Study Guide Microbial Genetics (pt2) Flashcards
Explain strand direction, in regards to DNA?
the end in which no phosphate is bound to the 3’ carbon of the sugar is called the 3’ end; the end in which the phosphate is bound only to the 5’ carbon is called the 5’ end.
In regards to DNA, when two strands run in opposite directions; i.e. the nucleotide of the 3’ end of one strand pairs up with the nucleotide of the 5’ end of the adjacent strand. What is this knwon as?
antiparallel
Describe DNA replication
- Replication forks - form where short lengths of DNA unwind.
- DNA polymerase - binds to DNA and inserts nucleotides, generating a new strand
- “Leading” Strand - the newly growing strand with the 3’ end of the exposed nucleotide growing toward the replication fork
- “Lagging” Strand - is the strand having the 5’ end of the exposed nucleotide facing the replication fork, growing away from the replication fork
- The new double-stranded DNA - re-winds into a helix as the parental DNA unwinds exposing more nucleotides to be replicated
In DNA replication, how are nucleotides added to the strand; in what order and direction?
- Nucleotides are always added to the exposed 3’ end of the growing strand
- The strand grows in the 5’ to 3’ direction
How is DNA unwound?
Unwinding is due to action of enzymes such as helicase and DNA gyrase which break the hydrogen bonds between bases
How fast can E.colie Replicate?
About 1000 nucleotides per second
E. coli DNA contains about ______ genes
4000
In DNA replication, why is the “leading” strand continuously replicated?
because of enzymatic simplicity and ease of access to the molecule
In DNA replication, what is needed to initiate the “lagging” strand growth in the absence of a nucleotide having a 3’ binding site?
RNA primer and RNA polymerase are needed to initiate strand growth
In the DNA replication of the “lagging” strand, what happens after an RNA primer is in place, thus providing a 3’ site?
DNA polymerase takes over the replication and continues to within one nucleotide of the existing, previously generated strand.
In the DNA replication of the “lagging” strand, Can DNA polymerase join the final nucleotide of the new fragment to the existing strand?
No. Because it cannot facilitate linking to both 3’ and 5’ binding sites.
In the DNA replication of the “lagging” strand, what can facilitate linkage of a nucleotide to both 3’ and 5’ binding sites simultaneously, and insert a nucleotide to join the newly replicated fragment with the existing strand?
DNA ligase
What is a large, single stranded molecule of neculeotides attached to the sugar, ribose?
RNA
What is RNA composed of?
- Messenger RNA
- Transfer RNA
- Ribosomal RNA
What carries the genetic code from the DNA to the ribosome?
Messenger RNA
