Drubin Lecture 25 - Drubin - Lecture 25: Nuclear and...

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Drubin - Lecture 25: Nuclear and Chromatin Structure MCB 130 The Nucleus and Chromatin Structure 1 . Overall nuclear organization: Separation of nucleoplasm from cytoplasm in eukaryotes allows spatially separate processing of transcripts in nucleus before they are exported for protein synthesis (Figure 1). a) nuclear envelope (NE) – connected to ER; A double membrane system b) nuclear pores – route of mRNA transport. Nuclear pores provide passages through both membranes (figure 1). c) chromatin: DNA molecules are packaged with histones and nonhistone proteins as chromatin. (DNA 1/3 mass, histones 1/3, nonhistone chromosomal proteins 1/3) heterochromatin – more condensed, transcriptionally inactive, contains many middle repetitive and highly repetitive sequences, found near the nuclear envelope, is usually late replicating euchromatin – less condensed, actively transcribed genes, found in nuclear interior 2. The nucleus has specialized functional domains: a) nucleolus: site of ribosomal RNA synthesis The nucleolus is organized by a special domain on one of the chromosomes that contains rRNA genes (Nucleolar Organizer Region). It consists of a fibrillar central matrix, i.e. DNA, dense fibrillar cores, and a granular zone where ribosomal precursors are being assembled. b) chromosomal patches:
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This note was uploaded on 04/02/2008 for the course MCB 130 taught by Professor Schekman during the Spring '08 term at University of California, Berkeley.

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Drubin Lecture 25 - Drubin - Lecture 25: Nuclear and...

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