Micro Lecture Exam 3

• What is the length, number of genes/base pairs, and doubling time of E. coli?

  -Length: 1,500x longer than cell

  -Genes: 4,200

  -Base pairs: 4.6million (mbp)

  -doubling time: 20 minutes
• Most microbial genomes consist of:

  one chromosome; multiple chromosomes in some organisms
• 2 aspects of a prokaryotic genome?

  -Single, circular chromosome (most common)

  -may have one or more plasmids
• What is the largest bacterial genome? How many bp?

  Sorangium cellulosum, 14.8 Mbp; 11,000+ genes
• What is the smallest bacterial genome?

  Trembloya princeps (139kb; 120 genes)
• How many base pairs are in the human genome?

  3.2 billion
• What are the two DNA categories?

  -NON-coding DNA (more than 90% of eukaryotic genomes, less than 15% prokaryotic genomes)

  -coding DNA
• What is vertical transmission?

  Transmission of a disease or infection from parent to offspring.
• What is Horizontal transmission?

  Spread of a pathogen between individuals in a population
• Where are structural genes and DNA control sequences contained?

  genetic material
• Where can a structural gene exist?

  independently of other genes or contained within operon
• What is an operon?

  A functional DNA unit of multiple genes that are controlled by one promoter and operator
• What is a regulon?

  functional genomic unit with discontinuous set of genes regulated by one regulatory protein
• What is a nucleoid? What components are stored here?

  -prokaryotic cell-where the genetic material is located

  -circular, compact DNA copies with RNA and some Proteins
• What is a domain in reference to packaging DNA?

  supercoiled DNA components
• What is Supercoiling? What do positive/negative mean?

  Overwinding (positive) or underwinding (negative) of DNA strands
• How many base pairs are in one turn of RELAXED DNA?

  10.5 base pairs
• DNA is maintained in supercoiled state


  True
• What type of organisms are positively supercoiled?

  Thermophilic archaea
• What type of organisms are negatively supercoiled?

  most, except thermophilic archaea
• What inserts or removes supercoils?

  cellular enzymes
• What is the function of a Class 1 Topoisomerases?

  introduce single-stranded breaks that may add or remove supercoils (requires ATP)
• What is the function of a Class 2 Topoisomerases?

  introduces double-stranded breaks that insert negative supercoils
• What is the importance of DNA gyrase?

  antibiotic target
• What is semiconservative replication?

  DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand
• What is bidirectional replication?

  DNA replication where two replication forks move in opposite directions from same point of origin
• What is a termination sequence?

  A termination sequence is a specific sequence of characters or symbols that marks the end of a cellular process
• Can a partially replicated chromosome begin a new round of replication before the previous round finishes?

  yes
• What is the origin of replication? What is it recognized by? Blocked by?

  -conserved 250bp sequence

  -DnaA

  -Seq A
• What does binding of origin proteins result in?


  an opening of the DNA helix necessary for replication to begin
• What does Hemi-methalated mean?

  one strand is methylated while the other is not

  -fully methylated strand has methyl groups bound to it
• What is loaded onto exposed replication forms?

  Dna B (helicase)
• What is the function of a DNA Primase?

  recruited by each DNA helicase and will prime the leading strand at each fork
• What is the function of the clamp loader?

  loads DNA Polymerase III along with the sliding clamp onto the DNA strand
• What is the sliding clamp? Function?

  A ring-shaped protein complex that surrounds the DNA double helix that binds to the DNA polymerase and tethers it to the DNA template
• You CANNOT replicate w/o DNA Polymerase III


  true
• What are the five rules that govern DNA polymerase III?

  -requires a primer RNA to begin synthesis (10-12bp, Free 3' OH)

  -requires a DNA template (CANNOT be RNA, instructions)

  -requires a Mg2+ cofactor

  -requires DNTP (building blocks)

  -can ONLY be synthesized in the 5' to 3' direction

  _Accuracy is credited to proof reading mechanism
• During Initiation of Replication, a replisome with contain 3 things:

  -1 helicase

  -2 polymerase III

  -2 sliding clamps
• What is a replisome function?

  ensures leading and lagging strand are synthesized at the same time in the right direction (5' to 3')
• What is the RNase H and function?

  Ribonuclease H

  -catalyzes cleavage of RNA in RNA/DNA substrate