GENETIC MODIFICATION OF RECOMBINATION RATE IN TRIBOLIUM CASTANEUM

ABSTRACT Asymmetrical responses were obtained in a replicated study of 15 generations of two-way selection for recombination rate between the ruby (rb) and jet (j) loci in Tribolium castaneum. Recombination rates in the two replicate high lines increased from an average of 0.22 in the base populations to an average of 0.42 at generation 15. Recombination rate pooled over the 15 generations of selection in each low line was significantly less than the control but there was no clear downward trend in response to selection for decreased recombination rate. The realized heritabilities were 0.16 ± 0.03 and 0.17 ± 0.02 in the two high lines, and were not significantly different from zero in the two low lines. Selection was based on crossing over in cis females only; however, rates measured in cis males after 12 generations showed the same response patterns as female rates. Similar response patterns were also determined for recombination measured in trans males and females at generation 18 following three generations of relaxed selection. The distribution of recombination rates measured in backcross beetles [(H × L) × H and (H × L) × L] at generation 12 indicated polygenic control with those genes decreasing recombination rate being dominant. Detailed analysis of recombination rates in F1's produced by interline crosses at generation 15 confirmed the directional dominance findings. Under a polygenic model of recombination modifiers in which low recombination is dominant to high, average recombination rates will increase as inbreeding progresses, thus providing a mechanism for the production of new gene combinations in small populations.

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THE GENETIC SYSTEM CONTROLLING RECOMBINATION IN THE SILKWORM

Genetics ◽

10.1093/genetics/99.2.231 ◽

1981 ◽

Vol 99 (2) ◽

pp. 231-245

Author(s):

Hiroyasu Ebinuma ◽

Narumi Yoshitake

Keyword(s):

Chromosomal Aberrations ◽

Recombination Frequency ◽

Genetic System ◽

Chromosome 2 ◽

Chromosome 5 ◽

Recombination Rates ◽

Heterozygous Condition ◽

In Trans ◽

The Mean ◽

In Cis

ABSTRACT The nature of recombination modifiers was investigated in Bombyx mori lines selected for high (H) and low (L) recombination rates between the pS and Y loci in chromosome 2. Since the mean recombination rates for the H × L and L × H F1 crosses were approximately intermediate between those of high and low lines, the cytoplasmic maternal effect and difference in the activity of recombination modifiers between marked and unmarked second chromosomes were not detected. The H × (L × H), H × (H × L), L × (L × H) and L × (H × L) backcrosses indicated the presence of additive and dominance effects of marked and unmarked second chromosomes and the remaining chromosomes.——Recombination rates between the pS and Y loci in chromosome 2 and half-nonrecombination rates between the pe and re loci in chromosome 5 of high and low lines indicated that these recombination modifiers caused changes in the recombination frequency between pS and Y in chromosome 2, but not between pe and re in chromosome 5.——There were no differences in viability between individuals having the second chromosomes of the recombinant types [pS +, pY (H); pS +, + Y (L)] and those of the nonrecombinant types [pS Y, p + (H); pS Y, + + (L)] in both high and low lines. Mean recombination rates measured in cis [pS Y/p + (H); pS Y/+ + (L)] and trans [pS +/p Y (H); pS +/+ Y (L)] males were the same in the high but not in the low line. No segregation of a single recombination modifier was indicated by the distribution of recombination rates measured in trans males [pS +/p Y (H); pS +/+ Y (L)] of high and low lines. Accordingly, the recombination modifiers distributed on chromosome 2 in the heterozygous condition were not gross chromosomal aberrations, but polygenic factors in the low line.

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Gender dysphoria and sexual euphoria - A Bayesian perspective on the influence of gender-affirming hormone therapy on sexual arousal

10.1101/2021.11.22.21266679 ◽

2021 ◽

Author(s):

Manfred Klöbl ◽

Murray Bruce Reed ◽

Patricia Handschuh ◽

Ulrike Kaufmann ◽

Melisande Elisabeth Konadu ◽

...

