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mole. genetics ch. 7
chromosomes
| Question | Answer |
|---|---|
| why does DNA need to condense? | because it needs to be able to fit not only in the cell, but in the nucleus that way all cellular processes can be accomplished in this space. |
| How are RNA viruses assembled? | the capsid is assembled around the RNA genome that starts at the nucleation center and proceeds bidirectionally until the ends are reached, causing the RNA to become coiled in a helical array on the inside of the protein shell. |
| how are DNA viruses assembled? | The spherical capsids of DNA viruses are assembled as an empty headshell from a small set of proteins, The duplex genome then is inserted into the head, accompanied by a structural change in the capsid. |
| How is the genome packed in each type of virus? | the loops that the genome produces are secured by an unknown mechanism and are condensed by proteins |
| what is terminase? | a specialized protein motor complex essential for packing double-stranded DNA (dsDNA) into the capsid of bacteriophages and some eukaryotic viruses |
| what are NAPs? | they are nucleoid-associated proteins that are involved in bacteria DNA folding |
| what is a nucleoid? | a non-membrane bound region in prokaryotic cells and is divided into many chromosomal domains, appearing as interwound supercoiled loops emanating from a dense core. |
| how is a nucleoid organized? | it is organized through negative supercoiling, plectonemic loops, and compaction by nucleoid-associated proteins (NAPs) |
| how is eukaryotic DNA organized? | DNA is attached to the nuclear matrix at specific sequences called MARs (matrix attachment regions) |
| what are MARs? | matrix attachment regions that DNA binds to, and it is A-T rich (~70%) but does not have any specific consensus sequence. |
| what is chromatin? | mixture of DNA and proteins that form the chromosomes found in the cells of humans and other higher organisms. |
| what is euchromatin? | DNA that is much less densely packed than in the mitotic chromosomes. |
| what is heterochromatin? | DNA that remains densely packed throughout interphase |
| what are G bands? | chromosomes that are subject to trypsin generate distinct chromosome specific patterns. |
| how are G bands created? | when they are stained with the chemical dye Geimsa |
| how do the bands differ from one another? | they can include hundreds of different genes and can have different baser pair content. |
| what is a lampbrush chromosome? | an unusually elongated chromosome form that are found in the oocytes of specific amphibians and birds. They are about 30 times less compacted than at mitosis and are covered with extruded loops of chromatin that are sites of active transcription. |
| what is a polytene chromosome? | chromosomes that are generated by successive replications of a chromosome set without separation of the replicas. They come from the salivary gland of Drosophila melanogaster |
| what can be studied with lampbrush and polytene chromosomes? | chromosome structure and the structural changes associated with transcription can be studied with these type of chromosomes. |
| what is a puff? | a localized, swollen region of a polytene chromosome where the DNA has decondensed, indicating high-level gene expression (transcription) |
| how does the eukaryotic chromosome separate during mitosis? | during anaphase, the sister chromatids move to opposite poles of the cell |
| what are microtubules? | cylindrical rods that attach to the outer ends of the poles of the cell, and also form the mitotic spindle |
| what are spindles? | fibers that hold the chromosome and also separate it during mitosis |
| what are MTOCs? | A region from which microtubules form/come out of. |
| what are centromeres? | A constricted region of a chromosome that includes the site of attachment (the kinetochore) to the mitotic or meiotic spindle |
| what are kinetochores? | complex, disc-shaped protein structure assembled on the centromeric region of chromosomes that acts as the primary attachment point for spindle microtubules during mitosis and meiosis |
| what are telomeres and what is their makeup? | telomeres are the natural end of chromosomes, and they are made up of noncoding, repeating DNA sequences. |
| what is telomerase and what does it do? | an enzyme that restores short bits of DNA in telomeres which are otherwise shortened after repeated mitosis. they allows each offspring to replace the lost bit of DNA, allowing the cell line to divide without ever reaching the limit |
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angievelasco
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