Bank voles adapting to diverse environments through gene conversion.

The Beta-Globin Gene's Secret: How 'Hide-and-Seek' Evolution Helps Animals Adapt

Avery Sinclair in Science & Nature December 2025 • 4 min read.

"Gene conversion: A clever genetic strategy that transfers beneficial mutations between genes, allowing for rapid adaptation to changing environments."

In the world of evolution, adapting to different environments is a constant challenge. Recent studies show that rather than waiting for new mutations, nature often uses existing genetic variations. These variations, if they help in one environment but not in another, can be a valuable source of functional variability for a species.

Hemoglobin (Hb), the protein in red blood cells that carries oxygen, is a great example. Variations in the genes that code for Hb subunits have been linked to fitness differences in various organisms. More than just carrying oxygen, Hb can also act as a crucial antioxidant, with reactive cysteine (Cys) residues playing a key role.

This article delves into a fascinating study on bank voles (Clethrionomys glareolus) and their beta-globin genes. It uncovers how a process called gene conversion helps these creatures adapt to fluctuating environmental conditions, offering insights into the mechanisms of physiological adaptation.

The Beta-Globin Gene Story: A Tale of Two Genes and Environmental Adaptation

Bank voles adapting to diverse environments through gene conversion.

Bank voles in Britain exhibit a fascinating north-south split in their beta-globin genes. There are two variants: one with serine (Ser) and one with cysteine (Cys). Kotlík and colleagues found that voles with the Cys variant (Hb F) had increased resistance to free radicals in their red blood cells compared to those with the Ser variant (Hb S). This suggested that the geographic distribution of these variants was driven by natural selection related to environmental oxidative stress.

To understand if this pattern held true across Europe, researchers examined the Ser/Cys polymorphism in bank voles throughout the continent. They looked for correlations between environmental factors and the frequency of the Cys allele, expecting that spatially variable environmental selection would influence the polymorphism.

The Study's Approach: The researchers analyzed 518 voles from 136 sites across Europe.
Genetic Analysis: They genotyped the beta-globin genes to identify Ser/Cys variants.
Environmental Data: They gathered temperature and rainfall data to identify correlations.
Statistical Modeling: They used PCA and Samßada to reduce data complexity and correct for population structure.

The study found that the Cys allele is widespread in Europe, with its frequency varying by location. The distribution of the Cys allele in the major beta-globin gene (HBB-T1) closely matched the distribution of the Western mitochondrial DNA lineage of bank voles. While population history is important, environmental conditions also play a role in shaping the distribution of the Cys allele.

Gene Conversion: A Mechanism for Fine-Tuning Adaptation

The research revealed that the beta-globin phenotype is mainly encoded by the major paralog HBB-T1. However, there's evidence of bidirectional gene conversion of exon 2 with the low-expression paralog HBB-T2. This means that genetic information is being exchanged between the two genes.

The data supports a model where gene conversion reshuffles genotypes between the high- and low-expressed paralogs. This allows for tuning of erythrocyte thiol levels, helping to maintain intracellular redox balance under fluctuating environmental conditions.

This study highlights a possible role for gene conversion between differentially expressed gene duplicates as a mechanism of physiological adaptation. By shuffling genetic material, populations can better adapt to new or changing environments, showcasing the intricate ways nature enables survival.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.3390/genes9100492, Alternate LINK

Title: Playing Hide-And-Seek In Beta-Globin Genes: Gene Conversion Transferring A Beneficial Mutation Between Differentially Expressed Gene Duplicates

Subject: Genetics (clinical)

Journal: Genes

Publisher: MDPI AG

Authors: Michaela Strážnická, Silvia Marková, Jeremy Searle, Petr Kotlík

Published: 2018-10-12

Everything You Need To Know

What is gene conversion and how does it help animals adapt to their environments?

Gene conversion is a genetic process where one gene's sequence is replaced by the sequence of another similar gene. In bank voles, this process allows for the transfer of beneficial mutations, like the cysteine variant in the beta-globin genes, between different gene copies. This enables rapid adaptation to environmental changes, such as oxidative stress, by spreading advantageous traits quickly within the population.

Which animal and genes were studied to understand how they adapt to different environments and where did the study take place?

The study focused on bank voles (Clethrionomys glareolus) and their beta-globin genes. Researchers examined the distribution of two variants, one with serine (Ser) and one with cysteine (Cys), in the beta-globin genes of bank voles across Europe. They analyzed genetic data from 518 voles across 136 sites, correlating the presence of the Cys variant with environmental factors like temperature and rainfall, to understand how these genetic variations contribute to the voles' adaptation to different environments.

What are the different variants of the beta-globin genes found in bank voles, and what advantages do they offer?

The beta-globin genes in bank voles have two main variants: one with serine (Ser), referred to as Hb S, and another with cysteine (Cys), referred to as Hb F. The Cys variant (Hb F) provides increased resistance to free radicals, acting as a crucial antioxidant, which helps bank voles cope with environmental oxidative stress. The geographic distribution of these variants is influenced by natural selection, where the Cys allele is more common in areas with higher oxidative stress.

Which specific paralogs are involved in gene conversion, and what part of the gene is exchanged?

The research indicates that the beta-globin phenotype is primarily encoded by the major paralog HBB-T1 in bank voles. However, gene conversion occurs between HBB-T1 and the low-expression paralog HBB-T2, specifically involving exon 2. This bidirectional gene conversion allows for the exchange of genetic information, potentially fine-tuning the adaptation of bank voles to environmental conditions by transferring beneficial mutations between the two beta-globin genes.

How does population history relate to the distribution of the Cys allele in bank voles, and what environmental factors are also important?

The distribution of the Cys allele in the HBB-T1 gene of bank voles closely matches the distribution of the Western mitochondrial DNA lineage of these voles. This suggests a complex interplay between population history and environmental selection. While the spread of mitochondrial DNA lineages provides a historical context, environmental conditions, such as oxidative stress levels, play a significant role in shaping the distribution of the Cys allele. These factors together drive the adaptation of bank voles across different regions of Europe.