Lecture 13 Evo Dev

Overview of Evolution and Development

• Evolution and Development (Evo-Devo) studies the evolution of organisms through changes in development and form.

Diversity of Forms in Evolution

• Microevolution: Changes at the species level through gene alterations.

• Macroevolution: Larger-scale effects based on changes in body modules.

Macroevolutionary Changes and Modules

• Modules: Parts of an organism that can change independently without affecting other functions.

• Changes can occur via Molecular Parsimony: Simple gene duplications followed by redifferentiation of function.

Enhancer Elements in Gene Expression

• Enhancer elements activate particular sets of genes together.

• They regulate gene expression spatially and temporarily.

Mechanisms of Gene Expression Change

• Molecular Parsimony: Gene duplication followed by divergence leads to different gene functions.

• Duplicated genes can diverge, develop new functions, or lose function.

Gene Duplication Process

• A → A B: Subfunctionalization allows different functions.

• Neofunctionalization: New functions arise from duplicated genes.

• Gene Loss or Degeneration: Duplicated genes may become non-functional.

Activity on Gene Duplication

• Spoon Gene Activity: Explore potential changes in duplicated gene functions like neofunctionalization or subfunctionalization.

Definitions of Gene Relatedness

• Homolog: A gene related due to evolution; can be orthologs (separated by speciation) or paralogs (from duplication).

• Orthologs: Genes in different species from a common ancestor.

• Paralogs: Genes within the same genome that arose from a duplication event.

Comparison of Orthologs and Paralogs

• Orthologs: Usually maintain similar functions over time.

• Paralogs: Often gain new functions or become pseudogenes.

Signal Transduction Pathways**

• Examples of homologous pathways in mammals, flies, and plants with similar setups but different functions.

Homeotic Genes: Hox Genes

• Hox genes determine body part identity; each segment is specified by a unique set of Hox genes.

• All homeotic genes possess the homeobox segment necessary for transcription factor function.

Plant Homeotic Genes in Flower Development

• Development structures depend on expressed transcription factors during different phases.

Mechanisms of Macroevolution Changes

• Heterotopy: Change of expression location.

• Heterochrony: Change of expression timing.

• Heterometry: Change in expression amount.

• Heterotypy: Change in the kind or functional properties of proteins.

Examples of Change in Expression Location (Heterotopy)

• Hox gene duplications can lead to changes in body segment identity across species.

Impact of Hox Genes on Organ Development

• Vertebrates show evolution of limb development while arthropods retain different segment structures due to Hox gene expression.

Change of Expression Timing (Heterochrony)

• Temporal changes in expression can drastically impact development plans.

Growth Rate Changes Based on Expression Levels

• Differential expression can lead to significant anatomical differences, for example, in skull morphology among species.

Expression Amount Variation (Heterometry)

• Changes in expression levels can lead to dramatic differences in trait development, as seen in Darwin's finches and BMP4 expression.

Change in Functional Properties of Proteins (Heterotypy)

• Sequence comparisons in Ubx show how insertions can affect protein function and development.

Appendage Development in Insects

• Investigations into ancient multi-legged phenotypes using manipulation of Ubx and AbdA genes, showing that adaptation can reverse changes in limb reduction.

Evo/Dev Patterns of Change

• Summary of the types of evolutionary changes:

  • Heterotopy: Changes in location.

  • Heterochrony: Changes in timing.

  • Heterometry: Changes in amount.

  • Heterotypy: Changes in function.