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Lampbrush Chromosomes

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...

Lampbrush Chromosomes

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, Rückert observed LBCs in shark egg cells and coined the term "lampbrush chromosomes" because they looked like brushes used to clean kerosene lamps.
LBCs are made up of two pairs of conjugating homologous chromatids. Each chromatid consists of alternatively positioned regions of condensed-inactive chromatin and loosely placed-active side loops, which can be contracted and extended. The loops resemble the...

Hedgehog Signaling Pathway

Hedgehog Signaling Pathway

The Hedgehog gene (Hh) was first discovered due to its control of the growth of disorganized, hair-like bristles phenotype in Drosophila, much like hedgehog spines. Hh plays a crucial role in the development of organs and the maintenance of homeostasis in both invertebrates and vertebrates. However, while Drosophila has only one Hh protein, mammals have multiple functional Hedgehog proteins - Sonic (Shh), Desert (Dhh), and Indian Hedgehog (Ihh). All of these homologous proteins have adapted to...

Hedgehog Signaling Pathway

Hedgehog Signaling Pathway

The Hedgehog gene (Hh) was first discovered due to its control of the growth of disorganized, hair-like bristles phenotype in Drosophila, much like hedgehog spines. Hh plays a crucial role in the development of organs and the maintenance of homeostasis in both invertebrates and vertebrates. However, while Drosophila has only one Hh protein, mammals have multiple functional Hedgehog proteins - Sonic (Shh), Desert (Dhh), and Indian Hedgehog (Ihh). All of these homologous proteins have adapted to...

Synteny and Evolution

Synteny and Evolution

John H. Renwick first coined the term “synteny” in 1971, which refers to the genes present on the same chromosomes, even if they are not genetically linked. The species with common ancestry tend to show conserved syntenic regions. Therefore, the concept of synteny is nowadays used to describe the evolutionary relationship between species.
Around 80 million years ago, the human and mice lineages diverged from the common ancestor. During the course of evolution, the ancestral chromosome underwent...

Evolutionary Relationships through Genome Comparisons

Evolutionary Relationships through Genome Comparisons

Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is that if two species share a common feature, it is likely encoded by the DNA sequence conserved between both species. The advent of genome sequencing technologies in the late 20th century enabled scientists to understand the concept of conservation of domains between species and helped them to deduce evolutionary relationships across diverse...

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Related Experiment Video

Updated: Jul 6, 2026

Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

Published on: January 12, 2015

The amphioxus Hox cluster: characterization, comparative genomics, and evolution.

Chris T Amemiya¹, Sonja J Prohaska, Alicia Hill-Force

¹Benaroya Research Institute at Virginia Mason, Seattle, Washington, USA.

Journal of Experimental Zoology. Part B, Molecular and Developmental Evolution

|March 21, 2008

Summary

The amphioxus Hox cluster, crucial for chordate development, shows a highly derived posterior region. This suggests vertebrate Hox clusters evolved through regulatory DNA streamlining after genome duplication.

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Last Updated: Jul 6, 2026

Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

Expression of Fluorescent Proteins in Branchiostoma lanceolatum by mRNA Injection into Unfertilized Oocytes

Published on: January 12, 2015

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Ablation of a Single Cell From Eight-cell Embryos of the Amphipod Crustacean Parhyale hawaiensis

Ablation of a Single Cell From Eight-cell Embryos of the Amphipod Crustacean Parhyale hawaiensis

Published on: March 16, 2014

Area of Science:

Evolutionary Developmental Biology
Comparative Genomics
Chordate Evolution

Background:

The amphioxus (Branchiostoma floridae) Hox cluster is considered archetypal for chordates.
Understanding Hox gene organization provides insights into vertebrate evolution.

Purpose of the Study:

To describe the 448 kb amphioxus Hox cluster region (Hox14 to Hox1).
To analyze conserved noncoding regulatory elements within the amphioxus Hox cluster.
To investigate the evolutionary origins of Hox gene duplications and organization.

Main Methods:

Genomic sequencing of the amphioxus Hox cluster.
Analysis of complete coding sequences for all 14 amphioxus Hox genes.
Identification and analysis of conserved noncoding regulatory elements.

Main Results:

The posterior amphioxus Hox cluster is highly derived, obscuring orthology with gnathostomes.
The anterior Hox cluster region is significantly more conserved.
Amphioxus and gnathostome Hox clusters exclude repetitive elements, unlike protostome clusters.

Conclusions:

The amphioxus Hox cluster provides a unique model for chordate Hox gene evolution.
The derived nature of the posterior region challenges simple orthology assignments.
Vertebrate Hox cluster reduction likely resulted from regulatory DNA streamlining post-genome duplication.