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LS3 - Micro Bio (L4)
Lecture 4
| Question | Answer |
|---|---|
| some molecules are circular (covalently closed) | most Eubacterial chromosomes Mitochondria, chloroplasts Episomes (plasmids) some bacteriophage & viruses |
| some molecules are linear | most eukaryotic chromosomes Some bacteriophage & viruses |
| Most DNA in Eubacteria is ____, because has to be organized due to small space. | supercoiled |
| Bacterial chromosome is folded into the | nucleoid |
| Enzyme that allows DNA to change between relaxed and supercoiled structure. Results in a decreased number of base pairs. Keep DNA in cell in manageable forms. | topoisomerase |
| DNA in the cell is _____ supercoiled, also known as right handed coiling. | negatively |
| number of helical turns @ 10(.5) bp per turn. | Twist |
| number of times that double helix crosses over itself | Writhe |
| Twist + Writhe | Linking number |
| Creates a single-strand break, changes linking number by 1. Acts through a covalent intermediate. | Topoisomerase 1 |
| Creates double-strand break, changes linking number by 2. Requires ATP. | Topoisomerase 2 |
| DNA/protein complex. Compacts DNA. Protects DNA from damage. Facilitates segregation into daughter cells. | Chromatin |
| The processes chromatin inhibits that require unwinding of DNA | transcription, replication, recombination |
| proteins can induce ___ | supercoiling |
| nucleosomes induce ___ supercoil | negative |
| the enzyme responsible for cleavage of chromosomes | Micrococcal nuclease |
| Each histone has a core region that folds into a “_____” and a flexible _____ tail | histone fold, N-terminal |
| H2A and H2B form a | dimer |
| H3 and H4 form a | tetramer |
| The nucleosome is assembled by binding DNA to | H3-H4 tetramer |
| two __-___ dimers must be binded first, prior to nucleosome assembly | H2A-H2B |
| Consist of 8 core Histone proteins. Cover 146 bp of DNA + 1 Linker Histone (H1). Covers ~180-bp DNA. | Nucleosomes |
| 10nm Fibers coil into __ nm Fibers | 30 |
| 30 nm Fibers fold into 200 nm DNA loop domains describes the structure of | chromosomes |
| 700 nm chromatid = ____ kb | 100,000 |
| 200 nm loops = ___ kb | 50-100 |
| 200 nm Loop Domains resemble _____. Similar structures found in bacteria. | circular DNA |
| In the Electron micrograph of eukaryotic cell showing chromatin organization, heterochromatin is | dense |
| In the Electron micrograph of eukaryotic cell showing chromatin organization, euchromatin is | loose |
| local melting necessary for ___, ___, and ___ | replication, transcription, recombination |
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