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Related Concept Videos

Comparing Copy Number Variations and SNPs02:26

Comparing Copy Number Variations and SNPs

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Sequencing of the human genome has opened up several best-kept secrets of the genome. Scientists have identified thousands of genome variations that exist within a population. These variations can be a single nucleotide or a larger chromosomal variation.
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
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Genetic Variation01:25

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Genetic variation is the diversity in DNA sequences found among individuals of the same species. This diversity is crucial for a species' survival because it helps organisms adapt to environmental changes. Genetic variation begins with fertilization, where an egg and sperm cell merge. Each of these cells carries 23 chromosomes, up to 46 in the fertilized egg. Chromosomes are long DNA strands that contain genes, the basic units of heredity.
Genes exist in different versions called alleles,...
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Single Nucleotide Polymorphisms-SNPs01:05

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A single nucleotide polymorphism or SNP is a single nucleotide variation at a specific genomic position in a large population. It is the most prevalent type of sequence variation found in the human genome. Point mutations that occur in more than 1% of the population qualify as SNPs. These are present once every 1000 nucleotides on an average in the human genome. Replacement of a purine with another purine (A/G) or a pyrimidine with another pyrimidine (C/T) is known as a transition. In contrast,...
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Mutation, Gene Flow, and Genetic Drift01:09

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In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).
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Background and Environment Affect Phenotype02:27

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Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
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Position-effect Variegation02:32

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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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In Vivo Modeling of the Morbid Human Genome using Danio rerio
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How does genetic variation modify ND-CNV phenotypes?

Thomas J Dinneen1, Fiana Ní Ghrálaigh2, Ruth Walsh1

  • 1Department of Psychiatry, Trinity College Dublin, Dublin, Ireland.

Trends in Genetics : TIG
|August 8, 2021
PubMed
Summary

Rare copy-number variants (CNVs) linked to neurodevelopmental disorders (NDDs) show variable effects. Other genetic factors, or "other hits," help explain these differences, offering potential for better diagnostics and treatments for NDD-CNV carriers.

Keywords:
copy number variantneurodevelopmental disorderother hit

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Determining the Likelihood of Variant Pathogenicity Using Amino Acid-level Signal-to-Noise Analysis of Genetic Variation
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Area of Science:

  • Genetics
  • Neurobiology
  • Developmental Biology

Background:

  • Rare copy-number variants (CNVs) are associated with neurodevelopmental disorders (NDDs).
  • ND-CNVs exhibit incomplete penetrance, leading to diverse carrier phenotypes.
  • Variable expressivity of ND-CNVs suggests the influence of additional genetic factors.

Purpose of the Study:

  • To review recent findings on "other hits" modifying ND-CNV expressivity.
  • To discuss current questions and future challenges in "other hits" research.
  • To explore the potential of "other hits" for improved diagnostics and therapeutics in ND-CNV carriers.

Main Methods:

  • Literature review of recent research on ND-CNVs and "other hits".
  • Discussion of genetic mechanisms underlying variable expressivity.
  • Analysis of implications for clinical applications.

Main Results:

  • "Other hits," including rare and common variants, contribute to the phenotypic heterogeneity of ND-CNVs.
  • These additional genetic factors can modify NDD risk and clinical outcomes.
  • Understanding "other hits" is crucial for explaining incomplete penetrance.

Conclusions:

  • "Other hits" research is vital for comprehending ND-CNV variability.
  • Identifying these modifying variants can enhance clinical diagnostics for NDDs.
  • Targeting "other hits" may lead to novel therapeutic strategies for ND-CNV carriers.