L4 Differentiation

Question 1

What makes cells different from each other?

Answer 1

Changes in gene expression underliw the diversity of cll types in the body.

Question 2

What does cell diversity primarily result from?

Answer 2

Cell diversity primarily results from differences in gene expression

Question 3

All cells have the same gene content ….?

Answer 3

All cells have the same gene content, but different sets of proteins

Question 4

What does terminally differentiated state mean?

Answer 4

Refers to the final stage of cellular differentiation. They are dedicated to performing their specific roles within the organism

Question 5

What do cells change their expression profile in response to?

Answer 5

Cells change their expression profile in response to signals and other cues in the environment

Question 6

Do cells express a fraction of their gene?

Answer 6

Yes

Question 7

In what state do cells often express different genes?

Answer 7

In a disease state.

Question 8

What do stages of differentiation correlate with?

Answer 8

It correlates with stepwise expression of different regulatory transcription factors

Question 9

What are the 5 stages of potency within cells?

Answer 9

• Totipotent
• Pluripotent
• Multipotent
• Bipotent
• Unipotent

Question 10

What is the highest level of potency?

Answer 10

Totipotent. A totipotent cell can differentiate into any cell type.

Question 11

What is differential gene expression?

Answer 11

If different cells have differences in gene expression it is called differential gene expression.

Question 12

Does the level of transcription affect the level of expression?

Answer 12

Yes, increasing the level of transcription tends to increase the expression of a gene

Question 13

What does transcriptome mean?

Answer 13

All the genes that are actively being transcribed.

Complete set of RNA transcripts produced by the genome of an organism

Question 14

What is proteome?

Answer 14

Complete set of proteins expressed by a genome

Question 15

What do DNA binding proteins bind to?

Answer 15

DNA binding proteins bind to the DNA backbone and reach into the major groove to form very specific bonds.

Question 16

What are the other names for a binding site?

Answer 16

1. Cis acting element
2. Regulatory element
3. Enhancer
4. Silencer

Question 17

What is a binding site?

Answer 17

A binding site is a stretch of DNA with a sequence that is recognised and bound by the transcription factor. The bonds are H - bonds and are not stable

Question 18

Silencers are the binding site for what?

Answer 18

They are the binding site for transcriptional repressors

Question 19

What are enhancers?

Answer 19

They are a binding site for transcriptional activators.

Question 20

Give me examples of inputs that can be referred to as a genetic switch

Answer 20

Strongly activating assembly, strongly inhibiting protein, spacer DNA, weakly activating protein assembly

Each switch is responding to extrinsic or instrinsic regulation

Question 21

What is an expression profile?

Answer 21

It essentially provides a snapshot of which genes are actively being transcribed in a cell or tissue at a particular time

Question 22

Can a single transcription factor create an expression profile ?

Answer 22

Yes

Question 23

Are enhancers promiscuous?

Answer 23

Yes, they will work on any gene

Question 24

How do trancriptional factors bind?

Answer 24

They bind in clusters.

Question 25

What does "Enhancer are promiscuous" mean?

Answer 25

This means that they will work on any gene.

Question 26

Are transcriptional factor specific to a single gene?

Answer 26

No they are diverse in selection of gene.

Question 27

In summary, what is transcription factor activity dependent on? (3)

Answer 27

Extrinsic signals Intrinsic factors Regulatory binding sites

Question 28

Give me 4 examples of muscle specific proteins

Answer 28

Muscle - specific actin Myosin II Tropomyosin - Muscle-specific enzymes (e.g. creating phosphate kinase)

Question 29

What is MyoD? (Check)

Answer 29

Gene and transcription factor

Question 30

What does transfect mean?

Answer 30

Transfect = introduce a modified gene into cells or an animal (to make a transgene)

Question 31

Give me some features of MyoD

Answer 31

- Transcription factor - Expressed only in muscle precursors and muscle cells - Controls expression of genes for muscle differentiation - Maintains its own expression

Question 32

What was the experiment used to find out whether MyoD is sufficient for muscle cell differentiation?

Answer 32

Experiment: transfect fibroblasts with activated MyoD gene

Question 33

What was the result and conclusion for the sufficiency experiment?

Answer 33

Result: fibroblasts now differentiate into muscle Conclusion: MyoD is sufficient to direct muscle cell fate in fibroblasts

Question 34

Define differentiation?

Answer 34

Differentiation is a multi-step process that involves extrinsic cues and the sequential expression of different transcription factors.

Question 35

Do fibroblasts normally express MyoD or other specific proteins?

Answer 35

No, fibroblasts do not normally express them

Question 36

What are the three steps in muscle cell differentiation?

Answer 36

1. Determination 2. Differentiation 3. Maturation

Question 37

If a mice lacking both MyoD and Myf5 genes, what affects does this have?

Answer 37

Mice will lack all skeletal muscles, so both genes do have an important role in muscle differentiation

Question 38

What’s the difference between genes being sufficient or necessary/ required?

Answer 38

A gene is required for a particular process or outcome of that process cannot occur without the gene’s presence A gene is sufficient for a particular process or outcome if its presence alone is enough to cause that process to occur

Question 39

In the embryo where does most muscle cells comes from?

Answer 39

They come from somites.

Question 40

In adults where does muscle cells come from?

Answer 40

In the adult, muscle cells are renewed by satellite stem cells that line muscle fibres

Question 41

Explain how blood cells are another classic model for differentiation

Answer 41

1; in the mammalian embryo M blood cells are first made in the yolk sac and then the live. In adults, blood is made in the bone marrow. As cells travel toward terminal differentiation, they express different sets of transcription factors