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Related Concept Videos

Meiosis I01:49

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...
Karyotyping01:17

Karyotyping

Overview
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.
Meiosis I03:09

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...
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...

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In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
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Understanding the basis for Down syndrome phenotypes.

Randall J Roper1, Roger H Reeves

  • 1Department of Physiology at Johns Hopkins University School of Medicine, and at McKusick-Nathans Institute for Genetic Medicine, Baltimore, Maryland, United States of America.

Plos Genetics
|April 6, 2006
PubMed
Summary
This summary is machine-generated.

Down syndrome, caused by trisomy 21, involves over 350 genes. Understanding genotype-phenotype interactions is key to developing strategies that can ameliorate its developmental effects.

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Area of Science:

  • Genetics and developmental biology
  • Human genetics
  • Molecular biology

Background:

  • Down syndrome is a genetic disorder resulting from trisomy of human Chromosome 21.
  • The condition is characterized by a collection of features arising from the over-expression of genes on Chromosome 21.
  • Developmental and functional divergences in individuals with trisomy 21 are complex and likely involve multiple genetic mechanisms.

Purpose of the Study:

  • To explore genotype-phenotype interactions in Down syndrome.
  • To develop working concepts for ameliorating the effects of trisomy 21.
  • To understand the genetic underpinnings of developmental divergence in trisomy 21.

Main Methods:

  • Analysis of genotype-phenotype correlations.
  • Review of genetic mechanisms contributing to Down syndrome.
  • Conceptual framework development for therapeutic strategies.

Main Results:

  • Elevated transcript levels of Chromosome 21 genes are a primary cause of Down syndrome features.
  • Multiple genetic mechanisms contribute to the diverse developmental and functional outcomes in trisomy 21.
  • Genotype-phenotype interactions offer insights into potential therapeutic targets.

Conclusions:

  • Understanding the complex interplay between genes and phenotypes in Down syndrome is crucial.
  • Developing effective strategies to ameliorate Down syndrome requires a comprehensive approach to genetic mechanisms.
  • Further research into genotype-phenotype interactions can guide the development of targeted interventions.