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Related Concept Videos

Gene Duplication and Divergence02:37

Gene Duplication and Divergence

The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was  generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are characterized.
Regulation of Expression Occurs at Multiple Steps02:24

Regulation of Expression Occurs at Multiple Steps

Gene expression can be regulated at almost every step from gene to protein. Transcription is the step that is most commonly regulated. This involves the binding of proteins to short regulatory sequences on the DNA. This association can either promote or inhibit the transcription of a gene associated with the respective sequence.
Transcription results in the generation of precursor (pre-mRNA) that consists of both exons and introns, which needs further processing before being translated to a...
Regulation of Expression Occurs at Multiple Steps02:24

Regulation of Expression Occurs at Multiple Steps

Gene expression can be regulated at almost every step from gene to protein. Transcription is the step that is most commonly regulated. This involves the binding of proteins to short regulatory sequences on the DNA. This association can either promote or inhibit the transcription of a gene associated with the respective sequence.
Transcription results in the generation of precursor (pre-mRNA) that consists of both exons and introns, which needs further processing before being translated to a...
Regulation of Expression at Multiple Steps01:23

Regulation of Expression at Multiple Steps

The gene expression in cells is regulated at different stages: (i) transcription, (ii) RNA processing, (iii) RNA localization, and (iv) translation. Transcriptional regulation is mediated by regulatory proteins such as transcription factors, activators, or repressors—these control gene expression by initiating or inhibiting the transcription of genes. Once a precursor or pre-mRNA is produced, it undergoes post-transcriptional modification, including 5' capping, splicing, and the addition of a...
Cis-regulatory Sequences02:02

Cis-regulatory Sequences

Cis-regulatory sequences are short fragments of non-coding DNA that are present on the same chromosomes as the genes that they regulate. These fragments serve as binding sites for transcriptional regulators, proteins that are responsible for controlling gene transcription and differential gene expression across cell types in eukaryotes. Cis-regulatory sequences can be close to the gene of interest or thousands of bases away in the DNA sequence; however, those sequences that are further away are...
Position-effect Variegation02:32

Position-effect Variegation

In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.

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Related Experiment Video

Updated: Jun 6, 2026

Inherent Dynamics Visualizer, an Interactive Application for Evaluating and Visualizing Outputs from a Gene Regulatory Network Inference Pipeline
10:44

Inherent Dynamics Visualizer, an Interactive Application for Evaluating and Visualizing Outputs from a Gene Regulatory Network Inference Pipeline

Published on: December 7, 2021

Gene expression divergence recapitulates the developmental hourglass model.

Alex T Kalinka1, Karolina M Varga, Dave T Gerrard

  • 1Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.

Nature
|December 15, 2010
PubMed
Summary
This summary is machine-generated.

The hourglass model suggests animal development diverges most early and late. This study reveals gene expression is most conserved during the phylotypic period, supporting natural selection

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Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps

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A Semi-high-throughput Imaging Method and Data Visualization Toolkit to Analyze C. elegans Embryonic Development

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Related Experiment Videos

Last Updated: Jun 6, 2026

Inherent Dynamics Visualizer, an Interactive Application for Evaluating and Visualizing Outputs from a Gene Regulatory Network Inference Pipeline
10:44

Inherent Dynamics Visualizer, an Interactive Application for Evaluating and Visualizing Outputs from a Gene Regulatory Network Inference Pipeline

Published on: December 7, 2021

Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps
11:52

Temporal Ordering of Dynamic Expression Data from Detailed Spatial Expression Maps

Published on: February 9, 2017

A Semi-high-throughput Imaging Method and Data Visualization Toolkit to Analyze C. elegans Embryonic Development
06:49

A Semi-high-throughput Imaging Method and Data Visualization Toolkit to Analyze C. elegans Embryonic Development

Published on: October 29, 2019

Area of Science:

  • Developmental biology
  • Evolutionary biology
  • Genomics

Background:

  • The embryonic phylotypic period is characterized by maximal morphological similarity across animal phyla.
  • The hourglass model proposes that embryogenesis diverges most in early and late stages, with mid-embryogenesis showing peak conservation.
  • While morphological data support the hourglass model, the role of gene expression evolution in this pattern remains unclear.

Purpose of the Study:

  • To investigate the extent to which gene expression evolution underlies the morphological hourglass pattern.
  • To determine if gene expression is maximally conserved during the arthropod phylotypic period.

Main Methods:

  • Utilized species-specific microarrays for six sequenced Drosophila species with evolutionary distances up to 40 million years.
  • Quantified gene expression divergence across different embryonic developmental stages.
  • Applied evolutionary models to analyze gene expression patterns and identify selective pressures.

Main Results:

  • Gene expression was found to be maximally conserved during the arthropod phylotypic period, aligning with the hourglass model.
  • Over 80% of genes analyzed best fit evolutionary models incorporating stabilizing selection at each time point.
  • Selective constraint on gene expression was maximized during the phylotypic period for genes with conserved optimal expression levels.
  • Genes exhibiting the strongest hourglass pattern are involved in crucial developmental processes.

Conclusions:

  • Natural selection actively conserves gene expression patterns during mid-embryogenesis.
  • Provides genome-wide evidence for the molecular basis of the developmental hourglass pattern.
  • Highlights the role of conserved gene expression in constraining the evolution of animal body plans.