Bacterial Genetics

Question 1

What is DNA?

Answer 1

DNA is a what carries the genetic infromation.

Question 2

What makes up DNA?

Answer 2

Deoxyribose (sugar) + nitrogenous base (A,G,T, and C) + Phosphate.

Question 3

What are antiparallel strand?

Answer 3

A DNA strand that run the opposite direction

Question 4

What are some aspects of DNA replication that are unique to bacterial systems compared to that in eukaryotes?

Answer 4

Bacteria have circular chromosomes.

Question 5

How does E.coli control the initiation of DNA replication? Why is this important?

Question 6

What are the roles of DnaA and SeqA?

Answer 6

DnaA- binds fully methylated DNA to initiate DNA replication.
SeqA- binds to hemi-methylated DNA to prevent DNA replication

Question 7

List all the enzymes and components involved in DNA replication from start to finish. State the role of each of these. (Also, think about the directionality, important regions and things that bind at these regions)

Answer 7

Helicase (DnaB)- Unwinds the double stranded DNA.
DNA primase- adds RNA primer.
Gyrase (Topoisomerase II)- prevent DNA strand from recoiling together.
RNA polymerase (DNA primase) creates primer for DNA polymerase III to extend.
DNA polymerase I- remove RNA primer and replace RNA with DNA.
DNA ligase- helps to link the lagging strands fragment together.

Question 8

What happens during initiation?

Answer 8

During initiation at the origin at replication (Oric) DnaA binds Oric at DnaA boxes, DNA replication begins at the replication fork as helicase (DnaB) an enzyme that unwinds the DNA strands. As helicase unwinds the DNA, primers are being added by DNA primase which reads from 5’>3’ and single stranded binding proteins help separate strands from re-annealing. As well as gyrase (topoisomerase II) make sure that the DNA strand is disentangle.

Question 9

What happens during elongation?

Answer 9

During elongation DNA polymerase is attached to the template strand begins to create new DNA strands from 5’>3’. Then the template strand is read from 3’>5’ and leading strand (continuous) newly synthesized DNA is formed from 5’>3’. The helix continues to unwind and lagging strand (fragments) is synthesized from 3’>5’.

Question 10

What is transcription and what occurs during the process of transcription?

Answer 10

Transcription is the process of by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA).

Question 11

What is translation and what occurs during the process of translation?

Answer 11

Transfer of information from the mRNA to the polypeptide.

Question 12

Compare and contrast the two ways of transcription termination.

Answer 12

Rho independent- destabilize open complex
Rho dependent- ends transcription by breaking H-B between transcript and template.

Question 13

What are the 3 stop codons and the start codon?

Answer 13

UAA, UGA, UAG

Question 14

Which amino acid does the start codon code for in bacteria?

Answer 14

AUG

Question 15

There are several reasons for the low error rate of DNA replication. Describe the ones I mentioned in class (2 enzymes and 2 repair systems).

Answer 15

DNA polymerase III & I (both proofread/ DNA poly I removes and replace RNA primer)

Question 16

How does the bacterial cell mark proteins for transport to the outside? Name and describe the system that helps with this.

Question 17

List 3 steps in DNA replication.

Answer 17

Initiation, elongation, and termination.

Question 18

In which direction does DNA polymerase start

Answer 18

5’>3’

Question 19

In which direction does DNA replication start

Answer 19

5’>3’

Question 20

What happens during termination?

Answer 20

The remaining RNA primers from initiation are then removed by DNA polymerase I from the direction it was added (5’>3’) and replace it with RNA with DNA. And DNA ligase joins the lagging strand together to complete the strand.

Question 21

DNA coding strand is what?

Answer 21

Sense strand (5’>3’)

Question 22

DNA template strand is what?

Answer 22

Anti sense strand (3’>5’)

Question 23

Leading strand

Answer 23

Is continuous and synthesized from 5’>3’

Question 24

Lagging strand

Answer 24

Known as Okazaki fragments. Fragmented requires DNA ligase and synthesized from 3’>5’

Question 25

mRNA is made

Answer 25

5’>3’

Question 26

What role does mRNA play?

Answer 26

mRNA carries the genetic information from DNA and encodes for proteins.

Question 27

What is transcription?

Answer 27

Is the process by which a cell makes an RNA copy of a piece of RNA (mRNA).

Question 28

What makes mRNA?

Answer 28

RNA polymerase II

Question 29

What is tRNA?

Answer 29

Brings amino acids during transcription.
Converts the mRNA from codon to anti-codon.

Question 30

RNA polymerase (transcription)

Answer 30

When it copies DNA information and creates RNA (mRNA)

Question 31

In RNA polymerase what are the core enzyme composed of?

Answer 31

2 identical alpha subunits, beta, beta prime, and omega.

Question 32

Sigma factor

Answer 32

Ensures transcription (RNA polymerase) starts at the correct location.

Question 33

What is a housekeeping gene?

Answer 33

Helps maintain cells function and upkeeps cells.

Question 34

Promoter

Answer 34

Specific sequence on DNA (consensus seq).

Question 35

Holoenzyme

Answer 35

Core + sigma factor.

Question 36

Transcription (Initiation, elongation, and termination)

Answer 36

Initiation- Transcription factors help the RNA polymerase attach to the correct spot on the DNA
Elongation-Polymerase zooms down the antisense strand putting the correct nucleotides in order, making a long mRNA strand.
Termination- When RNA polymerase reads a stop sequence of nucleotides on the DNA it cuts the mRNA loose. The mRNA goes to the ribosome.

Question 37

50s Large subunit composed of?

Answer 37

23s rRNA, 5s rRNA, and 34 proteins.

Question 38

30s Small subunit composed of?

Answer 38

16s rRNA and 16 proteins.

Question 39

How are tRNA charged?

Answer 39

Enzyme adds amino acids to tRNAs (aminoacyl tRNA synthetase)