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Gene Evolution - Fast or Slow?

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The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
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Gene Evolution - Fast or Slow?

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Related Experiment Video

Updated: Jun 30, 2026

The Drosophila Imaginal Disc Tumor Model: Visualization and Quantification of Gene Expression and Tumor Invasiveness Using Genetic Mosaics

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Microevolutionary support for a developmental hourglass: gene expression patterns shape sequence variation and

Tami Cruickshank¹, Michael J Wade

¹Biology Department, Indiana University, Bloomington, IN, USA. tcruicks@indiana.edu

Evolution & Development

|September 23, 2008

Summary

Maternal-effect genes show higher genetic variation within species and greater divergence between species than other developmental genes. This explains the "developmental hourglass" pattern in evolution.

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Published on: December 19, 2011

Area of Science:

Evolutionary Developmental Biology (Evo-Devo)
Population Genetics
Molecular Developmental Genetics

Background:

Evo-Devo aims to integrate genotype-phenotype dynamics with microevolutionary processes.
Understanding sequence variation in developmental genes is key to evolutionary insights.

Purpose of the Study:

To analyze sequence variation across five gene classes in Drosophila early embryo development.
To connect within-species genetic variation to between-species divergence.
To investigate the "developmental hourglass" model using gene sequence data.

Main Methods:

Comparative sequence variation analysis of maternal, gap, pair-rule, segment polarity, and segment identity genes in Drosophila.
Examining both microevolutionary (within-species) and macroevolutionary (between-species) patterns.

Main Results:

Maternal-effect genes exhibit 2-3 fold higher relative sequence variation within species.
Maternal-effect genes show 2-4 fold greater relative sequence divergence among species.
Findings align with microevolutionary theory predictions.

Conclusions:

Relaxed selective constraint on maternal-effect genes allows wider exploration of mutational and phenotypic space.
Maternal-effect genes broaden the "base" of the developmental hourglass, while later-acting zygotic genes narrow the "waist".
Genes with both maternal and zygotic expression show the strongest evolutionary constraint, obscuring hourglass patterns.