Abstract
Publisher Summary This chapter provides an overview of lampbrush chromosomes. Amphibian oocytes, like most animal oocytes, undergo their entire growth period during prophase of the first meiotic division. The earliest meiotic stages—leptotene, zygotene, pachytene, and early diplotene—occur before any significant enlargement. The chromosomes then “arrest” in diplotene while the nucleus and the cell undergo dramatic growth. Just when the lampbrush stage is reached is a matter of definition. Transcriptionally active chromosomes are present from the beginning of the growth phase, and in this sense lampbrush chromosomes are present throughout oogenesis. In frogs and salamanders from temperate climates, the condition of the chromosomes depends strongly on the season, which, of course, governs the hormonal state of the animal. Thus, lampbrush chromosomes from the largest oocytes of the newt N. Viridescens have extended loops in the fall and winter, but just before egg laying in spring, the loops regress as the chromosomes condense. The chapter describes protocol for lampbrush chromosomes of Xenopus .
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