift the expression domains of these genes, as their activation and repression thresholds depend on the Bicoid concentration. This could lead to changes in the spatial patterning of these genes.
Evaluate the impact on pair-rule genes: Pair-rule genes, which are regulated by the combined inputs of gap genes and other factors, will also be affected. Changes in the expression patterns of gap genes will alter the regulatory inputs to pair-rule genes, potentially shifting their expression patterns and affecting the segmentation of the embryo.
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Bicoid Protein Function
Bicoid is a maternal effect protein that plays a crucial role in early embryonic development in Drosophila. It acts as a transcription factor that activates the expression of target genes, such as hunchback, in a concentration-dependent manner. The presence of Bicoid establishes the anterior-posterior axis of the embryo, influencing the patterning of segments.
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05:05
Proteins
Hunchback Gene Regulation
Hunchback is a gap gene that is activated by Bicoid in the anterior region of the Drosophila embryo. It is essential for proper segmentation and the development of body structures. The expression of hunchback is sensitive to the concentration of Bicoid; thus, increasing Bicoid levels through transgenic means could lead to altered hunchback expression, potentially resulting in abnormal segmentation patterns.
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09:22Review of Regulation
Gap Genes and Pair-Rule Genes Interaction
Gap genes, including hunchback, are responsible for defining broad regions of the embryo, while pair-rule genes refine this pattern into alternating segments. The expression of gap genes influences the activation of pair-rule genes, which are crucial for establishing the segmental organization of the embryo. Changes in gap gene expression due to altered Bicoid levels could disrupt the normal regulatory cascade, affecting the expression of pair-rule genes and leading to segmentation defects.
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07:56Interacting Genes Overview
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Domanda del libro di testo
The pair-rule gene fushi tarazu is expressed in the seven even-numbered parasegments during Drosophila embryogenesis. In contrast, the segment polarity gene engrailed is expressed in the anterior part of each of the 14 parasegments. Since both genes are active at similar times and places during development, it is possible that the expression of one gene is required for the expression of the other. This can be tested by examining expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Given the hierarchy of gene action during Drosophila embryogenesis, what might you predict to be the result of these experiments?
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Domanda del libro di testo
The pair-rule gene fushi tarazu is expressed in the seven even-numbered parasegments during Drosophila embryogenesis. In contrast, the segment polarity gene engrailed is expressed in the anterior part of each of the 14 parasegments. Since both genes are active at similar times and places during development, it is possible that the expression of one gene is required for the expression of the other. This can be tested by examining the expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Based on your prediction, can you predict the phenotype of the fushi tarazu and engrailed double mutant?
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Domanda del libro di testo
The bicoid gene is a coordinate maternal–effect gene. If loss of bicoid function in the egg leads to lethality during embryogenesis, how are females homozygous for bicoid produced? What is the phenotype of a male homozygous for bicoid loss-of-function alleles?
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Domanda del libro di testo
The bicoid gene is a coordinate maternal-effect gene.
A female Drosophila heterozygous for a loss-of-function bicoid allele is mated to a male that is heterozygous for the same allele. What are the phenotypes of their progeny?
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Domanda del libro di testo
What phenotypes do you expect in flies homozygous for loss-of-function mutations in the following genes: Krüppel, odd-skipped, hedgehog, and Ultrabithorax?
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