Larva Chromosome

Figure 36-4. Illustration of the tight correlation between the presence of RNA polymerase II and RNA synthesis. A number of genes are activated when Chirono-mus tentans larvae are subjected to heat shock (39 °C for 30 minutes). A Distribution of RNA polymerase II (also called type B) in isolated chromosome IV from the salivary gland (at arrows). The enzyme was detected by immunofluorescence using an antibody directed against the polymerase. The 5C and BR3 are specific bands of chromosome IV, and the arrows indicate puffs. B Autoradiogram of a chromosome IV that was incubated in H-uridine to label the RNA. Note the correspondence of the immunofluorescence and presence of the radioactive RNA (black dots). Bar = 7 pm. (Reproduced, with permission, from Sass H RNA polymerase B in polytene chromosomes. Cell 1982 28 274. Copyright 1982 by the Massachusetts Institute of Technology.)...

Aziz, J.B., N.M. Akrawi, and G.A. Nassori. 1991. The effect of chronic toxicity of copper on the activity of Balbiani rings and nucleolar organizing region in the salivary gland chromosomes of Chironomus ninevah larvae. Environ. Pollut. 69 125-130. 

CHL, Chromosomal aberrations, human lymphocytes in vitro HMM, Host-mediated assay in NMRI mice MST, Spot test, C57BL/6JHan x T mice MVA, Micronucleus test, amphibian Caudiverbera caudiverbera larvae in vivo (+) NT 90 75 sc X 1 50 ip X 1 1.5 ug/nil. Ziemsenefa/. (1987) Busehnaier et al. (1972) Fahrig etal. (1978) Venegas etal. (1993)... 

Ecdysone stimulates the synthesis of RNA in tissues. Visual demonstration of the effect is provided by its action on polytene chromosomes of fly larvae (Fig. 26-14).361 Fifteen minutes after the application of ecdysone, a puff is induced on one band of the chromosome a second puff forms at a later time while a preexisting puff diminishes. Thus, like steroid hormones in mammals, ecdysone appears to have a direct controlling effect on transcription. The cuticle-shedding process (ecdysis) is initiated by the brain peptide eclosian. However, the brain may be responding to the ecdysis-triggeiing hormone, a peptide that is secreted by a series of epitracheal glands located in various segments of the body.362... 

Fig. 5.3 Correlation between nitrile formation and herbivory by Trichoplusia ni in 96 A. thaliana Col-0 x her recombinant inbred lines, (a) The major quantitative trait loci controlling nitrile formation and T. ni herbivory on chromosome I are virtually identical, (b) Larvae of T. ni feed more on lines that produce nitriles than lines that produce isothiocyanates (n = 56, ro = 0.273, p < 0.001).

In the same way that amphibian oocytes are an accessible scource of giant lampbrush chromosomes (as well as nuclear envelopes), the salivary glands of dipteran larvae are a source of giant polytene chromosomes, which are formed by repeated endomitotic reduplication of the DNA, while retaining lateral association of chromatids. In Chironomus tentans, polytene chromosomes in salivary... 

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