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Trypanosoma brucei: Inheritance of Kinetoplast DNA Maxicircles in a Genetic Cross and Their Segregation during Vegetative Growth

https://doi.org/10.1006/expr.1995.1029Get rights and content

Abstract

The inheritance of maxicircle DNA was determined using a polymorphic EcoRI restriction site in the maxicircle variable region. In 11 hybrid progeny from a genetic cross of two stocks of Trypanosoma brucei, 7 progeny apparently inherited maxicircles uniparentally from either parent, in agreement with the results from previous studies, but in 4 progeny inheritance was biparental. Three subclones from 2 of these 4 progeny were made,and in these the maxicircles of only one parental type were detected. These data are considered in terms of a simple model whereby half the maxicircle genomes are inherited from each parent into progeny at meiosis with subsequent stochastic segregation at each mitotic division. This model generates a quantitative prediction as to the period of time required for fixation of inheritance to a uniparental pattern which provides a reasonable fit to the experimental data. These results provide an explanation as to why previous studies have shown that maxicircles are (apparently) inherited uniparentally: the kinetoplast is a unitary organelle inherited faithfully at cell division, but the maxicircles that it contains are best considered as a population that divides stochastically. Consideration of the model also explains why maxicircle populations are homogeneous.

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