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Mutations

Mutations

Mutations

Mutations

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...

Viral Mutations

Viral Mutations

A mutation is a change in the sequence of bases of DNA or RNA in a genome. Some mutations occur during replication of the genome due to errors made by the polymerase enzymes that replicate DNA or RNA. Unlike DNA polymerase, RNA polymerase is prone to errors because it is not capable of “proofreading” its work. Viruses with RNA-based genomes, like HIV, therefore accrue mutations faster than viruses with DNA-based genomes. Because mutation and recombination provide the raw material...

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).

Mutations in Microorganisms

Mutations in Microorganisms

Mutations are heritable changes in an organism’s genome involving alterations in the base sequence of DNA or RNA. These changes can influence cellular processes and phenotypic traits, potentially transforming the unaltered wild type into a mutant form. Such changes, termed forward mutations, are pivotal in shaping the genetic diversity of organisms.RNA viruses exhibit the highest mutation rates due to the absence of robust proofreading mechanisms during genome replication. In contrast,...

Point and Frameshift Mutations

Point and Frameshift Mutations

Point mutations are genetic alterations involving the change of a single nucleotide base pair in DNA. Depending on how the alteration affects protein synthesis, they can lead to various consequences.Point mutations fall into the following types:Silent mutations occur when a nucleotide change does not alter the amino acid sequence due to the redundancy of the genetic code. For instance, changing ACC to ACA still encodes threonine, leaving the protein function unaffected. This occurs because...

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Related Experiment Video

Updated: Feb 14, 2026

Introducing Point Mutations into Human Pluripotent Stem Cells Using Seamless Genome Editing

Introducing Point Mutations into Human Pluripotent Stem Cells Using Seamless Genome Editing

Published on: May 10, 2020

Smith-Lemli-Opitz Mutations in Unexplained Stillbirths.

Karen J Gibbins¹, Uma M Reddy², George R Saade³

¹Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Utah Health, Salt Lake City, Utah.

American Journal of Perinatology

|February 13, 2018

Summary

Smith-Lemli-Opitz syndrome (SLOS) mutations were assessed in unexplained stillbirths. Only 0.7% of stillbirths carried DHCR7 mutations, suggesting no strong link between unrecognized mutations and stillbirth.

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Last Updated: Feb 14, 2026

Introducing Point Mutations into Human Pluripotent Stem Cells Using Seamless Genome Editing

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Quantification of Colonic Stem Cell Mutations

Quantification of Colonic Stem Cell Mutations

Published on: September 25, 2015

Area of Science:

Genetics
Biochemistry
Reproductive Medicine

Background:

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder caused by defects in cholesterol biosynthesis due to mutations in the 7-dehydrocholesterol reductase (DHCR7) gene.
While 3% of Caucasians are carriers of DHCR7 mutations, the incidence of SLOS is significantly lower than theoretically predicted, suggesting other factors may influence its manifestation.
The discrepancy between carrier frequency and SLOS incidence prompted an investigation into the role of DHCR7 mutations in unexplained stillbirths.

Purpose of the Study:

To investigate the prevalence of 7-dehydrocholesterol reductase (DHCR7) mutations in cases of unexplained stillbirth.
To determine if unrecognized DHCR7 mutations contribute significantly to stillbirths.

Main Methods:

A prospective, multicenter, population-based case-control study was conducted, analyzing stillbirths and a sample of live births.
DNA was extracted from placental tissue of 144 unexplained stillbirths with adequate quality DNA.
Exons 3 to 9 of the DHCR7 gene were sequenced to identify mutations.

Main Results:

Of 139 analyzed stillbirths, 6.5% (9 cases) had a single DHCR7 mutation in coding exons 3-9.
One case (0.7%) was a compound heterozygote for DHCR7 mutations but showed no clinical or histologic features of SLOS.
Overall, DHCR7 mutations were detected in only 0.7% of the unexplained stillbirth cohort.

Conclusions:

The study found a low prevalence (0.7%) of 7-dehydrocholesterol reductase (DHCR7) mutations in unexplained stillbirths.
These findings do not support a strong association between unrecognized DHCR7 mutations and stillbirth.
Further research may be needed to explore other genetic or environmental factors contributing to unexplained stillbirths.