insight - Genetics - # Facultative Parthenogenesis Mechanism

Mechanism of Facultative Parthenogenesis in Whiptail Lizard Species

Q: Implications of mixoploidy on the development and fitness of FP animals

Mixoploidy, characterized by a combination of haploid and diploid cells in FP animals, has significant implications for their development and fitness. The presence of haploid cells can lead to abnormal development due to the genetic imbalance caused by having only one set of chromosomes. This imbalance can result in various developmental defects such as misaligned jaws, missing limbs, failed abdominal closure, and craniofacial abnormalities. Additionally, mixoploidy exposes deleterious recessive alleles that were previously masked by heterozygosity. As a result, some embryos may not develop at all or exhibit severe malformations that impact their survival post-hatching.

Q: Presence of haploid cells contributing to abnormal development in FP organisms

The presence of haploid cells in FP organisms plays a crucial role in contributing to abnormal development. When embryonic development initiates with consecutive divisions of unfertilized haploid oocytes followed by skipped mitosis leading to homozygous diploid cells and mixoploidy throughout the organism's tissues. Haploid cells lack the necessary genetic material for normal cellular function and tissue formation which results in aberrant growth patterns and structural abnormalities during organogenesis. These abnormalities manifest as physical deformities like agenesis of eyes, limb malformations, misaligned jaws among others observed in FP animals.

Q: Understanding FP mechanisms aiding conservation efforts for species with dwindling populations

Understanding the mechanisms underlying facultative parthenogenesis (FP) can significantly aid conservation efforts for species with dwindling populations through several key ways: Genetic Purging: By eliminating most deleterious alleles within a single generation through genome-wide homozygosity resulting from FP. Reproductive Assurance: Providing an alternative reproductive strategy when mate encounters are infrequent or population bottlenecks occur. Population Resilience: Increasing resilience against the effects of population bottlenecks and reducing genetic load within small populations. Selective Breeding Programs: Utilizing knowledge about FP mechanisms to maintain existing gene pools effectively during captive breeding programs. Species Survival: Enhancing understanding enables better management strategies aimed at conserving genetically diverse populations essential for long-term species survival amidst environmental challenges. By leveraging insights into how facultative parthenogenesis functions at a molecular level, conservation biologists can implement targeted strategies focused on maintaining genetic diversity while mitigating risks associated with reduced population sizes or limited mating opportunities within endangered species' habitats

Core Concepts

Facultative parthenogenesis in whiptail lizards is driven by a post-meiotic mechanism, resulting in genome-wide homozygosity and mixoploidy.

Abstract

Facultative parthenogenesis (FP) has been observed in various vertebrates, including whiptail lizards. The underlying mechanism involves post-meiotic genome duplication, leading to homozygous animals from haploid oocytes. Contrary to previous beliefs, FP can occur alongside sexual reproduction and is not triggered by isolation from mating partners. Mixoploidy was observed in FP animals, with some showing developmental defects due to the exposure of deleterious alleles. Genome-wide homozygosity exposes genetic load but also purges non-functional alleles, contributing to genetic purification and potential adaptive advantages.

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biorxiv.org

Stats

A. marmoratus genome size estimated at 1.67 Gb.
Whole-genome sequencing revealed genome-wide homozygosity in FP animals.
RAD-seq analysis identified low heterozygosity rates (<0.05%) in natural populations.

Quotes

"FP leads to a precipitous reduction in genetic diversity as only one set of alleles is inherited."
"Mixoploidy and genome-wide homozygosity come at a price, exposing deleterious alleles."
"FP may be an adaptive trait aiding in genetic purification and resilience against population bottlenecks."

Key Insights Distilled From

Post-meiotic mechanism of facultative parthenogenesis in gonochoristic whiptail lizard species

by Ho,D. V., To... at www.biorxiv.org 09-22-2023

https://www.biorxiv.org/content/10.1101/2023.09.21.558237v1

Deeper Inquiries

Implications of mixoploidy on the development and fitness of FP animals

Mixoploidy, characterized by a combination of haploid and diploid cells in FP animals, has significant implications for their development and fitness. The presence of haploid cells can lead to abnormal development due to the genetic imbalance caused by having only one set of chromosomes. This imbalance can result in various developmental defects such as misaligned jaws, missing limbs, failed abdominal closure, and craniofacial abnormalities. Additionally, mixoploidy exposes deleterious recessive alleles that were previously masked by heterozygosity. As a result, some embryos may not develop at all or exhibit severe malformations that impact their survival post-hatching.

Presence of haploid cells contributing to abnormal development in FP organisms

The presence of haploid cells in FP organisms plays a crucial role in contributing to abnormal development. When embryonic development initiates with consecutive divisions of unfertilized haploid oocytes followed by skipped mitosis leading to homozygous diploid cells and mixoploidy throughout the organism's tissues. Haploid cells lack the necessary genetic material for normal cellular function and tissue formation which results in aberrant growth patterns and structural abnormalities during organogenesis. These abnormalities manifest as physical deformities like agenesis of eyes, limb malformations, misaligned jaws among others observed in FP animals.

Understanding FP mechanisms aiding conservation efforts for species with dwindling populations

Understanding the mechanisms underlying facultative parthenogenesis (FP) can significantly aid conservation efforts for species with dwindling populations through several key ways:

Genetic Purging: By eliminating most deleterious alleles within a single generation through genome-wide homozygosity resulting from FP.
Reproductive Assurance: Providing an alternative reproductive strategy when mate encounters are infrequent or population bottlenecks occur.
Population Resilience: Increasing resilience against the effects of population bottlenecks and reducing genetic load within small populations.
Selective Breeding Programs: Utilizing knowledge about FP mechanisms to maintain existing gene pools effectively during captive breeding programs.
Species Survival: Enhancing understanding enables better management strategies aimed at conserving genetically diverse populations essential for long-term species survival amidst environmental challenges.

By leveraging insights into how facultative parthenogenesis functions at a molecular level, conservation biologists can implement targeted strategies focused on maintaining genetic diversity while mitigating risks associated with reduced population sizes or limited mating opportunities within endangered species' habitats