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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.
Gene Conversion02:08

Gene Conversion

Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
Nondisjunction01:29

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.
Nondisjunction01:21

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...
Genome Copying Errors02:46

Genome Copying Errors

DNA replication is a well-evolved process that copies millions of base pairs with high fidelity during each cell division. Occasionally a wrong base or a long stretch of wrong bases may get added to the daughter strands. If the errors are left unchecked, cells might accumulate several mutations that might endanger their  survival. Therefore, the copying errors are checked and repaired at three levels.
The Ratio of X Chromosome to Autosomes02:45

The Ratio of X Chromosome to Autosomes

In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.  
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...

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Related Experiment Video

Updated: Jun 13, 2026

An Array-based Comparative Genomic Hybridization Platform for Efficient Detection of Copy Number Variations in Fast Neutron-induced Medicago truncatula Mutants
09:32

An Array-based Comparative Genomic Hybridization Platform for Efficient Detection of Copy Number Variations in Fast Neutron-induced Medicago truncatula Mutants

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Introductory comments on special section-genomic microduplications: When adding may equal subtracting.

Carlos A Bacino1, Sau-Wai Cheung

  • 1Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. cbacino@bcm.tmc.edu

American Journal of Medical Genetics. Part A
|April 29, 2010
PubMed
Summary
This summary is machine-generated.

Interpreting copy number variations (CNVs) detected by array comparative genomic hybridization (aCGH) is challenging. Differentiating pathogenic CNVs from benign polymorphisms requires systematic collection and public sharing of phenotypic data.

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Area of Science:

  • Genetics
  • Genomic Medicine
  • Bioinformatics

Background:

  • Array-based comparative genomic hybridization (aCGH) enables detection of copy number variations (CNVs) down to single exons.
  • Interpreting the clinical significance of detected CNVs, particularly copy number gains, presents a major challenge in clinical practice.

Purpose of the Study:

  • To highlight the difficulties in distinguishing pathogenic CNVs from nonpathogenic polymorphisms.
  • To emphasize the critical need for systematic collection and public accessibility of phenotypic data linked to CNVs.

Main Methods:

  • The study discusses the challenges associated with interpreting CNVs identified through aCGH.
  • It reviews the distinction between pathogenic CNVs and population polymorphisms.
  • It underscores the importance of phenotypic data integration.

Main Results:

  • Copy number gains from genomic rearrangements are often harder to interpret than losses.
  • Many CNVs are polymorphic and unrelated to disease, complicating clinical assessment.
  • Differentiating disease-causing CNVs from benign variants is a significant clinical hurdle.

Conclusions:

  • Systematically collecting and depositing phenotypic information associated with CNVs into searchable, public databases is crucial.
  • This approach will aid clinicians in differentiating pathogenic CNVs from nonpathogenic polymorphisms.
  • Improved data sharing is essential for advancing the clinical utility of aCGH technology.