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•The contents of the nucleus are enclosed by the ___________.
•A typical nondividing nucleus includes:
–Chromosomes as extended fibers of _____________.
–__________ for rRNA synthesis.
–Nucleoplasm as the fluid where solutes are dissolved.
–The __________, which is the protein-containing fibrillar network.
- •nuclear envelope
- -nuclear matrix
•The Nuclear Envelope
–Divides the nucleus from its _________
–Consists of two membranes separated by a nuclear space
•The two membranes are fused at sites forming a _______
–The inner surface of the nuclear envelope is lined by the ___________.
- •nuclear pore
- -nuclear lamina
•The nuclear lamina
–Supports the ________.
–Composed of ________.
–The ________ is regulated by phosphorylation and dephosphorylation.
- -nuclear envelope
–Proteins and RNA are transported in and out of the nucleus via _________.
–Nuclear pores contain the ___________ that appears to fill the pore like a stopper.
–NPC is composed of ~30 proteins called ___________.
- -nuclear pores
- -nuclear pore complex (NPC)
•Nuclear Pore Complex
–Proteins synthesized in the cytoplasm are targeted for the nucleus by the ______.
–Proteins with a NLS stretch bind to an __________.
–Conformation of the NPC changes as the protein passes through.
–RNAs move through the NPCs as RNPs and carry ____________ to pass through.
- -nuclear localization signal (NLS)
- -NLS receptor (importin)
- -NES (nuclear export signals)
–The protein component of chromosomes include _________.
•High content of basic amino acids
–DNA and histones are organized into repeating subunits called _________.
–Each nucleosome includes a core particle of supercoiled DNA and histone H1 serving as a linker.
–DNA is wrapped around the core complex.
•Consists of two molecules each of H2A, H2B, H3, and H4 forming an octamer.
•Heterochromatin and Euchromatin
–Euchromatin returns to a dispersed state after mitosis.
–Heterochromatin is condensed during interphase.
•___________ heterochromatin remains condensed all the time.
•__________ heterochromatin is inactivated during certain phases of the organism’s life.
–The end of each chromosome is called a telomere and is distinguished by a set of repeated sequences.
–New repeats are added by a ___________, a reverse transcriptase that synthesizes DNA from a DNA template.
–Telomeres are required for the complete replication of the chromosome because they protect the ends from being degraded.
–Telomerase activity is thought to have major effects on cell life.
•_________–At the site markedly indented on a chromosome
–Contain _________ heterochromatin
–Site of microtubule attachment during mitosis.
–DNA sequence is not important for centromere structure and function.
–____________ depends on factors other than DNA sequences.
–Parental histones determine the chemical modifications found in the newly synthesized histones.
–The ___________ is a network of protein-containing fibrils.
–It serves as more than a ______ to maintain the shape of the nucleus and anchoring the machinery involved in nuclear activities.
•_________ involve the breakage of a chromosome and resealing of the segment in a reverse order.
•__________ are the result of the attachment of all or one piece of one chromosome to another chromosome.
•___________ result when thee is loss of a portion of a chromosome.
•_________ occur when a portion of a chromosome is repeated.