0108100830 - Mfm Ii - Mechanisms Of Genetic Exchange (Biel)

Front 1

Transcription is what in general?

Back 1

making an RNA copy of a piece of DNA

Front 2

Transcription Step 1

Back 2

RNA polymerase binds to promoter

Front 3

Transcription Step 2

Back 3

RNA polymerase separates the two strands of DNA

Front 4

Transcription Step 3

Back 4

RNA polymerase adds ribonucleotides complementary to that of DNA

Front 5

Transcription Step 4

Back 5

RNA polymerase does this until it reaches the terminator on the DNA

Front 6

In what direction does transcription take place

Back 6

5' to 3'

Front 7

operon

Back 7

a portion of the original DNA strand corresponding to one or more gene under control of a single promoter. the promoter, gene1, gene2, terminator complex is the operon here.

Front 8

Translation step 1

Back 8

30S subunit of ribosome binds to AUG start codon

Front 9

Translation step 2

Back 9

initiator tRNA binds to 30S subunit

Front 10

Translation step 3

Back 10

50S ribosomal subunit binds to form a 70S

Front 11

Translation step 3

Back 11

P site and A site

Front 12

Translation step 4

Back 12

peptide bond forms between two amino acids one on each P and A site

Front 13

Translation step 5

Back 13

P site is no longer attached to amino acid

Front 14

Translation step 6

Back 14

elongation takes place now as the ribosome moves down the rna unit

Front 15

Translation step 7

Back 15

nonsense codon encounter and release factor binds to A site

Front 16

Describe the practical function of a tRNA molecule

Back 16

rosetta stone: each tRNA is specific to a codon on the mRNA. if a matching tRNA doesn't exist for a codon (nonsense codon), then that indicates the end of a gene. once a specific tRNA binds a specific codon, a specific amino acid is created adjacent to the tRNA. specific codon = specific AA, but tRNA is the middle man.

Front 17

Translation step 8

Back 17

ribosome is released, completing translation

Front 18

What are the start and stop points in an operon for a gene?

Back 18

The points are more functionally represented on the mRNA that is the product of transcription, which are:
Promoter starts operon
AUG start codon starts gene
Nonsense codon stops gene
Termintor stops operon

Front 19

When a signal turns transcription ON, what is that called?

Back 19

Induction, this is an INDUCIBLE system. The molecular signal is called an inducer.

Front 20

When a signal turns transcription OFF, what is that called?

Back 20

Repression, this is a REPRESSIBLE system. The molecular signal is called a corepressor

Front 21

Example of inducible system?

Back 21

lac operon uses lactose as an inducer. so when lactose is present, the enzymes needing lactose as a carbon source are made. lactose is available, enzymes are made. lac makes enzymes.

Front 22

Example of repressible system?

Back 22

trp operon uses tryptophan as a corepressor, so when tryptophan is present, no tryptophan needs to be made. trp makes tryptophan. tryptophan is there, no more needs to be made.

Front 23

What is positive control?

Back 23

a type of system transcription control where the protein that regulates transcription turns transcription on (activator) by helping RNA polymerase bind to the promoter

Front 24

What is negative control?

Back 24

a type of system transcription control where the protein that regulates transcription turns transcription off (repressor) by preventing RNA polymerase from bind to the promoter

Front 25

In the absence of lactose, the lacI gene makes a repressor protein that binds to a region of DNA
called the operator. When the repressor is bound to the operator, it prevents RNA polymerase from
initiating transcription. When lactose is present, it is converted into the inducer, allolactose. The allolactose binds to the
repressor protein and inactivates it. Now the RNA polymerase can initiate transcription and
transcribe the three lac genes.
What type of control system is the lac operon?

Back 25

The lac operon is inducible because
lactose turns it on.
It is negatively controlled because the
regulatory protein turns transcription off.

Front 26

In the absence of tryptophan, the trpR repressor is made, but is inactive. RNA polymerase can
initiate transcription and the five trp polypeptides are made.
In the presence of tryptophan, the trp repressor is active. It binds to the operator and prevents RNA
polymerase from transcribing the trp genes.
What type of control system is the trp operon?

Back 26

The trp operon is repressible because
tryptophan turns it off.
It is negatively controlled because the
regulatory protein turns transcription off.