Keyword(s):

Sexual Orientation ◽

Hormone Therapy ◽

Sexual Arousal ◽

Response Patterns ◽

Erotic Stimuli ◽

Trans Men ◽

Subjective Sexual Arousal ◽

In Trans ◽

Trans Women ◽

In Cis

While the concept of sexual orientation is more clearly defined in cisgender, this is less so in transgender individuals. Both experienced gender and sex hormones have a relation to sexual preferences, arousal in response to erotic stimuli, and thus sexual orientation. In transgender individuals sexual orientation occasionally changes before or during transition, which may involve gender-affirming hormone therapy. Using functional magnetic resonance imaging, we investigated whether the neuronal and behavioral patterns of sexual arousal in transgender individuals moved from the given (before) to their chosen gender after 4.5 months of hormone therapy. To this aim, trans women and men as well as age-matched cisgender controls rated visual stimuli showing heterosexual, lesbian or gay intercourse for subjective sexual arousal. Utilizing a Bayesian framework allowed us to incorporate behavioral findings in cisgender individuals of different sexual orientations. The hypothesized changes in response patterns could indeed be observed in the behavioral responses to the single but not the differentiation between stimulus categories with the strongest results for trans men and lesbian scenes. Activation of the ventral striatum supported our hypothesis only for lesbian scenes in trans women. This prominent role of lesbian stimuli might be explained by their differential responses in cis women and men. We show that correlates of sexual arousal in transgender individuals might change in direction of the chosen gender. Future investigations longer into transition might resolve the discrepancy on behavioral and neuronal levels.

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Species and Recombination Effects on DNA Variability in the Tomato Genus

Genetics ◽

10.1093/genetics/158.4.1725 ◽

2001 ◽

Vol 158 (4) ◽

pp. 1725-1735 ◽

Cited By ~ 5

Author(s):

Emmanuelle Baudry ◽

Carole Kerdelhué ◽

Hideki Innan ◽

Wolfgang Stephan

Keyword(s):

Mating System ◽

Recombination Rate ◽

Sequence Variation ◽

Single Copy ◽

Recombination Rates ◽

Dna Sequence Variation ◽

Incompatibility Alleles ◽

Selection For ◽

Weak Influence ◽

Selfing Species

Abstract Population genetics theory predicts that strong selection for rare, beneficial mutations or against frequent, deleterious mutations reduces polymorphism at linked neutral (or weakly selected) sites. The reduction of genetic variation is expected to be more severe when recombination rates are lower. In outbreeding species, low recombination rates are usually confined to certain chromosomal regions, such as centromeres and telomeres. In contrast, in predominantly selfing species, the rarity of double heterozygotes leads to a reduced effective recombination rate in the whole genome. We investigated the effects of restricted recombination on DNA polymorphism in these two cases, analyzing five Lycopersicon species with contrasting mating systems: L. chilense, L. hirsutum, L. peruvianum, L. chmielewskii, and L. pimpinellifolium, of which only the first three species have self-incompatibility alleles. In each species, we determined DNA sequence variation of five single-copy genes located in chromosomal regions with either high or low recombination rate. We found that the mating system has a highly significant effect on the level of polymorphism, whereas recombination has only a weak influence. The effect of recombination on levels of polymorphism in Lycopersicon is much weaker than in other well-studied species, including Drosophila. To explain these observations, we discuss a number of hypotheses, invoking selection, recombination, and demographic factors associated with the mating system. We also provide evidence that L. peruvianum, showing a level of polymorphism (almost 3%) that is comparable to the level of divergence in the whole genus, is the ancestral species from which the other species of the genus Lycopersicon have originated relatively recently.

