Lecture 11a

Question 1

What cells prevent us from attacking our own immune system?

Answer 1

Dendritic cells

Question 2

What are dendritic cells?

Answer 2

Immune system cells present in tissues that are in contact with the body’s external environment (skin, inner lining of the nose, lungs, stomach, and intestines) and our blood.

Question 3

What is important about the dentrites on dendritic cells?

Answer 3

Dentrites are the petal-like projections that maximize surface area and interaction with the environment.

Question 4

What do dendritic cells ingest?

Answer 4

They ingest things that do not belong near the external environment like bacteria and viruses.

Question 5

What is phagocytosis?

Answer 5

When dendritic cells ingest things that do not belong.

Question 6

After phagocytosis, what do dendritic cells do with the pathogen?

Answer 6

Dendritic cells digest the antigen, then use MHC proteins to present little bits of the antigen’s proteins on the surface of the dendritic cell.

Question 7

What else resides in the cell membrane of the dendritic cell besides MHC proteins?

Answer 7

CLR proteins are also placed in their membranes.

Question 8

What do dendritic cells have to do to get to the spleen?

Answer 8

They express a protein called CCR7 which makes the cell migrate to the spleen after it has presented the antigen using the MHC proteins.

Question 9

If it is actually a pathogen, what do dendritic cells in the spleen do?

Answer 9

They will active B and T cells that come to the MHC proteins and fight the pathogen.

Question 10

What do CLRs do on dendritic cells?

Answer 10

Dendritic cells use CLRs to recognize cells that belong to the same individual.

Question 11

What is a CLR-CLR interaction?

Answer 11

This is when the CLRs on separate dendritic cells come into contact. When this occurs, the dendritic cell knows that the proteins (antigens) are ‘self’. The dendritic cell will then acquire the antigen by ingesting a small amount of membrane.

Question 12

What is nibbling?

Answer 12

This is when a dendritic cell recognizes an antigen/proteins as being from the body and so it acquires them by ingesting a small amount of membrane from the dendritic cell it is in contact with.

Question 13

What occurs after a dendritic cell has ingested self-antigens?

Answer 13

The dendritic cell then presents the ingested antigen on its outer cell membrane and puts NEW CLR proteins on its surface.

Question 14

After ingestion of the self-antigen, why does a dendritic cell put new CLR proteins in its membrane?

Answer 14

This is to show that the dendritic cell interacted with ‘self’, that being another cell in the same individual.

Question 15

If we are a dendritic cell with an antigen on our surface, what area of the body do we wanna get to and why?

Answer 15

We wanna migrate to the spleen, because that is where the B and T cells reside.

Question 16

If we had new CLRs on the cell surface due to recognition of a ‘self’ protein/antigen, what occurs in the spleen?

Answer 16

Dendritic cells will interact with B and T cells recognizing the self antigen. The CLR proteins also interact to signal T and B cells that the antigen is NOT foreign, thus, they will NOT attack.

Question 17

Besides antibodies, what else do B and T cells have on their surface that is important in the spleen?

Answer 17

They also have CLRs present on their surface, so that the CLRs can interact between cells. This is important for the dendritic cell to signal to B and T cells not to attack.

Question 18

What is a double interaction?

Answer 18

When the CLR and presented antigen interact.

Question 19

When we have a ‘self’ antigen, what does interaction between the CLR and presented antigen (double interaction) cause?

Answer 19

This makes the B and T cells commit suicide by apoptosis. This is because they are not needed right now due to the antigen coming from our own bodies.

Question 20

T/F: Prokaryotes have several RNA polymerase.

Answer 20

False! Prokaryotes have one RNA polymerase which does RNA synthesis.

Question 21

How are bacterial promotors generally organized form the 5’ to 3’ direction?

Answer 21

At the 5’ end, there is a -35 position sequence. Then comes a -10 position sequence. More in the 3’ direction, there is the +1 position which is the transcriptional start site.

Question 22

What is the Transitional start site?

Answer 22

+1 position

Question 23

What is the promoter region?

Answer 23

From -35 position sequence to the -10 position sequence.

Question 24

T/F: Bacterial promotors show no variation.

Answer 24

False! The sequences for bacterial promotors are not always the same.

Question 25

What is the consensus sequence?

Answer 25

The most common nucleotide sequence in bacterial promotors.

Question 26

What is the relationship between consensus sequence and promotor strength?

Answer 26

The closer the nucleotide sequence to the consensus sequence, the stronger the promotor will be. If you use the consensus sequence for a promoter, the promotor will be VERY STRONG.

Question 27

What is the name for the -10 position sequence?

Answer 27

Pribnow Box

Question 28

Is core transcription used in bacteria or eukaryotes?

Answer 28

Bacterial transcription

Question 29

What is a closed complex?

Answer 29

This is when the sigma factor binds to the -35 and -10 position sequence at the promoter, which stops the movement of RNA polymerase along DNA. Strands are NOT separated.

Question 30

What makes up the complex in the initiation of bacterial transcription?

Answer 30

RNA polymerase and sigma factor form a complex.

Question 31

What is an open complex?

Answer 31

RNA polymerase changes its shape, which releases sigma factor. RNA polymerase can now separate DNA on its own. RNA polymerase will then move along the gene to make an RNA copy of the template strand.

Question 32

How many RNA polymerases do eukaryotes have? Which produces mrNA?

Answer 32

Pol I, Pol II, and Pol III. Pol II makes mRNA.

Question 33

What is the transcription called that occurs in eukaryotes?

Answer 33

Basale transcription

Question 34

What does TFIID initially do during the initiation of RNA transcription?

Answer 34

TFIID bings to the TATA box, which recruits other proteins tethering the RNA polymerase to the TATA box. Another protein and TFIIH bind to RNA polymerase II.

Question 35

What is a kinase?

Answer 35

A protein that recognizes and phosphorylates another molecule, often a protein.

Question 36

What does phosphorylation do?

Answer 36

Causes activation of the protein.

Question 37

What 2 things does TFIIH do in eukaryotic RNA transcription initiation?

Answer 37

1) Acts as a helicase to separate DNA strands (forming an open complex) 2) Acts as a kinase by also phosphorylating RNA poly II

Question 38

What does phosphorylation of RNA poly II do?

Answer 38

It causes a change in shape that releases RNA polymerase from the tether created by the transcription factors. This causes the tether to fall apart and now RNA pol II is free to transcribe.