Front 27

What type of control is the ara operon under if the following is true:
In the absence of arabinose, the activator protein is made, but is inactive. RNA polymerase can’t
initiate transcription at the promoter, and the three ara genes are not transcribed.
In the presence of arabinose, the activator protein becomes active. It binds to the activator binding
site and allows RNA polymerase to initiate transcription. The three enzymes made allow the cell to
use arabinose as a carbon and energy source.

Back 27

The ara operon is inducible because
arabinose turns it on.
It is positively controlled because the
regulatory protein turns transcription on.

Front 28

What is catabolite repression?

Back 28

it is an operons ability to selectively and heirarchically use sugars for metabolism based on preference. such ash when the lac operon uses a form of positive control by CAP regulatory protein. in the presence of glucose, CAP is not made, and so it does not assist the RNA polymerase to initiate transcription at the promoter. when glucose is absent CAP is made and acts as positive control to do just that.

Front 29

How does control mechanisms relate to MRSA?

Back 29

MRSA has a gene that if transcribed can produce an enzyme (beta-lactamase) that will break down certain antibiotics (beta-lactam antibiotics, penicillin family). The antibiotics themselves are the activators, so when you Dx an infection, culture the sample with a small amount of penicillin to inactive the repressor for the BlaZ gene so you can see the BlaZ product - beta-lactamase.

Front 30

What is transformation?

Back 30

a method of genetic exchange where a cell picks up free DNA from the environment

Front 31

What is transduction?

Back 31

a method of genetic exchange where a cell obtains DNA from a virus.

Front 32

What is conjugation?

Back 32

a method of genetic exchange where DNA is transferred directly between cells.

Front 33

What do you call a cell that is capable of transformation?

Back 33

competent

Front 34

What are 4 examples of competent bacterial species?

Back 34

Haemophilus influenzae, Streptococcus pneumoniae, Bacillis species and Neisseria species.

Front 35

What are plasmids?

Back 35

pieces of DNA, usually circular that exist in the cytoplasm of a cell, but are not integrated into the nucleoid. they are self duplicating

Front 36

What role do phages play in transduction?

Back 36

A phage will pick up DNA from one cell and inject it into another cell. The source of the DNA is the "donor," and the destination is the "recipient."

Front 37

What is specialized transduction?

Back 37

A type of transduction where a phage releases DNA into bacteria, the phage DNA is integrated into the chromosome, excises itself from the chromosome, then self duplicates as phage in the cytoplasm until lysis occurs.

Front 38

What are names for phages that undergo specialized transduction?

Back 38

Lysogenic, temperate, specialized transducing

Front 39

What is the significance of the lambda phage?

Back 39

It is a classic example of a lysogenic phage that additionally incorporates an extra 'gal' gene from the donor into it's DNA which is passes to the recipient, so that the recipient then has two 'gal' genes, which is referred to as 'Gal'

Front 40

What is the significance of the F plasmid?

Back 40

this is a plasmid that exists in bacteria cells and can be transferred by conjugation. The F plasmid containing cell is called an F+ cell and can make F pili in order to accomplish conjugation.

Front 41

What is an F- bacterial cell?

Back 41

A bacterial cell lacking the F plasmid and correspondingly cannot make F pili, nor do they need them if they don't have the plasmid.

Front 42

What is the process of conjugation with the F plasmid?

Back 42

F+ cell makes F pili that attaches to F- cell, F plamid self duplicates, and copy moves to F- cell, so that the product is F+ cells.

Front 43

What is an F' (F-prime) cell?

Back 43

A cell in which the F plasmid integrated into the chromosome, then extracted from the chromosome, but as a result, pulled a part of the chromosome out with it, so that now it has an F' plasmid.

Front 44

What is one of the primary conjugation related reasons for antibiotic resistance?

Back 44

R-plasmids that contain antibiotic resistant genes that exist in Gram(-) bacteria and can transfer between ANY Gram(-) bacteria.

Front 45

What is an insertion sequence (IS)?

Back 45

the simplest kind of transposable element in a DNA molecule. usually < 2000 bases with inverted repeats at each end which allows them to enter and exit DNA by means of a protein sequence

Front 46

What is a transposon?

Back 46

A pair of ISs with a gene in the middle. This is significant because now we can move antibiotic resistance that exists in a gene around in DNA.

Front 47

What is a conjugative transposon?

Back 47

Transposons that can move between bacterium. Bacterium do not have to be the same genus, they can also be either Gram (+) or Gram (-).