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Genetic Variation

Genetic Variation

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, which...

Comparing Copy Number Variations and SNPs

Comparing Copy Number Variations and SNPs

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%...

Mutation, Gene Flow, and Genetic Drift

Mutation, Gene Flow, and Genetic Drift

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).

Principles of Pharmacogenetics: Types of Genetic Variants

Principles of Pharmacogenetics: Types of Genetic Variants

The human genome is over 99.9% identical between individuals, yet genetic differences exist at millions of bases. The human genome contains approximately 3 million variant positions per individual, many of which are heterozygous, contributing to genetic diversity and individual traits. Genetic variations include single-nucleotide polymorphisms (SNPs), insertions, deletions, and copy number variations (CNVs).SNPs, the most common variation, involve single-base changes in DNA. These can be...

Single Nucleotide Polymorphisms-SNPs

Single Nucleotide Polymorphisms-SNPs

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,...

What is Population Genetics?

What is Population Genetics?

A population is composed of members of the same species that simultaneously live and interact in the same area. When individuals in a population breed, they pass down their genes to their offspring. Many of these genes are polymorphic, meaning that they occur in multiple variants. Such variations of a gene are referred to as alleles. The collective set of all the alleles within a population is known as the gene pool.

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Related Experiment Video

Updated: May 12, 2026

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Genomic variation: what does it mean?

Marian Reiff¹, Barbara A Bernhardt, Surabhi Mulchandani

¹Center for the Integration of Genetic Healthcare Technologies, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA.

LDI Issue Brief

|April 25, 2013

Summary

This summary is machine-generated.

New genomic testing detects more genetic variations in children, aiding diagnoses for developmental delays and autism. However, some chromosomal variations remain unexplained, posing interpretation challenges for clinicians and families.

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Following the Dynamics of Structural Variants in Experimentally Evolved Populations

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An Allele-specific Gene Expression Assay to Test the Functional Basis of Genetic Associations

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Fluorescence-microscopy Screening and Next-generation Sequencing: Useful Tools for the Identification of Genes Involved in Organelle Integrity

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Published on: April 13, 2012

Area of Science:

Genetics
Pediatrics
Medical Diagnostics

Background:

Advanced genomic technologies offer 50-100x greater resolution for detecting genomic variation.
These advancements can explain up to 20% of developmental delays, autism, or congenital anomalies in children.
Unexplained chromosomal variations are also detected, raising questions about clinical significance.

Purpose of the Study:

To examine uncertainties surrounding chromosomal microarray testing.
To address the challenges in interpreting and explaining complex genetic test results.
To provide insights into the new standard of care for genetic testing in children with unexplained anomalies.

Main Methods:

Review of studies on chromosomal microarray testing.
Analysis of the interpretation and clinical significance of detected genomic variations.
Examination of the impact of rapid technological advancement on genetic testing practices.

Main Results:

Chromosomal microarray testing is the new standard for genetic testing in children with unexplained anomalies.
New technologies detect more genomic variations, aiding diagnosis in a significant percentage of cases.
A subset of detected chromosomal variations have unknown clinical significance, creating diagnostic uncertainty.

Conclusions:

The rapid advancement in genomic technology presents challenges in interpretation and patient understanding.
Further research is needed to clarify the clinical significance of unexplained chromosomal variations.
Effective communication strategies are crucial for clinicians explaining complex genetic test results to patients and families.