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Polytene Chromosomes

Polytene Chromosomes

Polytene chromosomes are giant interphase chromosomes with several DNA strands placed side by side. They were discovered in the year 1881 by Balbiani in salivary glands, intestine, muscles, malpighian tubules, and hypoderm of larvae Chironomus plumosus. Hence, these are also called "Salivary gland chromosomes." These are found in insects of the order Diptera and Collembola; in certain organs of mammals; and synergids, antipodes of flowering plants. Polytene chromosomes are also regularly...

Nondisjunction

Nondisjunction

Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate correctly and move to the opposite poles of the cells. This produces daughter cells with abnormal chromosome numbers. Nondisjunction is common during anaphase I or anaphase II of meiosis. Mutations in synaptonemal complex proteins that attach homologous chromosomes increase the chances of nondisjunction in anaphase I of meiosis I. In contrast, mutations in topoisomerases and condensins that hold sister...

Nondisjunction

Nondisjunction

During meiosis, chromosomes occasionally separate improperly. This occurs due to failure of homologous chromosome separation during meiosis I or failed sister chromatid separation during meiosis II. In some species, notably plants, nondisjunction can result in an organism with an entire additional set of chromosomes, which is called polyploidy. In humans, nondisjunction can occur during male or female gametogenesis and the resulting gametes possess one too many or one too few chromosomes.

Meiosis I

Meiosis I

Meiosis is a carefully orchestrated set of cell divisions, the goal of which—in humans—is to produce haploid sperm or eggs, each containing half the number of chromosomes present in somatic cells elsewhere in the body. Meiosis I is the first such division, and involves several key steps, among them: condensation of replicated chromosomes in diploid cells; the pairing of homologous chromosomes and their exchange of information; and finally, the separation of homologous chromosomes by a...

Meiosis I

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of meiosis, where the genetic recombination of homologous chromosomes and the reduction of the ploidy level by half occurs.
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...

Meiosis I

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of meiosis, where the genetic recombination of homologous chromosomes and the reduction of the ploidy level by half occurs.
Prophase I is the most extended and complex step of meiosis I characterized by synapsis, chromosome pairing, and recombination of the homologous chromosomes. This process is facilitated by a proteinaceous structure called the...

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Related Experiment Video

Updated: May 17, 2026

Manipulation of Ploidy in Caenorhabditis elegans

Manipulation of Ploidy in Caenorhabditis elegans

Published on: March 15, 2018

Monkeying around with ploidy.

Richard J A Buggs¹

¹School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK. r.buggs@qmul.ac.uk

Molecular Ecology

|October 19, 2012

Summary

Whole genome duplication (WGD) is common in plants, but its evolutionary impact is unclear. New research highlights recently evolved allopolyploid monkey flowers, offering insights into WGD processes and genetic diversity in plant evolution.

Area of Science:

Plant evolutionary biology
Genomics
Ecology

Background:

Whole genome duplication (WGD) is a frequent event in plant evolution, yet the factors driving its occurrence and its subsequent effects on genomes remain poorly understood.
Identifying and studying recently formed allopolyploid species is crucial for understanding the evolutionary consequences of WGD.
Documentary evidence for recent polyploid formation is rare, limiting our understanding of these events.

Purpose of the Study:

To investigate the evolutionary processes and pathways associated with whole genome duplication (WGD) in plants.
To explore the ecological, biogeographical, and genetic factors that contribute to WGD events in nature.
To examine the impact of WGD on gene expression and genome evolution in newly formed polyploid species.

Main Methods:

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Last Updated: May 17, 2026

Manipulation of Ploidy in Caenorhabditis elegans

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Identification and naming of new allopolyploid species, such as Mimulus peregrinus.
Utilizing historical records and meticulous botanical surveys to establish the recent origin of polyploids.
Analyzing genetic diversity in recently discovered allopolyploids, like Mimulus sookensis.

Main Results:

The discovery and naming of Mimulus peregrinus, an allopolyploid monkey flower with evidence of a recent origin (<140 years).
The genus Mimulus is emerging as a valuable model system for studying ecological genetics.
New data reveal high genetic diversity within the recently discovered allopolyploid Mimulus sookensis.

Conclusions:

The discovery of young allopolyploids like Mimulus peregrinus provides critical opportunities to study the immediate effects of WGD.
Further research on recently formed polyploids is essential to generalize findings about WGD in plant evolution.
The study of monkey flower allopolyploids contributes significantly to understanding rapid evolutionary adaptation and genetic diversity following WGD.