Talk:Dominance and recessivity

Talk

Discussion for: Dominance and recessivity • View • Links • Related changes

Use this page for verification notes, disputes, and action items. Keep narrative content on the article.

Page scope

Dominance and recessivity covers how the two alleles at a locus act together in a heterozygote: complete, partial and no dominance, overdominance and codominance; Mendel's terms; codominant markers; how dominance can differ between characters of one allele; why mutant alleles are often recessive; recessive alleles in outcrossing populations and inbred lines; and dominance in quantitative variation. Its cannabis cases are day-neutral flowering (Autoflower1, Autoflower2), the THC to CBD ratio and the recessive forms of inbred hemp in Soviet and Russian breeding. The characters themselves belong to Genetic traits; the B locus to Chemotype; heterozygosity as a measure of variation to Heterozygosity; inbreeding depression and heterosis to Outcrossing, Inbreeding depression and Heterosis; variance components to Heritability; the heterozygote advantage to Overdominance.

Data verification

Record source conflicts, dating problems and sources not used here. Keep narrative content on the article.

Discussion

Sources

Beavis, Lamkey, Espinosa, Mahama and Suza, "Gene Effects", in Suza and Lamkey (eds), Quantitative Genetics for Plant Breeding (2023): the coded genotypic values +a, d and −a, and the degrees of dominance from none to overdominance.
Abbott and Fairbanks (2016), Genetics 204: 407–422: a new English translation of Mendel's paper on pea hybrids, with his definitions of dominant and recessive characters, the seven pairs of characters in Pisum and the intermediate hybrids of earlier crosses.
de Meijer and colleagues (2003), Genetics 163: 335–346: crosses of pure CBD and pure THC plants, the mixed F1, the 1:2:1 F2, the codominant alleles B_D and B_T and a codominant marker linked to chemotype.
Wenger and colleagues (2020), American Journal of Botany 107: 1423–1432: functional and non-functional alleles of CBDA synthase, the three chemotype classes in feral plants and a test cross.
Grassa and colleagues (2021), New Phytologist 230: 1665–1679: close physical linkage of the CBDA and THCA synthase loci as the cause of their single-locus inheritance.
Toth, Stack, Carlson and Smart (2022), Frontiers in Plant Science 13: 991680: Autoflower1, its recessive segregation under long days, the intermediate field performance of heterozygotes, the complementation test with Picolo and heterozygous cultivars on the market.
Dowling and colleagues (2024), The Plant Journal 119: 383–403: Autoflower2 in FINOLA and Picolo, the candidate gene CsFT1, its dominance and the cross of Le Crème with Picolo.
Felsenstein, Theoretical Evolutionary Genetics (text of December 2019), pp. 80, 85, 165, 242–244, 385, 423–425, 429–430 and 434–435: selection on rare recessive alleles; overdominance and heterosis; Fisher's theory of dominance and the replies of Wright, Haldane and Muller; Charlesworth's review; recessive deleterious alleles and inbreeding; additive and dominance variance; heritability and the response to selection.
Davinack, Molecular Ecology & Evolution: An Introduction (2024), pp. 29–30 and 153–154: loss-of-function, gain-of-function and dominant-negative mutations; codominant markers.
Serkov and Klimova (2016), Niva Povolzh'ya 2 (39): 52–60 (in Russian): self-pollinated lines of monoecious hemp, with a review of earlier Soviet work (Kaplunova, Gorshkova) on recessive characters in inbred hemp.

Terms

Codominance and incomplete dominance are both used of the THC to CBD ratio. De Meijer and colleagues call the B_D and B_T alleles codominant; Wenger and colleagues test "codominant Mendelian inheritance" and in the same paper speak of "incomplete dominance affecting the THC:CBD ratio". Both mean here that heterozygotes are intermediate.
Day-neutral, photoperiod-insensitive and autoflowering name the same habit: flowering whatever the day length.
FINOLA is written in capitals as Dowling and colleagues write it.

Source discrepancies

Absence of THC as a recessive character. Serkov and Klimova state that the absence of THC is recessive in hemp, and Gorshkova's inbred progenies selected against cannabinoids rose to a recessive-allele frequency of 0.994. The chemotype studies of de Meijer and colleagues and of Wenger and colleagues find the THC to CBD ratio intermediate in heterozygotes. The two concern different characters: total cannabinoid absence in the Russian work, the ratio of two cannabinoids in the others.
Gorshkova's 17th generation. In Serkov and Klimova's account of Gorshkova's 17th generation, the share of plants without CBD, THC and CBN is printed as "93.96", with no unit.
Heterozygotes for Autoflower1 in the field. Toth and colleagues write that heterozygotes flowered about two weeks earlier "than plants that were homozygous for Autoflower1", while their figure shows heterozygotes intermediate between the two homozygotes. The sentence does not name the homozygote meant.

Images reserved in the article

One image has a place in the article but is not yet uploaded:

File:Cannabis-dominance-genotypic-value-scale.jpg (The heterozygote between its parents), a diagram to be drawn: a number line with aa at −a, AA at +a and 0 at the midpoint, and five markers for the heterozygote Aa at 0 (no dominance), between 0 and +a (partial dominance of A), at +a (complete dominance), beyond +a (overdominance) and between 0 and −a (partial dominance of a). No traits, crops or numbers.