Growth Control (14)

Question 1

What are the three main factors that control growth?

Answer 1

1- Cell lineage
2- External/ Diffusible Factors
3- Cell-cell/ Cell- ECM interactions

Question 2

What is cell lineage?

Answer 2

Internal control of G1/S transition

Question 3

When does apoptosis occur?

Answer 3

During normal development and also in adulthood

Question 4

Why does apoptosis occur?

Answer 4

It is usually a result of checkpoint error during DNA replication/ cell cycle

Question 5

What are three examples of apoptosis during normal development?

Answer 5

1- Formation of the digits
2- Epithelial cells during palate fusion
3- Neurons in developing brain

Question 6

Name two examples of apoptosis that occurs in normal adult cells?

Answer 6

1- Lining of the gut

2- Mammary tissue post-lactation (due to hormone deprivation)

Question 7

What is the fol of apoptosis during the development of the brain?

Answer 7

To control the number of neuros. Cell death matches the number of nerve cells to number of target cells.

Trophic signals are required for cell survival.

Question 8

Describe the morphology that an apoptotic cells?

Answer 8

They shrink, then form membrane blebs and then fragment, releasing small membrane-bound apoptotic bodies that are phagocytosed by macrophages

Question 9

What happens to necrotic cells?

Answer 9

They swell and burst

Question 10

Which cells are usually associated with inflammation….Necrotic cells or apoptotic cells?

Answer 10

Necrotic cells

Question 11

What is Bad allowed to do when there are no trophic factors present?

Answer 11

Bad can interact with the anti-apoptotic proteins….Bcl2 and Bclxl

Question 12

Where are Bcl2 and Bclxl located?

Answer 12

Outer mitochondrial membrane

Question 13

What does the interaction of Bad with Bcl2 and Bclxl inhibit?

Answer 13

The interaction of Bcl2 and Bclxl with Bax is inhibited?

Question 14

What happens when the Bax is not inhibited?

Answer 14

Bax containing ion channels form and the release of cytochrome C from the mitochondria into the cytosol. This results in the activation of a series of cysteine proteases called caspases.

Question 15

What is the action of caspases?

Answer 15

They digest important intracellular structural proteins such as the nuclear lamins and cytoskeletal proteins leading to the cells demise and fragmentation

Question 16

What is terminal differentiation?

Answer 16

Cell stops dividing and express a novel set of genes for specialized function

Question 17

What is senescence?

Answer 17

Ceasing cell division due to absence of telomerase

Question 18

What is telomerase?

Answer 18

A ribozyme (part protein, part RNA)

It adds a 6 base repeat to parental DNA strand and permits the completion of synthesis of the lagging strand

Question 19

True or False: Most adult somatic cells have telomerase.

Answer 19

False….most lack telomerase

Question 20

How is senescence activated?

Answer 20

When telomeres get too short, p53 is activated and then this activates p21 CDK inhibitor

Question 21

What is the function of p21 CDK inhibitor?

Answer 21

It blocks the cell in G1t

Question 22

Give an example of a growth factor that acts locally

Answer 22

Platelet derived growth factor is released from activated platelets and this stimulates wound repair

Question 23

Give an example of a growth factor that works systemically?

Answer 23

Erythropoietin which is synthesized in the kidney…this stimulates RBC differentiation in bone marrow

Question 24

What is the importance of anchorage- dependent cell growth?

Answer 24

It provides cell surivial signals to preventapoptosis

Question 25

What is contact inhibition?

Answer 25

Cell-density dependent growth inhibition (when the cells touch they stop growing)

Question 26

Nerve and cardiac muscle cells are examples of _______ cells.

Answer 26

Permanent cells

Question 27

If cells regenerate, what do they regenerate from?

Answer 27

Undifferentiated stem cells. They replace differentiated cells that cannot divide

Question 28

Describe the organization of the skin epidermis is maintained?

Answer 28

1- Stem cells attached to basal lamina continue to divide as long as the cells are anchoraged 2- Decrease in integrins/ Focal adhesions/ hemi-desmosomes 3- Detached cells stop proliferation and this drives differentiation 4- Increased caderins/keratins/ desmosomes 5- Provides strength/ barrier characteristics of skin 6- Cells die/ flatten but continue to function as barrier 7- Sloughed off and replaced

Question 29

Growth control is a balance of _______ and _________ signals.

Answer 29

Stimulatory and inhibitory

Question 30

What is different in transformed cancer cells?

Answer 30

Do not senesce Lack growth factor dependence Lack anchorage dependence No cell-cell contact inhibition

Question 31

What are the two main classes of mutation that affect the function of proteins involved in growth regulatory signal transduction pathways?

Answer 31

Oncogenes and tumor suppressor genes

Question 32

What are oncogenes?

Answer 32

Mutated or overexpressed versions of genes normally found in cellular genomes

Question 33

What where the first discovered oncogenes?

Answer 33

Viral oncogenes in retroviruses

Question 34

Generally, what are the functions of proto-oncogenes?

Answer 34

They are proteins that normally stimulate growth/ cell proliferation 2- Conversion to an oncogene result in

Question 35

True or False: Mutation of a single allele of a proto-oncogene can cause abnormal growth.

Answer 35

True

Question 36

What is the normal function of tumor suppressor genes?

Answer 36

Normally function to oppose the activity of proto-oncogenes...they normally inhibit growth

Question 37

How many alleles of a tumor suppressor gene must be mutated or deleted before uncontrolled growth occurs?

Answer 37

Both alleles

Question 38

True or False: First mutation/ deletion of Tumor suppressor genes is often inherited- individuals are predisposed to developing cancer.

Answer 38

True

Question 39

What is retinoblastoma (Rb)? What happens when it is lost?

Answer 39

A negative regulator of gene transcription. When it is lost there us unregulated transcription

Question 40

What are the functions of p53?

Answer 40

Induces synthesis of a G1, CDK inhibitor (p21) Blocks Rb phosphorylation May induce apoptosis/ senescence

Question 41

What does HPV produce that inhibits Rb and p53?

Answer 41

E6= Rb E7= p53

Question 42

What does SV40 virus produce that bind Rb and p53?

Answer 42

Large T antigen

Question 43

What are the general stages of cancer progression?

Answer 43

Loss of cell division/ growth control Ability to invade and metastasize