Study Guide Microbial Genetics (pt2) Flashcards Preview

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Flashcards in Study Guide Microbial Genetics (pt2) Deck (19)
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1
Q

Explain strand direction, in regards to DNA?

A

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.

2
Q

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?

A

antiparallel

3
Q

Describe DNA replication

A
  1. Replication forks - form where short lengths of DNA unwind.
  2. DNA polymerase - binds to DNA and inserts nucleotides, generating a new strand
  3. “Leading” Strand - the newly growing strand with the 3’ end of the exposed nucleotide growing toward the replication fork
  4. “Lagging” Strand - is the strand having the 5’ end of the exposed nucleotide facing the replication fork, growing away from the replication fork
  5. The new double-stranded DNA - re-winds into a helix as the parental DNA unwinds exposing more nucleotides to be replicated
4
Q

In DNA replication, how are nucleotides added to the strand; in what order and direction?

A
  • Nucleotides are always added to the exposed 3’ end of the growing strand
  • The strand grows in the 5’ to 3’ direction
5
Q

How is DNA unwound?

A

Unwinding is due to action of enzymes such as helicase and DNA gyrase which break the hydrogen bonds between bases

6
Q

How fast can E.colie Replicate?

A

About 1000 nucleotides per second

7
Q

E. coli DNA contains about ______ genes

A

4000

8
Q

In DNA replication, why is the “leading” strand continuously replicated?

A

because of enzymatic simplicity and ease of access to the molecule

9
Q

In DNA replication, what is needed to initiate the “lagging” strand growth in the absence of a nucleotide having a 3’ binding site?

A

RNA primer and RNA polymerase are needed to initiate strand growth

10
Q

In the DNA replication of the “lagging” strand, what happens after an RNA primer is in place, thus providing a 3’ site?

A

DNA polymerase takes over the replication and continues to within one nucleotide of the existing, previously generated strand.

11
Q

In the DNA replication of the “lagging” strand, Can DNA polymerase join the final nucleotide of the new fragment to the existing strand?

A

No. Because it cannot facilitate linking to both 3’ and 5’ binding sites.

12
Q

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?

A

DNA ligase

13
Q

What is a large, single stranded molecule of neculeotides attached to the sugar, ribose?

A

RNA

14
Q

What is RNA composed of?

A
  1. Messenger RNA
  2. Transfer RNA
  3. Ribosomal RNA
15
Q

What carries the genetic code from the DNA to the ribosome?

A

Messenger RNA

16
Q

What are three nucleotides on the mRNA that specify the amino acid to be placed in a polypetide?

A

Codons

17
Q

3 nucleotides = ?

A

1 codon

18
Q

1 codon =

A

1 amino acid

19
Q

What is the triplet code in RNA known as?

A

Genetic code