Biosystematic studies in the Stylidium crassifolium species complex (Stylidiaceae)

1979 ◽  
Vol 27 (1) ◽  
pp. 27 ◽  
Author(s):  
BJ Banyard ◽  
SH James
Keyword(s):  
Species Complex ◽  
Genetic System ◽  
Lethal Gene ◽  
Great Efficiency ◽  
Intermediate Species ◽  
Gene Arrays ◽  
Recessive Lethal ◽  
Tetraploid Form ◽  
Diploid Populations ◽  
Lethal Genes

Stylidium elongatum Benth. (n = 13, 26) and Stylidium crassifolium R. Br. (n = 14, 28) have been restored to specific status and a morphologically intermediate species, Stylidium confluens sp. nov. (n = 14), is described. Polyploid entities in the complex have not been given taxonomic ranks although the tetraploid form of elongatum may be considered worthy of subspecific rank, as it is ecologically distinct and contiguously allopatric to its progenitor and to confluens, forming a buffer between these two diploid entities. Tetraploid populations in crassifolium occur within the distributional range of the diploid. All three species carry recessive lethal gene arrays which eliminate the products of self-pollination with great efficiency and result in crosses between close populations yielding seed more effectively than crosses within populations. There is evidence that interpopulational coadaptation may break down with increasing distance between populations. Polyploidy in crassifolium is probably a conservative response in the genetic system of a species where concentrations of lethal genes in small diploid populations became disadvantageous.

scholarly journals Colonization of the Americas by Drosophila subobscura: lethal-gene allelism and association with chromosomal arrangements.

Genetics ◽  
1995 ◽  
Vol 140 (4) ◽  
pp. 1297-1305
Author(s):  
F Mestres ◽  
L Serra ◽  
F J Ayala
Keyword(s):  
Drosophila Subobscura ◽  
Rapid Expansion ◽  
Lethal Gene ◽  
Latitudinal Cline ◽  
Recessive Lethal ◽  
Central California ◽  
High Incidence ◽  
Palearctic Species ◽  
Lethal Allelism ◽  
Lethal Genes

Abstract Drosophila subobscura is a Palearctic species that has recently colonized the Americas. It was first found in 1978 in Puerto Montt, Chile, and in 1982 in Port Townsend, WA. The colonization and rapid expansion of the species in western South and North America provides distinctive opportunities for investigating the process of evolution in action. The inversion polymorphism in the O chromosome from populations of central California and northern Washington, separated by 1300 km, corresponds to a previously observed latitudinal cline, also observed in Europe. Recessive lethal genes are not randomly distributed among the chromosomal arrangements. The incidence of lethal allelism is high, yielding unrealistically low estimates of the effective size of these populations (on the order of 1000 individuals). The high incidence of lethal allelism is likely to be a consequence of the low number of the American colonizers (on the order of 10-100 individuals), but the persistence of the allelism over several years suggests that some lethal-carrying chromosomes may be heterotic owing to shared associations between lethal and other genes.

scholarly journals Why Recessive Lethal Alleles Have Not Disappeared?

2021 ◽  
pp. 69-80
Author(s):  
Jorma Jormakka ◽  
Sourangshu Ghosh
Keyword(s):  
Ethnic Groups ◽  
Lethal Gene ◽  
Recessive Lethal ◽  
Lethal Genes

The article derives the probability for lethal recessive alleles in the case of recessive disadvantage or advantage. It is shown that recessive advantage of a lethal gene can be detected by the ratio of heterozygotes and homozygotes. This demonstrates that higher IQ of certain ethnic groups cannot be explained by recessive advantage of lethal genes. The article shows that lethal genes can survive in the population if some lineages of families have much more children than the average.

scholarly journals Why Recessive Lethal Alleles Have Not Disappeared?

2021 ◽  
Author(s):  
Jorma Jormakka ◽  
Sourangshu Ghosh
Keyword(s):  
Ethnic Groups ◽  
Lethal Gene ◽  
Recessive Lethal ◽  
Lethal Genes

The article derives the probability for lethal recessive alleles in the case of recessive disadvantage or advantage. It is shown that the recessive advantage of a lethal gene can be detected by the ratio of heterozygotes and homozygotes. This demonstrates that the higher IQ of certain ethnic groups cannot be explained by the recessive advantage of lethal genes. The article shows that lethal genes can survive in the population if some lineages of families have much more children than the average.

The role of the genome in the development of the haploid syndrome in Anura

Development ◽  
1966 ◽  
Vol 16 (3) ◽  
pp. 559-568
Author(s):  
Louie Hamilton
Keyword(s):  
Good Evidence ◽  
Contributory Factor ◽  
Diploid Nucleus ◽  
Haploid Nucleus ◽  
Recessive Lethal ◽  
Partial Failure ◽  
Lethal Genes

The problem of the factors involved in the development of the haploid syndrome in anuran embryos is as yet unsolved. It is known that about 90 % of all haploid frog embryos develop the haploid syndrome, which is characterized by the presence of oedema and sluggishness, by reduction in pigmentation and in the efficiency of the heart and circulation, and by a partial failure of the gut to coil and of muscle to differentiate. The two most favoured explanations of the development of the haploid syndrome have been nucleocytoplasmic imbalance, since a haploid nucleus is only half the size of a diploid nucleus in the same-sized egg, and unmasked recessive lethal genes. There is good evidence that an abnormal nucleocytoplasmic ratio is an important contributory factor in the development of the haploid syndrome. Briggs (1949) compared populations of haploids developing from large and small eggs and Subtelny (1958) compared the development of haploids and homozygous diploids which possessed a reduplicated set of haploid chromosomes.

scholarly journals Low diversity of t haplotypes in the eastern form of the house mouse, Mus musculus L.

Genetics ◽  
1991 ◽  
Vol 127 (1) ◽  
pp. 161-168
Author(s):  
A Ruvinsky ◽  
A Polyakov ◽  
A Agulnik ◽  
H Tichy ◽  
F Figueroa ◽  
...  
Keyword(s):  
Soviet Union ◽  
House Mouse ◽  
Mus Musculus ◽  
Complementation Test ◽  
Antigenic Determinants ◽  
Lethal Gene ◽  
Eastern Siberia ◽  
Wild Mice ◽  
Low Diversity ◽  
Lethal Genes

Abstract In previous studies, 13 different recessive embryonic lethal genes have been associated with t haplotypes in the wild mice of the species Mus domesticus. In this communication we have analyzed five populations of Mus musculus for the presence and identity of t haplotypes. The populations occupy geographically distant regions in the Soviet Union: Altai Mountains, western and eastern Siberia, Azerbaijan and Turkmenistan. No t haplotypes were found in mice from eastern Siberia. In the remaining four populations, t haplotypes occurred with frequencies ranging from 0.07 to 0.21. All the t haplotypes extracted from these populations and analyzed by the genetic complementation test were shown to carry the same lethal gene tcl-w73. In one population (that of western Siberia), another lethal gene (tcl-w5) was found to be present on the same chromosome as tcl-w73. This situation is in striking contrast to that found in the populations of the western form of the house mouse, M. domesticus. In the latter species, tcl-w73 has not been found at all and the different populations are characterized by the presence of several different lethal genes. The low diversity of t haplotypes in M. musculus is consistent with lower genetic variability of other traits and indicates a different origin and speciation mode compared to M. domesticus. Serological typing for H-2 antigenic determinants suggests that most, if not all, of the newly described t haplotypes might have arisen by recombination of tw73 from M. musculus with t haplotypes from M. domesticus either in the hybrid zone between the two species or in regions where the two species mixed accidentally.

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