A2.3 Viruses + DNA replication (BOOK)

Question 1

For enveloped viruses, what type of cell do they usually infect?

Answer 1

Animal cells

Question 2

In which reproductive cycle (?) of viruses are lipid envelopes common to?

Answer 2

Lytic cycle (because of lysis)

Question 3

Describe the bacteriophage lambda on terms of the type of virus

Answer 3

Bacteriophage
- bacterium/arcaheum hosts

Question 4

Is the bacteriophage lambda enveloped or non-enveloped?

Answer 4

Non-enveloped

Question 5

What is the genetic material of bacteriophage lambda?

Answer 5

• Double stranded DNA
• both negative and positive strands
  -32 genes for 29 proteins
  -4 enzymes

Question 6

Give the distinctive features of the bacteriophage lambda

Answer 6

• lytic cycle OR lysogenic cycle

Question 7

What is the host of the Bacteriophage Lambda?

Answer 7

e. coli

Question 8

Give the parts of the bacteriophage lambda.

Answer 8

Question 9

Describe COVID-19 (Type of Virus)

Answer 9

• coronavirus
• crown-like
• animal cell host

Question 10

COVID-19 (Enveloped or Non-Enveloped)

Answer 10

Enveloped

Question 11

COVID-19 (Genetic Material)

Answer 11

• 1 stranded positive sense RNA
• 16 genes: 29 proteins
• 6 enzymes

Question 12

COVID-19 distinctive features

Answer 12

• Zoonosis
• from a bat

Question 13

Host of COVID-19

Answer 13

Human cells and other epithelium mammal cells

Question 14

HIV type of virus

Answer 14

• retrovirus

Question 15

HIV enveloped or non-enveloped

Answer 15

Enveloped

Question 16

HIV genetic material

Answer 16

• 2 copies of a single-stranded positive sense RNA
• 9 genes: 15 viral proteins
• 4 enzymes

Question 17

Host of HIV

Answer 17

T-Helper cells in the human immune system

Question 18

Give the parts of COVID 19

Answer 18

Question 19

give the parts of HIV

Answer 19

Question 20

For the lytic cycle, after lysis, how many viruses pop out?

Answer 20

~100

Question 21

How many times is the viral DNA replicated in the lytic cycle?

Answer 21

• around 100 times by a rolling circle method

Question 22

What are the two enzymes in HIV that cause mutations ?

Answer 22

• reverse transcriptase (for retroviruses only)
• cytidine deaminase (general)

Question 23

Why do mutations happen more often in viruses in regards to enzymes?

Answer 23

• They don’t proofread

Question 24

Define cytidine deaminase

Answer 24

enzyme that converts cytosine to uracil

Question 25

Why does HIV have the highest known mutation rate of any virus?

Answer 25

- reverse transcriptase - cytidine deaminase

Question 26

Describe the influenza virus

Answer 26

- enveloped - negative sense RNA - uses RNA replicase -> high mutation rate - haemagglutinin protein to bind to a host cell - neuraminidase to help with release into host cell

Question 27

What is the rule that one nitrogen base must always pair with the other?

Answer 27

Complementary base pairing

Question 28

What is the duty of DNA polymerase I?

Answer 28

- exonuclease - break bonds between nucleotides and polymerase by linking nucleotides - replaces RNA nucleotides w/ DNA nucleotides

Question 29

DNA ligase duty

Answer 29

- Seal the nicks left by DNA polymerase I

Question 30

How many times on a leading strand is the primer added?

Answer 30

- 1 time

Question 31

How many times are RNA primers added to the lagging strand?

Answer 31

every 100-200 times

Question 32

In prokaryotes, who proofreads the DNA replication process and how?

Answer 32

- DNA polymerase III - removes incorrect nucleotide - moves back 1 nucleotide - then inserts the CORRECT nucleotide

Question 33

Describe the procedure of the Messelsohn-Stahl Experiment

Answer 33

- Uses E. Coli which makes DNA molecules from nitrogen compounds in their food - TRANSFERRED TO 15N -> 14N (old -> new) -> density - DNA molecules centrifuged - After first cell division: Mixed density (old + new) - After second: Mixed density + light density (mixed + just new)

Question 34

Conclusion of Messelsohn-Stahl

Answer 34

- DNA is semi conservative

Question 35

Define dispersive

Answer 35

Each individual DNA strand is a “patchwork” of original and new DNA

Question 36

Describe gel electrophoresis

Answer 36

- separates DNA fragments by length - gel placed in tank with electrolyte solution - DNA samples in *wells* - negative to positive movement - larger DNA molecules lesser + opp. - After, gel is treated with dye to visualize DNA - Visible *bands* - DNA ladder placed in one lane - DNA bands in other lanes

Question 37

Outline two potential applications of PCR and gel electrophoresis

Answer 37

- testing for coronaviruses - DNA profiling for paternity testing

Question 38

Describe how PCR can be used to test for coronavirus

Answer 38

- swab in nose or throat - RNA -> DNA BY REVERSE TRANSCRIPTASE - PCR to amplify specific viral base sequences that are markers - fluorescent markers are attached to any DNA produced

Question 39

Give the advantages and disadvantages of using PCR and gel electrophoresis for coronavirus testing

Answer 39

- Advantage: sensitive — 1 molecule of viral DNA -> 35 bil. mol. of DNA - Advantage: primers can be designed so only 1 viral strain dectected - Disadvantage: Requires very expensive equipment - Due to time needed for thermal cycling, no immediate results