07BIS1012013ReplicLect_7

For dna replication ts mutants fall into two

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Unformatted text preview: referred way to Conditional genetically study cellular functions that are absolutely critical for cell viability. for BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 37 Conditional Lethal Mutants ­ ­ ­ Conditional lethal mutations affect critical cellular functions such as Conditional replication, transcription and translation. Conditional lethal mutants exhibit their phenotypes only under Conditional “restrictive” or “non-permissive” conditions. conditions. For example, under permissive conditions (e.g., low temperature) cells grow and replicate DNA normally. However, under restrictive or non-permissive conditions (e.g., high temperature) cells stop replicating DNA and die. A common type of conditional lethal is the temperature sensitive (ts) common mutant. For DNA replication ts mutants fall into two categories: ts q q Mutants that complete ongoing rounds of replication and then stop Mutants and fail to initiate new rounds of replication ( slow stop). These and ). mutants are also called initiation mutants. initiation The second class of mutant is the "instant stop" type in which DNA The replication stops immediately upon shifting to the restrictive temperature. Instant stop mutants typically involve those components of the replication fork required for DNA synthesis. BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 38 Genes Involved in E. Coli DNA Replication Genes E. Gene Gene Product and/or Function Map Location dnaJ DNA Replication 0.5 min. dnaK DNA Replication 0.5 min. polB DNA polymerase II 2 min. polC/dnaE Alpha subunit of DNA polymerase III 4 min. dnaL DNA replication 28 min. ter Terminus of chromosomal replication 27-43 min. dnaI Initiation of Chromosomal replication 39 min. lig DNA ligase gap sealing, Okazaki fragment joining 51 min. rpoD RNA polymerase sigma subunit 66 min. dnaG Primase-makes primer for extension of DNA polymerase 66 min. rpoA DNA polymerase, alpha subunit 72 min. dnaA Initiation of DNA replication 82 min. ori Origin of chromosomal replication 83 min. rep Helicase, unwinding activity to generate single-stranded DNA 83 min. dnaP Initiation of chromosomal replication 84 min. polA DNA polymerase I 85 min. rpoB RNA polymerase beta subunit 89 min. rpo C RNA polymerase beta’ subunit 89 min. dna B DNA replication 91 min. ssb Single-stranded binding proteins 91 min. dnaC Initiation of chromosomal replication, helicase 99 min. BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 39 Requirements & Components for DNA Replication Rules: 1. DNA (and R...
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