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Gene buddies: Linked balanced polymorphisms reinforce each other even in the absence of epistasis

10.1101/220897 ◽

2017 ◽

Author(s):

Jacob A Tennessen

Keyword(s):

Recombination Rate ◽

Evolutionary Dynamics ◽

Balancing Selection ◽

Natural Populations ◽

Adaptive Variation ◽

Recombination Rates ◽

Future Studies ◽

Close Physical Proximity ◽

Selection For ◽

Independent Effects

The fates of genetic polymorphisms maintained by balancing selection depend on evolutionary dynamics at linked sites. While coevolution across linked, epigenetically-interacting loci has been extensively explored, such supergenes may be relatively rare. However, genes harboring adaptive variation can occur in close physical proximity while generating independent effects on fitness. Here, I present a model in which two linked loci without epistasis are both under balancing selection for unrelated reasons. Using forward-time simulations, I show that recombination rate strongly influences the retention of adaptive polymorphism, especially for intermediate selection coefficients. A locus is more likely to retain adaptive variation if it is closely linked to another locus under balancing selection, even if the two loci have no interaction. Thus, two linked polymorphisms can both be retained indefinitely even when they would both be lost to drift if unlinked. Such clusters of mutually reinforcing genes may underlie phenotypic variation in natural populations. Future studies that measure selection coefficients and recombination rates among closely linked genes will be fruitful for characterizing the extent of this phenomenon.

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Extreme Differences in Recombination Rate between the Genomes of a Solitary and a Social Bee

Molecular Biology and Evolution ◽

10.1093/molbev/msz130 ◽

2019 ◽

Vol 36 (10) ◽

pp. 2277-2291 ◽

Cited By ~ 4

Author(s):

Julia C Jones ◽

Andreas Wallberg ◽

Matthew J Christmas ◽

Karen M Kapheim ◽

Matthew T Webster

Keyword(s):

Recombination Rate ◽

Rate Variation ◽

Sequencing Data ◽

Recombination Rates ◽

Evolution Of Sociality ◽

Leafcutter Bee ◽

Selection For ◽

Worker Caste ◽

Recombination Rate Variation ◽

Genomic Recombination

Abstract Social insect genomes exhibit the highest rates of crossing over observed in plants and animals. The evolutionary causes of these extreme rates are unknown. Insight can be gained by comparing recombination rate variation across the genomes of related social and solitary insects. Here, we compare the genomic recombination landscape of the highly social honey bee, Apis mellifera, with the solitary alfalfa leafcutter bee, Megachile rotundata, by analyzing patterns of linkage disequilibrium in population-scale genome sequencing data. We infer that average recombination rates are extremely elevated in A. mellifera compared with M. rotundata. However, our results indicate that similar factors control the distribution of crossovers in the genomes of both species. Recombination rate is significantly reduced in coding regions in both species, with genes inferred to be germline methylated having particularly low rates. Genes with worker-biased patterns of expression in A. mellifera and their orthologs in M. rotundata have higher than average recombination rates in both species, suggesting that selection for higher diversity in genes involved in worker caste functions in social taxa is not the explanation for these elevated rates. Furthermore, we find no evidence that recombination has modulated the efficacy of selection among genes during bee evolution, which does not support the hypothesis that high recombination rates facilitated positive selection for new functions in social insects. Our results indicate that the evolution of sociality in insects likely entailed selection on modifiers that increased recombination rates genome wide, but that the genomic recombination landscape is determined by the same factors.

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SELECTION ON RECOMBINATION IN CLINES

Genetics ◽

10.1093/genetics/91.3.581 ◽

1979 ◽

Vol 91 (3) ◽

pp. 581-589 ◽

Cited By ~ 1

Author(s):

D Charlesworth ◽

B Charlesworth

Keyword(s):

Recombination Rate ◽

Environmental Changes ◽

Recombination Rates ◽

Selection Pressures ◽

Selection Models ◽

Linear Sets ◽

Selection For ◽

Parameter Values

ABSTRACT Computer runs have been done to examine SLATKIN'S (1975) model for selection on recombination rates in linear sets of populations with environmental changes affecting two loci. In order to determine whether the suggested selection pressures on recombination do, in fact, exist, we follow the changes in frequency at a third locus that is polymorphic for alleles affecting the recombination rate between the two selected loci. With haploid or diploid selection models, there can be selection for increased recombination if the parameter values are chosen suitably, but changes in parameter values often lead to changes in the direction of selection, so that decreased recombination is favored, The selection for increased recombination is usually weak, while that for decreased recombination is frequently much stronger. Weaker selection on the selected loci often leads to increasing selection for decreased recombination.

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