VARIATION OF SPONTANEOUS OCCURRENCE RATES OF CHROMOSOMAL ABERRATIONS IN THE SECOND CHROMOSOMES OF DROSOPHILA MELANOGASTER

Abstract

After accumulating mutations by the aid of marked inversions, spontaneous occurrence rates of chromosome aberrations were estimated for 1148 chromosome lines that originated from five stem line second chromosomes of Drosophila melanogaster. In chromosome lines originating from three stem chromosomes (CH, PQ, and RT), mutations were accumulated for 7550, 7252, and 7256 chromosome generations, respectively, but no structural change was detected. For the chromosome lines that originated from the other two stem chromosomes, the situation was different: Twenty aberrations (19 paracentric inversions and 1 translocation between the second and the third chromosomes) during 45990 chromosome generations took place in the 500 chromosome lines derived from stem line chromosome (AW), and 92 aberrations (83 paracentric inversions, 6 pericentric inversions, 2 translocations between the second and the third chromosomes and 1 transposition) arose during 45006 chromosome generations in the 500 chromosome lines derived from stem line chromosome (JH). For the AW group the occurrence rate becomes 0.00043 per chromosome per generation for all aberrations and 0.00041 for inversions. For the JH group the corresponding rates are 0.00204 and 0.00198, respectively.—A non-random distribution of the breakpoint on the salivary gland chromosome was observed and the breakpoints were concentrated in the regions 26, 29, 33, and 34.—The cytoplasms and the chromosomes (other than the second chromosomes) were made approximately uniform throughout the experiments. Thus, this remarkable variability in the occurrence rate is most probably due to the differences in one or more chromosomal elements on the original five stem chromosomes. The mutable chromosomes (AW and JH) appear to carry a kind of mutator factor such as hi (Ives 1950).

Restriction map and α-amylase activity variation amongDrosophilamutation accumulation lines

“…However, two facts are worth mentioning. First, this occurred in one of the JH lines for which a higher rate of chromosomal abberation (mostly inversion) was observed (Yamaguchi & Mukai, 1974). Hence, the insertion might reflect the stronger dysgenic property of JH lines.…”

“…However, tests of these lines later indicate that they are all of the M type of the P-M system (Mukai, Harada & Yoshimaru, 1984). A recent in situ hybridization experiment on these lines shows that these lines do not have P elements but have I and hobo elements and that hobo elements are responsible for the chromosome abberations observed by Yamaguchi & Mukai (1974) (Harada, Yukuhiro & Mukai, unpublished results).…”

“…Although the original purpose of this experiment was to measure mutation rates of enzyme coding genes (see also Voelker, Schaffer & Mukai, 1980), other traits were also examined, i.e. chromosomal aberations (Yamaguchi & Mukai, 1974), visible mutations and mutator factors (Scobie & Schaffer, 1982 a) and ADH activities (Mukai, Harada & Yoshimaru, 1984). Genetic variation considered to have arisen during the accumulation periods (150-300 generations) was found for all traits.…”

“…Since mutator activities were suspected to exist among these lines, due probably to dysgenic crosses in the early generations (Yamaguchi & Mukai, 1974;Scobie & Schaffer, 1982 a, b), it was speculated that this new variation might be caused by insertions or deletions of some transposable elements into the coding region or the regions close to the coding region. No relationship between the presence of large insertions and a-amylase activity was apparent among chromosomes sampled from natural populations (Langley et al 1988).…”

Unboxing mutations: Connecting mutation types with evolutionary consequences

“…(b) Overview of mutation types and their mutation rates. Mutation rates are per genome per generation, come from a wide range of taxa, and are taken from Beckmann et al (2007), Brumfield et al (2003), Ducos et al (2007), Farlow et al (2015), Feusier et al (2019), Fu et al (2010), Gemayel et al (2010), Goerner‐Potvin and Bourque (2018), Jarne and Lagoda (1996), Katju and Bergthorsson (2013), Maeda et al (1991), Marriage et al (2009), Marshall et al (2008), Ossowski et al (2010), Ramu et al (2013), Rocchi et al (2012), Schrider et al (2013), Sung et al (2016), Thuillet et al (2002), Vendrell‐Mir et al (2019), Weng et al (2019) and Yamaguchi and Mukai (1974). Please note that this is not an exhaustive overview and that actual ranges are probably larger.…”