BIO 234—Fundamental Evolutionary Biology

Scottsdale Community Collegeand 2 + 2 partnership with

Northern Arizona University

Lecture 6.1Evolution and Development

Dr. John D. Nagy

Summary and Instructions

Complete this lecture by performing the following exercises:

1. Study §13.1 through 13.3 (pages 463–480).

2. Optional: Read §13.4 for an interesting example of gene duplication’s role in developmentof vertebrate neural crest cells. This provides 2 nice examples of the concepts introducedin this chapter.

3. Master the definitions of terms in the vocabulary list below.

4. Answer the focus questions written below; you may submit your answers either throughCanvas or via email as a pdf or jpeg.

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Vocabulary

Homeotic genes Ontogeny Neoteny Developmental accelerationSegmentation genes Heterochrony Progenesis HypermorphosisHomeobox genes Enhancers Silencers ParalogsGene duplication Subfunctionalization Neofunctionalization

Focus Questions

Answer the following questions in Canvas. Alternatively, you can answer them in your ownmedia (for example, paper, OneNote, or Word) and submit them through Canvas via email.Please note: If you choose to submit via email, please submit a pdf or jpeg copy of your work.Use your own words and be thorough in all your free-response answers.

Concepts

1. Compare and contrast the Meckel-Serres Law, von Baer’s law, and Haeckel’s biogeneticlaw. But sure to state each “law” before treating their similarities and differences.

2. Compare and contrast the processes of development your textbook refers to as recapitu-lation and paedomorphosis. Describe, using proper terminology, the ways in which theseprocesses can occur.

3. Explain what it means when biologists say that Hox genes exhibit colinearity.

4. Bill McGinnis and colleagues inserted the Hox-2.2 gene from mice into fruit flies (Drosophilamelanogaster). Describe why they performed this experiment, and what the outcome was.

5. Compare and contrast homeobox and MADS-box genes as thoroughly as you can.

6. What type of proteins do Hox and Mads-box genes code for? What do these proteins do,according to the book? Specifically, where do they bind and what effect do they have?

7. The following is a quote from a paper on the specificity of Hox genes (i.e., the exacttissues in which they act and their precise functions) by Zandvakili and Gebelein (2016):

“Metazoans encode clusters of paralogous Hox genes that are critical for properdevelopment of the body plan.”

Explain precisely what these authors mean by “clusters of paralogous Hox genes.”

8. Compare and contrast subfunctionalization and neofunctionalization of duplicated genes.

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Synthesis

1. Reconsider the experiment performed by McGinnis et al. that you wrote about in ConceptQuestion 4. Based on those results, would you predict that the Hox-2.2 gene in miceand Antp gene in fruit flies are homoplastic or homologous? Explain your reasoningthoroughly.

2. Develop a hypothesis suggesting what types of genes were acted on by natural selection,and how their functions were altered, causing the loss of a tail in apes, including humans.Rely heavily on the information in this lecture’s readings, and explain your reasoningthoroughly.

Figure 1: Fetal hemoglobin (Hbs, left) vs. adult hemoglobin (Hbb, right).

Figure 2: Two clusters of globin genes found on the short arms of chromosomes 11 (β-cluster;top) and 16 (α-cluster; bottom).

3. Hemoglobins in human fetuses and adults differ. Adult hemoglobin (Hbb) is a tetramer of 2α-globin chains and 2 β-globin chains, whereas fetal hemoglobin (Hbs) has 2 α- and 2 γ-globinchains (Fig. 1). The α- and β-globins are members of a cluster of globin genes scattered onchromosomes 11 and 16 (Fig. 2). Use the concepts from §13.3 of the textbook to explain bothwhy there are so many nearly-identical globin genes in the human genome, and how naturalselection caused there to be different combinations of globins in adult and fetal humans. Thebest answer will use the professional terminology introduced in this section.

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Image Credits

Figure, page 1: Source: Thewissen et al. (2009).

References

Thewissen, J. G. M., L. N. Cooper, J. C. George, and S. Bajpai (2009). From land to water:The origin of whales, dolphins, and porpoises. Evo. Edu. Outreach 2, 272–288.

Zandvakili, A. and B. Gebelein (2016). Mechanisms of specificity for hox factor activity. J.Dev. Biol. 4, 16.

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