Molecular Microbiology 8-11

Question 1

What is tRNA?

Answer 1

• tRNA is specific to recognizing each amino acid
• Binds with ATP to an amino acid-producing AMP
• its anticodon loop binds to the complementary codon on mRNA
• the 3’ acceptor arm ester bonds with the carboxylic acid of an amino acid and carries it to the ribosome site

Question 2

What is mRNA?

Answer 2

-During transcription an RNA Polymerase reads DNA and creates a complementary single RNA strand called mRNA.
-mature mRNA after splicing of exons determines the sequence of amino acids to be formed as a protein

Question 3

What is rRNA?

Answer 3

-non-coding RNA that forms the large and small subunits of the Ribosome
-In the larger subunit, it forms the peptidyl transferase, an ENZYME, that catalyzes the peptide bond formation between amino acids in protein biosynthesis (23S rNA). It also allows tRNA hydrolysis to release the protein from the tRNA and Ribosome. (can be targeted by antibiotics so bonds can’t form)

Question 4

23 sRNA

Answer 4

RNA that acts as an ENZYME, not a protein, to catalyze peptide bond formation

Question 5

Initiation

Answer 5

-at AUG start codon major and minor rRNA subunits combine into a ribosome
-Binding site upstream from start codon at GTP cap
-The initiator tRNA, carrying the first amino acid (METhionine), binds to the P-site (peptidyl site) on the Ribosome forming Initiation Complex

Question 6

Anticodon

Answer 6

-Arm of tRNA clover structure that binds to 3 complementary bases of mRNA
-Wobble Hypothesis: binds more loosely to 3rd codon allowing one tRNA to bind to more than one codon and code for the same amino acid

Question 7

Anticodon

Answer 7

-Arm of tRNA clover structure that binds to 3 complementary bases of mRNA
-Wobble Hypothesis: binds more loosely to 3rd codon allowing one tRNA to bind to more than one codon and code for the same amino acid

Question 8

Elongation

Answer 8

-the incoming tRNA anticodon binds to the A-site of the codon next to the P-site
-The ribosome moves along the mRNA in the 5’ to 3’ direction allowing the amino acids to be linked by peptide bonds in the proper direction
-mRNA sifts down a codon and the empty tRNA moves out of the P-site to exit via the E-site

Question 9

Termination

Answer 9

-Once the stop codon reaches the ribosome A-site, Release Factors (RF) cleave polypeptide from tRNA by adding a water
-Ribosome dissociates

Question 10

GTP

Answer 10

Used in translation to form peptide amino acid chains in elongation and other steps

Question 11

What is a Suppressor?

Answer 11

-A mutant tRNA that recognizes when a mRNA is wrong and if there is a stop codon brings an amino acid anyway.
-Compensates for original mutation

Question 12

What are the Parts of the Amino Acid and what give it it’s properties?

Answer 12

(Amino Group, Carboxylic Acid = all have it) and R-Group (changes based on amino acid and can be polar, np ect.)

Question 13

Gram Positive

Answer 13

Stain Purple, 1 membrane with thick membrane
Stain gets stuck in the thick cross-linked peptidoglycan cell wall

Question 14

Gram Negative

Answer 14

Stain Pink, 2 membranes with thin peptidoglycan. Ethanol decolorizer breaks down thin membrane so violet-iodine crystal can escape

Question 15

Reversion

Answer 15

A mutation in the DNA portion that corrects for a mutation
-DNA changing (phenotype might not change back bc epigenetics)

Question 16

Revertant

Answer 16

strain for mutation that restores original phenotype
Same-site: mutation at same site as original
Second-site: mutation at different site

Question 17

Truncated Protein

Answer 17

An amino acid chain that has been shortened because of a mutation - usually nonsense

Question 18

Silence Mutation

Answer 18

A point mutation in the DNA that doesn’t change the amino acid chain produced -nucleotide different, but codon codes for same amino acid

Question 19

Nonsense Mutation

Answer 19

A mutation that changes an amino acid to a stop codon so the protein chain ends early - point

Question 20

Missense Mutation

Answer 20

A mutation that causes one of the amino acids to be changed in a change - point

Question 21

Frameshift Mutation

Answer 21

An insertion or deletion of a nucleotide will shift the entire codon reading down or up and subsequently change the whole protein.
- often results in loss of protein function

Question 22

Selectable Mutation

Answer 22

• a mutation that has an advantage over a parent
  Something easy to isolate. Phenotypic level- you can see it

Question 23

Non Selectable Mutation

Answer 23

• mutation that doesn’t have an advantage
• DNA level- can’t see mutation easily

Question 24

Ames Test

Answer 24

Purpose: test to determine if something is a mutagen and how much it affects

Procedure: Plate strains on different media plates with a little of the nutrients needed to survive. In one plate place chemical being tested. If the plate with the chemical causes more colonies to grow, it is a mutagen bc it caused strain to mutate DNA and grow

-Sometimes mutagen can be created by a chemical modified by another thing. i. e. digestion through liver

Question 25

Mutagenesis

Question 26

Mutagens

Answer 26

Anything that can cause a mutation,
chemical, physical, biological

Question 27

Nucleotide Base Analog

Answer 27

A fake nucleotide base that is similar to the real one and inserts itself into the DNA
-like thymine methyl being replaced by a Bromine

Question 28

Chemical Modification

Answer 28

chemical mutagens that cause chemical modifications: Ex Nitrosoguanidine or Oxygen (produce toxic oxygen radicals reacting to DNA)

Question 29

Intercalating Agents

Answer 29

• Something that interrupts the DNA and causes a frameshift mutation
• like a flat disk that slots itself in between nucleotides
• ethidium bromide: a type of dye that stains DNA

Question 30

Auxotroph

Answer 30

An organism that can’t produce a protein that it needs to survive
- will not grow without it
- notated with a negative sign
- useful in determining mutagens with Ames Test

Question 31

Screening - Negative Selection

Answer 31

-Used for non selectable mutations
- replica plating:
-grow colonies on a primary plate
-use a printing block to stamp secondary plates with identical colonies in the same location on plates with different media/nutrients
- Compare plates to find mutant colonies: Find auxotroph and antibacterial resistance mainly

Question 32

Negative Selection

Answer 32

Technique used to isolate colonies with specific genetic mutations by eliminating/inhibiting the growth of strains with unwanted characteristics

Question 33

Positive Selection

Answer 33

Technique used to select for specific genetic mutations traits by providing a growth advantage/selective pressure for strains with the trait

Question 34

Induced Mutation

Answer 34

Mutations made environmentally or purposefully
-Ex: interaction with oxygen radicals or radiation

Question 35

Spontaneous Mutation

Answer 35

Those that occur without external cause.