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Related Concept Videos

Proofreading01:31

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template DNA strand. DNA polymerase has a higher affinity to add the correct base and ensures fidelity during DNA replication. Furthermore,  it exhibits proofreading activity during replication, using an exonuclease domain that cuts off incorrect nucleotides from the nascent DNA strand.
Errors During Replication are Corrected by the DNA Polymerase Enzyme
Proofreading01:43

Proofreading

Synthesis of new DNA molecules starts when DNA polymerase links nucleotides together in a sequence that is complementary to the template DNA strand. DNA polymerase has a higher affinity for the correct base to ensure fidelity in DNA replication. The DNA polymerase furthermore proofreads during replication, using an exonuclease domain that cuts off incorrect nucleotides from the nascent DNA strand.Errors during Replication Are Corrected by the DNA Polymerase EnzymeGenomic DNA is synthesized in...
Translesion DNA Polymerases02:10

Translesion DNA Polymerases

Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
Spontaneous and Induced Mutations01:30

Spontaneous and Induced Mutations

Spontaneous mutations arise infrequently during DNA replication due to errors in the process. A key factor behind these errors is tautomeric shifts in nitrogenous bases, where bases transition from keto to enol forms or amino to imino forms. This shift can alter base-pairing rules, leading to mutations. Additionally, reactive oxygen species (ROS) arising from aerobic metabolism can damage DNA, resulting in depurination (loss of a purine base) or depyrimidination (loss of a pyrimidine base).
Point and Frameshift Mutations01:30

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...
Mutations in Microorganisms01:18

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,...

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Polymerase gamma 1 mutations: clinical correlations.

Margherita Milone1, Rami Massie

  • 1Department of Neurology, Mayo Clinic, Rochester, MN 55902, USA. milone.margherita@mayo.edu

The Neurologist
|March 12, 2010
PubMed
Summary
This summary is machine-generated.

Mutations in the POLG1 gene cause a wide range of mitochondrial diseases with diverse symptoms. Genetic testing of POLG1 is crucial for diagnosis, and sodium valproate should be avoided due to liver failure risks.

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Area of Science:

  • Genetics
  • Neurology
  • Mitochondrial Biology

Background:

  • Mitochondrial disorders stem from defects in mitochondrial DNA (mtDNA) or nuclear genes impacting mtDNA.
  • POLG1, encoding the mtDNA polymerase gamma subunit, is crucial for mtDNA replication.
  • POLG1 mutations are linked to autosomal recessive and dominant mitochondrial diseases with varied clinical presentations.

Purpose of the Study:

  • To summarize common clinical phenotypes associated with POLG1 mutations.
  • To highlight the diagnostic challenges and considerations for POLG1-related disorders.
  • To provide guidance on avoiding specific treatments detrimental to patients with POLG1 mutations.

Main Methods:

  • Review of clinical phenotypes associated with POLG1 mutations.
  • Analysis of diagnostic findings from muscle biopsies and mtDNA analysis.
  • Synthesis of conclusions regarding diagnosis and treatment.

Main Results:

  • Common phenotypes include Alpers syndrome, progressive external ophthalmoplegia, ataxia-neuropathy, and epilepsy.
  • Other manifestations include childhood encephalopathy, Parkinsonism, stroke-like events, and exercise intolerance.
  • Muscle biopsy and mtDNA analysis can be informative but are not always conclusive.

Conclusions:

  • POLG1 mutations lead to highly heterogeneous phenotypes, complicating syndrome classification.
  • A negative muscle biopsy does not rule out POLG1-related disease.
  • Molecular analysis of POLG1 is essential for suspected cases, and sodium valproate should be avoided.