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Restarting Stalled Replication Forks

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart,...

Meiosis I

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...

Meiosis I

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...

Nondisjunction

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...

Nondisjunction

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.

Mutations

Mutations

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Related Experiment Video

Updated: Mar 7, 2026

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila

Published on: August 20, 2019

Mutations in DONSON disrupt replication fork stability and cause microcephalic dwarfism.

John J Reynolds¹, Louise S Bicknell², Paula Carroll²

¹Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK.

Nature Genetics

|February 14, 2017

Summary

This summary is machine-generated.

Downstream neighbor of SON (DONSON) is a novel DNA replication fork protection factor. Mutations in DONSON cause microcephalic dwarfism by impairing DNA replication and genome stability.

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Optogenetic Random Mutagenesis Using Histone-miniSOG in C. elegans

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Area of Science:

Molecular Biology
Genetics
Cell Biology

Background:

Efficient genome duplication relies on factors that manage DNA replication forks.
Replication fork instability can lead to DNA damage and genomic instability.

Purpose of the Study:

Identify novel DNA replication fork protection factors.
Investigate the role of DONSON in DNA replication and its link to microcephalic dwarfism.

Main Methods:

Genetic mutation analysis in patients with microcephalic dwarfism.
Cellular assays to assess DNA replication fork stability and DNA damage.
Analysis of ATM- and Rad3-related (ATR)-dependent signaling pathways.

Main Results:

DONSON identified as a novel replication fork protection factor and replisome component.
Biallelic DONSON mutations found in 29 individuals with microcephalic dwarfism.
DONSON deficiency causes replication-associated DNA damage, impaired ATR signaling, and chromosomal instability.

Conclusions:

Mutations in DONSON are a common cause of microcephalic dwarfism.
DONSON is essential for mammalian DNA replication fork stability and genome integrity.