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Microbiology: Exam 2 > Microbial Genetics > Flashcards

Microbial Genetics Flashcards

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1
Q

Semiconservative Replication

A

2 strands of the double helix separate during DNA replication, and each new strand serves as a template from which the new complimentary strand is copied. ( a hybrid of parental and daughter strand).

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2
Q

Conservative

A

Parental DNA strands remain associated in one DNA molecule while new daughter strands remained associated in newly formed DNA.

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3
Q

Dispersive

A

All resulting DNA strands have regions of double stranded parental DNA and regions of double stranded daughter DNA.

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4
Q

Central Dogma

A

The pathway from DNA > RNA > Protein results in expression of genes.
It’s conserved in all cellular forms of life.

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5
Q

Leading Strand

A

Complementary to the 3”-5” parental DNA strand, is continuously synthesized toward the replication fork because polymerase can add nucleotides in this direction.

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6
Q

Okazaki Fragments

A

Small DNA sequence fragments separated by RNA Primer.

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7
Q

Lagging Strand

A

Uses Okazaki fragments and it’s synthesis is discontinuous, it needs a new primer for each of the short fragments. It’s overall directions is 5”-3”.

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8
Q

Initiation of replication

A

Occurs at a specific nucleotide sequence call “the origin of replication”

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9
Q

Origin of replication

A

Where various proteins bind to begin the replication process

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10
Q

Topoisomerase

A

Enzymes that change the shape and supercooling of the chromosomes.

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11
Q

Topoisomerase II “DNA gyrase”

A

Relaxes the supercoiled chromosome to allow DNA replication to begin.

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12
Q

Helicase

A

An enzyme that separates the DNA strands by breaking the hydrogen bonds between the nitrogenous base pairs.

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13
Q

Replication forks

A

As DNA opens up these Y-shaped structures are formed. Two are formed at the origin of replication and formation of a structure that looks like a bubble when viewed w/ electron microscope (replication bubble).

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14
Q

Single stranded binding proteins

A

DNA near the fork is coated, to prevent the single stranded DNA from rewinding into a double helix.

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15
Q

Primer

A

RNA sequence that provides the free 3” OH end allowing the start of DNA synthesis. It’s 5-10 nucleotides long and complementary to the parental or template DNA.

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16
Q

Primate

A

Synthesizes the primer. it’s a RNA polymerase.

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17
Q

Elongation

A

Addition of nucleotides occur at the max rate of 1,000 nucleotides per second.

18
Q

Sliding clamp

A

Protein that holds DNA polymerase in place as it continues to add nucleotides

19
Q

Exonuclease

A

Primers are removed by exonuclease activity of DNA polymerase 1 and the gaps are filled in

20
Q

DNA Ligase

A

Enzyme that seals the nick that remains between the newly synthesized DNA and the previously synthesized DNA, it catalyzes the formation of covalent phosphodiester linkage between the 3” OH end of one DNA fragment and 5” phosphate end of the other fragment, stabilizing the sugar phosphate backbone of DNA.

21
Q

Termination of DNA Replication

A

Occurs when the complete chromosome has been replicated

22
Q

Concatenated

A

Following replication the circular DNA chromosomes are interlocked and must be separated from each other. Accomplished through bacterial toooisomerase IV.

23
Q

Pre-replication complex (eukaryotes)

A

At the location of origin of replication, it’s composed of several proteins including helicase forms and recruits other enzymes involved in the initiation of replication.

24
Q

Ribonuclease H (RNAse H)

A

(Eukaryotes)
Removes the RNA primer which is then replaced with DNA molecules. Remaining gas are sealed by DNA Ligase.

25
Q

Telomeres (eukaryotes)

A

The end of the linear chromosomes and consist of no coding repetitive sequences. Protect coding sequences from being lost as cells continue to divide.

26
Q

Telomerase (eukaryotes)

A

Contain a catalytic part and a built in RNA template. Attached to the end of the chromosome, and complementary bases to RNA template are added to the 3” end of DNA strand.

27
Q

Bacterial vs. Eukaryotic Replication

A

Bacteria:
-single circular chromosome
-single origin per chromosome
-1000 nucleotides per second (replication rate)
-telomerase not present
-RNA primer removal by DNA poly 1
-Strand elongation by DNA poly III

Eukaryotes:
-multiple linear chromosomes
-multiple origins per chromosome
-100 nucleotides per sec. (Replication rate)
-telomerase is present
-RNA primer removal by RNAse H
-strand elongation by poly a and poly E

28
Q

Rolling circle Replication

A

Is a type of rapid unidirectional DNA synthesis of a circular DNA molecule used for the replication of some plasmids.

29
Q

Transcription (plasmids)

A

The info encoded within the DNA sequence of one or more Genoese is transcribed into a strand of RNA “RNA transcript”. The ssRNA is composed of ribonucelotides containing ACGU

30
Q

Antisense Strand (plasmids)

A

Transcription of a particular gene always proceeds from one of the two DNA strands that act as a template.

31
Q

Sense strand (plasmids)

A

The RNA is complimentary to the template strand of DNA and is almost identical to this non template strand.

32
Q

Bacteria vs. eukaryote transcription

A

Bacteria:
-# of poly encoded per mRNA is monocistronic or polycistronic
-strand elongation is core+o=holoenzyme
-no addition of 5” cap
-no addition of 3” poly A tail
-no splicing or pre-mRNA

Eukaryotes:
-# of poly encoded per mRNA is exclusively monocistronic
- strand elongation is RNA poly I, II, or III
- there’s addition of 5” cap
-there’s addition of 3” poly A tail
-there’s splicing of pre-mRNA

33
Q

Monocistronic

A

Eukaryotic mRNA encode only a single polypeptide

34
Q

Polycistronic

A

Often prokaryotic mRNAS of bacteria and archaea, encode multiple polypeptides

35
Q

Bacteria vs. Eukaryotes Translation

A

Bacteria
-ribosome are 70S (30S+50S)
-amino acid carried by initiator tRNA is fMet
- shine dalgarno sequence in mRNA is present
- there is simultaneous transcription and translation

Eukaryotes:
- ribosome is 80S (40S + 60S)
- amino acid carried by initiator tRNA is Met
- there is not simultaneous transcription and translation.

36
Q

Degeneracy

A

A given amino acid is encoded by more than one codon. (Redundancy)

37
Q

Genetic Code

A

The relationship between an mRNA codon and its corresponding amino acid.
Each amino acid is defined within the mRNA by a triplet of nucleotides called “codon”

38
Q

Wobble position

A

3rd position in a codon, less critical than first 2 which determine the amino acid.

39
Q

Process of translation in bacteria

A

1) initiation- transitional complex form and tRNA brings first amino acid in polypeptide chain to bind to start codon on mRNA
2) elongation- tRNAs bring amino acids one by one to add to polypeptide chain
3) termination- release factor recognizes stop codon, translational complex dissociates and completed polypeptide is released
4) components are recycled

40
Q

Exons

A

Genes that encode polypeptides are composed of coding sequences

41
Q

Introns

A

Intervening sequences. RNA sequences corresponding to introns don’t encode regions of functional polypeptides and are removed from pre-mRNA, then exons are joined.

42
Q

RNA splicing

A

Process of removing intron-encoded RNA sequences and reconnecting those encoded by exons. Facilitated by the action of “spliceosome” containing small nuclear ribonucleo proteins (snRNPs).

Microbiology: Exam 2 (6 decks)

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