Related Experiment Video
Updated: Jun 5, 2026
06:18
Frequency and Distribution of Crossovers in Caenorhabditis elegans Meiosis by SNP Genotyping using Real-time PCR
Published on: July 11, 2025
Incorporating experimental mortality improves statistical inference of crossover patterning along meiotic chromosomes
Spencer Koury1, Melika Ghasemi Shiran1, Eva Hammonds1
1Department of Biological Sciences, Auburn University, Room 101 Rouse Life Sciences Building, 120 W Samford Ave, Auburn, AL 36849, United States.
Genetics
|June 3, 2026
Summary
This study addresses "missing data" in fruit fly recombination experiments by developing a new model. The findings reveal significant marker-associated mortality, impacting genetic map accuracy.
Area of Science:
- Genetics
- Developmental Biology
- Population Genetics
Background:
- Classic genetic recombination studies infer crossing-over from offspring markers, introducing significant data loss in Drosophila melanogaster.
- Inferred recombination rates are biased by chromatid segregation to polar bodies and inviable offspring.
Purpose of the Study:
- To develop a probabilistic model accounting for experimental mortality in Drosophila melanogaster recombination studies.
- To improve the accuracy of genetic map construction by addressing sources of uncertainty and bias.
Main Methods:
- Extended the Cx(Co)m data-generating process with assumptions on double strand breaks, crossover maturation, and segregation.
- Quantified experimental mortality through egg counts in 6-point X chromosome testcrosses and controls.
- Utilized likelihood ratio tests to model sex-specific, marker-associated viability defects.
Main Results:
- Identified 44% overall F2 experimental mortality in a dataset of 19,927 flies.
- Demonstrated that 36% of mortality is attributable to sex-specific, marker-associated viability defects.
- Showed that X chromosome genetic map lengths vary with experimental mortality.
Conclusions:
- Differential mortality should be considered the default null hypothesis when comparing F2 recombinant fractions.
- Proposed probabilistic models enhance the characterization of meiotic crossover patterning.
- Provided power curves to guide future experimental designs for accurate genetic mapping.
Related Concept Videos
01:34Crossing Over
Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
01:30Crossing Over
Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I, duplicated...
03:09Meiosis 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...
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...
01:49Meiosis 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 a...
01:21Nondisjunction
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 sister...
01:29Nondisjunction
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.