4rt Tema

Question 1

Which are the seven types of genomes in the Baltimore classification?

Answer 1

1. Double-stranded DNA
2. SIngle-stranded DNA
3. Double-stranded RNA
4. Positive-stranded RNA
5. Negative-stranded RNA
6. Positive-stranded RNA with reverse transcriptase activity
7. Double-stranded DNA with gaps.

Question 2

What is the purpose of this much variety and diversity of virus?

Answer 2

We don’t know exactly. It’s a result of viral evolution.

Question 3

Is one configuration more advantageous than another?

Answer 3

For some viruses, at a certain moment of its evolution, yes. Some viruses have some advantages upon others.

Question 4

Example of dnDNA

Answer 4

Adenovirus and Herpes simplex virus

Question 5

Example of ssDNA

Answer 5

Parvovirus

Question 6

Example of dsRNA

Answer 6

Reovirus and Rotavirus

Question 7

Example of RNA +

Answer 7

Picornavirus (Poliovirus=Human)

Question 8

Example of RNA -

Answer 8

Influenza virus and Ebola virus

Question 9

Example of dsDNA with gaps

Answer 9

Hepatitis B virus

Question 9

Example of (+) RNA with a (-) intermediate

Answer 9

Retrovirus

Question 10

Does DNA viruses have larger genomes than RNA viruses?

Answer 10

Yes, in general. Because they can afford it. RNA viruses don’t have proofreading activity, so in the replication process they make a mistake every 1/1000 nucleotides. If the genomes were very long, they would accumulate lots of mutations.

Question 11

How can some viruses with such small genomes have all the proteins they require to replicate?

Answer 11

They have their tricks to carry that through.
(crec que va relacionada amb una altre pregunta)

Question 12

How many amino acids will produce 1000 nucleotides?

Answer 12

The answer is 333 amino acids.

Question 13

How does HIV manage to obtain all the different proteins it needs to replicate?

Answer 13

By using different ORFs. We can observe three possible ORFs. Each gene (gag, env and pol) will produce different polyproteins.

Question 14

How many types there are of HIV?

Answer 14

two types, HIV-1(most important) and HIV-2

Question 15

Which type of virus is the Hepatitis C virus?

Answer 15

It’s a (+) single-stranded virus with very few genes (7 genes in total).

Question 16

Which type of virus is the Hepatitis B virus?

Answer 16

This genome corresponds to the seventh group of viral genomes, the one that was described after Baltimore: it’s double-stranded with gaps (the negative strand is complete, while the positive strand is uncompleted). Its genome encodes 4 different proteins (so, 4 ORFs).

Question 17

How many types of genes there are?

Answer 17

3, There are immediate early genes (first ones to be transcribed), early genes (they are transcribed a little bit after the immediate early genes) and late genes (last ones to be transcribed)

Question 18

What is produeced by immediate early genes and early genes?

Answer 18

immediate early genes and early genes produce non-structural proteins (such as transcription factors, enzymes…)

Question 19

What is produeced by late ganes?

Answer 19

Late ganes produce structural protins.

Question 20

What information is encoded in a viral genome?

Answer 20

Gene products and regulatory signals for:
- Replication of the viral genome
- Assembly and packaging of the genome
- Regulation and timing of the replication cycle
- Modulation of host defences
- Spread to other cells and hosts

Question 21

What information is not encoded in a viral genome?

Answer 21

• No genes encoding the complete proteins synthesis machinery.
• No genes encoding proteins involved in energy production or membrane biosynthesis (except Mimivirus)
• No classical centromeres or telomeres found in standard host chromosomes.
• Probably we haven’t found them yet

Question 22

Which are the two types of genomes?

Answer 22

• Genomes copied by host DNA polymerase
• Genomes encode DNA polymerase

Question 23

How are called the diferent types of genes of the herpes virus?

Answer 23

immediate early genes are called  (alpha), early genes are called  (beta) and late genes are called  (gamma).

Question 24

How the Reoviridae family is more stable?

Answer 24

They have a double capsid. So, when the virus enters the endosome, it loses the outer capsid.

Question 25

Does all mRNA genomes have a cap and a poly A tail?

Answer 25

In general yes, but ther’s an exception, the Picornaviridae family. Instead of having a cap at the 5’ end, they have an IRES (Internal Ribosomal Entry Site), which is analogue to the cap. In fact, it’s even more efficient because the virus that have this do not require the whole translational machinery.

Question 26

P1 and P2 are….

Answer 26

non-structural proteins

Question 27

P3 are….

Answer 27

structural proteins

Question 28

What does it means that a viral genome is ambisense?

Answer 28

It means that it has a positive part ans a negative one.

Question 29

Can the viral genom be segmented, non-segmented, or both?

Answer 29

This viral genome can be segmented or one-single chain (non-segmented).
For example, Orthomyxoviridae family, as an example of segmented genomes; and Paramyxoviridae and Rhabdoviridae, as an example of non-segmented genomes.

Question 30

Does DNA viruses and RNA viruses need to enter to the nucleus

Answer 30

DNA viruses enter the nucleus (except Poxviridae family virus) and RNA viruses, as they have to carry their RNA polymerase, they don’t need to enter the nucleus (everything happens in the cytoplasm).

Question 31

What does it mean antigenic drift?

Answer 31

Antigenic drift: Small variations in the genome, punctual mutations, that happen every year. That’s why people need to be vaccinated every year

Question 32

What does it mean antigenic shift

Answer 32

It happens every 30 years. This is a big change that makes a new virus. This results in the production of new viral particles, antigenically different. This phenomenon is what starts a pandemic.

Question 33

Are ambisense genomes segmented?

Answer 33

Ambisense genomes are segmented: one end of a segment is negative (it will behave as a negative strand RNA) and the other end is positive. The negative end will serve as template to produce mRNA, which will be translated into a protein called N protein.

Question 34

WHich is the function of N protein

Answer 34

This protein (non-structural) will head to make a copy of the whole genome, meaning the production of the replicative intermediary. After that, the end of the segment of the replicative intermediary that was negative, now is positive and viceversa.

Question 35

Is GPC protein non-structural?

Answer 35

NO, is strucutral, This replicative intermediary, will be used as template to produce new copies of the genome.

Question 36

How it can be distinguished the end of one part and the start of the other of ambisiense genomes?

Answer 36

There are structural differences. There’s like a hairpin that separates the negative strand from the positive one.

Question 37

WHat allows the retroviral gene called syncytium?

Answer 37

allows the virus to form syncitiums. It’s very important for the formation of the placenta.

Question 38

How can we have a complete virion with a mutated genome?

Answer 38

This happens when we have multiplicities of infections larger than one. In this case, the wild-type genome will act as a helper of the mutated genome.