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Ch. 21 - Genomic Analysis
Chapter 20, Problem 24

Dominguez et al. (2004) suggest that by studying genes that determine growth and tissue specification in the eye of Drosophila, much can be learned about human eye development.

What evidence suggests that genetic eye determinants in Drosophila are also found in humans? Include a discussion of orthologous genes in your answer.

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span>Begin by explaining the concept of orthologous genes. Orthologous genes are genes in different species that evolved from a common ancestral gene by speciation. They often retain the same function across species.</span
span>Discuss the significance of Drosophila (fruit fly) as a model organism in genetic studies. Drosophila is widely used due to its genetic similarities to humans, short life cycle, and ease of genetic manipulation.</span
span>Highlight specific genes involved in eye development that are conserved between Drosophila and humans. For example, the 'eyeless' gene in Drosophila is orthologous to the 'PAX6' gene in humans, both playing crucial roles in eye development.</span
span>Explain how studies in Drosophila have shown that mutations in these genes can lead to similar developmental issues in both flies and humans, providing evidence of their conserved function.</span
span>Conclude by emphasizing that the presence of orthologous genes and their conserved functions across species supports the idea that studying Drosophila can provide insights into human eye development.</span

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Orthologous Genes

Orthologous genes are genes in different species that evolved from a common ancestral gene through speciation. They typically retain the same function across species, making them crucial for comparative studies in genetics. In the context of eye development, identifying orthologous genes between Drosophila and humans can provide insights into conserved genetic pathways that govern similar biological processes.
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Gene Function Conservation

Gene function conservation refers to the phenomenon where genes maintain similar roles across different organisms throughout evolution. This concept is significant in genetics as it allows researchers to infer the function of human genes based on studies conducted in model organisms like Drosophila. Evidence of conserved functions in eye development genes suggests that mechanisms governing eye formation may be similar in both species.
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Developmental Genetics

Developmental genetics is the field of study that focuses on how genes control the growth and development of organisms. It encompasses the genetic regulation of developmental processes, including organ formation. By examining the genetic determinants of eye development in Drosophila, researchers can uncover fundamental principles that may also apply to human eye development, highlighting the importance of model organisms in understanding complex biological systems.
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Related Practice
Textbook Question
Homology can be defined as the presence of common structures because of shared ancestry. Homology can involve genes, proteins, or anatomical structures. As a result of 'descent with modification,' many homologous structures have adapted different purposes. Under what circumstances might one expect proteins of similar function to not share homology? Would you expect such proteins to be homologous at the level of DNA sequences?
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Textbook Question

Yeager, M., et al. [(2007) Nature Genetics 39:645–649] and Sladek, R., et al. [(2007) Nature 445:881–885] have used single-nucleotide polymorphisms (SNPs) in genome-wide association studies (GWAS) to identify novel risk loci for prostate cancer and Type 2 diabetes, respectively. Each study suggests that disease-risk genes can be identified that significantly contribute to the disease state. Given your understanding of such complex diseases, what would you determine as reasonable factors to consider when interpreting the results of GWAS?

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Textbook Question
Comparisons between human and chimpanzee genomes indicate that a gene that may function as a wild-type or normal gene in one primate may function as a disease-causing gene in another [The Chimpanzee Sequencing and Analysis Consortium (2005). Nature 437:69–87]. For instance, the PPARG locus (regulator of adipocyte differentiation) is a wild-type allele in chimps but is clearly associated with Type 2 diabetes in humans. What factors might cause this apparent contradiction? Would you consider such apparent contradictions to be rare or common? What impact might such findings have on the use of comparative genomics to identify and design therapies for disease-causing genes in humans?
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Textbook Question

Dominguez et al. (2004) suggest that by studying genes that determine growth and tissue specification in the eye of Drosophila, much can be learned about human eye development.

What evidence indicates that the eyeless gene is part of a developmental network?

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Textbook Question
Genomic sequencing has opened the door to numerous studies that help us understand the evolutionary forces shaping the genetic makeup of organisms. Using databases containing the sequences of 25 genomes, scientists examined the relationship between GC content and global amino acid composition [Kreil, D. P., and Ouzounis, C. A. (2001) Nucl. Acids Res. 29:1608–1615]. They found that it is possible to identify thermophilic species on the basis of their amino acid composition alone, which suggests that evolution in a hot environment selects for a certain whole organism amino acid composition. In what way might evolution in extreme environments influence genome and amino acid composition? How might evolution in extreme environments influence the interpretation of genome sequence data?
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Textbook Question

Whole-exome sequencing (WES) is helping physicians diagnose a genetic condition that has defied diagnosis by traditional means. The implication here is that exons in the nuclear genome are sequenced in the hopes that, by comparison with the genomes of nonaffected individuals, a diagnosis might be revealed.

What are the strengths and weaknesses of this approach?

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