Classic Layout

Organization of Nuclear DNA in Eukaryotes

Each eukaryotic nucleus encloses a fixed number of chromosomes which contain the nuclear DNA. During most of a cell’s life, its chromosomes exist in a highly extended linear form. Prior to cell division, however, they condense into much more compact bodies which can be examined microscopically after staining. The duplication …

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Genome Structure in Viruses & Prokaryotes

The genomes of viruses and prokaryotes are very simple structures, although those of viruses show remarkable diversity (for a review see Dimmock et al. 2001). Most viruses have a single linear or circular genome but a few, such as reoviruses, bacteriophage φ6 and some plant viruses, have segmented RNA genomes. …

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DNA Reassociation Kinetics & Sequence Complexity

When double-stranded DNA in solution is heated, it denatures (‘melts’) releasing the complementary single strands. If the solution is cooled quickly the DNA remains in a single-stranded state. However, if the solution is cooled slowly reassociation/reannealing i. e. spontaneous realignment of two single DNA strands to re-form a DNA double …

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Salt mines

Salinity: Sources, Cycles & Classification

Over four-fifths of the surface of our planet is covered with a salt solution (oceans & seas) containing, among many other constituents, approximately 0.5M NaCl. Still, only very few groups of higher plants can withstand such conditions. Most terrestrial species are unable to tolerate even one-tenth of the salt concentration …

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পৃথিবীর ভবিষ্যত: মরুভূমি নাকি অরণ্য?

পৃথিবীর দক্ষিণ গোলার্ধের দিকে অবস্থিত একটি প্রাচীন হ্রদ খুঁজে পান বিজ্ঞানীরা। পূর্বে এখানে পানি থাকলেও কালের পরিক্রমায় তা এখন ভরাট। তবে তা মানুষ ভরাট করে নি, প্রাকৃতিকভাবেই হয়েছে। এ হ্রদ ভরাট হবার সময় মাটি চাপা পড়ে সেসময়কার গাছের পাতা, কীটপতঙ্গ, মাছ। আর এভাবেই সেখানে তৈরি হয় বিভিন্ন জীবের ফসিল। বিজ্ঞানীরা …

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