Cell Differentiation And Gene Expression

Question 1

Define cell differentiation

Answer 1

The process through which a cell undergoes changes in gene expression and gene activity to specialise and take on different roles in an organism

Question 2

Is cell differentiation reversible?

Answer 2

No

Question 3

What happens to the proportions of dividing cells when humans approach maturity

Answer 3

It falls

Question 4

Define stem cells

Answer 4

Undifferentiated and unspecialised cells of the human body

Question 5

What is a totipotent cell (with an example)?

Answer 5

Able to differentiate into every cell type in the body - zygote

Question 6

What is a pluripotent cell (with an example)?

Answer 6

Able to differentiate into most, but not all cells (ie not placenta) - embryonic cells/ blastocyst

Question 7

What is a multipotent cell (with an example)?

Answer 7

Can differentiate into a limited number of cells - hematopoietic and mesenchymal cells

Question 8

What is a unipotent cell (with an example)?

Answer 8

Can only form one type of cell - sperm cells and dermocytes

Question 9

What is the asymmetric division theory of how a stem cell divides and what does it produce?

Answer 9

A fate regulator (polarity protein) distributes unequally in the daughter cells - produces one differentiated cell and one stem cell

Question 10

What is the symmetric division theory of how a stem cell divides and what does it produce?

Answer 10

Some cells may divide to give identical daughter stem cells while other stem cells divide to generate two progenitor cells committed to differentiation- two differentiated cells or two stem cells

Question 11

Where do embryonic stem cells come from?

Answer 11

A four or five day old human in the blastocyst phase of development.

Question 12

Why aren’t embryonic stem cells sometimes considered stem cells?

Answer 12

They differentiate into specialised cells so quickly

Question 13

What type of stem cells are embryonic stem cells?

Answer 13

Pluripotent

Question 14

What type of stem cells are adult stem cells?

Answer 14

Multipotent

Question 15

What is a tissue specific cell?

Answer 15

A cell that can give rise to types of differentiated cells within the tissue they reside in

Question 16

What is the function of adult stem cells?

Answer 16

To replace dead cells

Question 17

What are the levels of adult stem cells like?

Answer 17

In low rate of cell turnover tissues (like brain) it is low and in high turnover rate tissues (like blood) it is high

Question 18

What is a stem cell niche?

Answer 18

A special supportive micro-environment where tissue specific stem cells are maintained

Question 19

What are stem cell niches influenced by?

Answer 19

Neighbouring niche cells, secreted soluble signalling factors, physical parameters and environmental signals

Question 20

What are the main factors in stem cell niches?

Answer 20

• secreted factors
• inflammation and scarring
• extracellular matrix
• physical factors
• hypoxia and metabolism
• cellular components

Question 21

Where do blood cells come from (dependant on the maturity of the human)

Answer 21

Made in embryonic structures until week 20 when they originate from the bone marrow

Question 22

What is a hematopoietic stem cell?

Answer 22

Multipotent stem cells anchored to fibroblast-like osteoblasts or the marrow of long bones

Question 23

What do hematopoietic stem cells produce?

Answer 23

All blood cells and some immune system cells

Question 24

What are mesenchymal stem cells?

Answer 24

Stromatolites cells found in bone marrow and other organs. They’re poorly defined and heterogenous.

Question 25

Do mesenchymal stem cells self renew?

Answer 25

No

Question 26

What do mesenchymal stem cells produce?

Answer 26

Chondryocyctes, osteoblasts, myocytes and adipocytes

Question 27

What is a chondrocyte?

Answer 27

Cartilage cell

Question 28

What is an osteoblast?

Answer 28

Bone cell

Question 29

What is a myocyte?

Answer 29

Muscle cells

Question 30

What are progenitors?

Answer 30

Oligopotent cells only found in the myeloid or lymphoid lineage

Question 31

Can progenitors replicate indefinitely?

Answer 31

No, only a limited number of times

Question 32

What helps to determine how a cell differentiates?

Answer 32

The type and number of proteins

Question 33

What allows the analysation of the transcription profile of each cell?

Answer 33

RNA sequencing and microassays

Question 34

How do TFs affect gene expression?

Answer 34

They bind to regulatory regions of genes and affect its expression by switching it on or off

Question 35

Where are the two places TFs can be?

Answer 35

Differentiation of stem cells and some are tissue specific

Question 36

What is a basal transcriptions factor?

Answer 36

A TF necessary for the RNA polymerase to function at the site of transcription in eukaryotes

Question 37

What is considered the most basic set of proteins needed to activate a gene for expression?

Answer 37

Basal TFs

Question 38

Where do basal TFs bind to activate transcription?

Answer 38

The 5’ region of DNA

Question 39

How do specific TFs differentials regulate the expression of various genes?

Answer 39

By binding to the adhesive regions of DNA or the promoter regions

Question 40

What do specific TFs ensure?

Answer 40

The genes are expressed in the right cell at the right time in the right amount

Question 41

How do the different TFs know which genes to bind to?

Answer 41

The binding elements (motifs) in their promoters and enhancers

Question 42

What is a housekeeping gene?

Answer 42

Transcribed in all or nearly all cell types

Question 43

What is a luxury gene?

Answer 43

The specialised genes expressed in only some types of cells

Question 44

What is a pioneer factor?

Answer 44

TFs that can bind to condensed/ closed chromatin, remodel and initiate cell fate and differentiation

Question 45

What does a master regulator do?

Answer 45

Control the differentiation of the cell

Question 46

How common are pioneer factors in embryonic stem cells (and why)?

Answer 46

Very - needed to maintain their pluripotency

Question 47

Is DNA methylation heritable and reversible?

Answer 47

Yes

Question 48

What does DNA methylation result from?

Answer 48

External or environmental factors as part of the development programme

Question 49

Describe what DNA methylation does (and what it results in)

Answer 49

Covalent addition of the methyl group at the 5-Carbon of the cytosine ring resulting in 5-methyl-cytosine (5-mC)

Question 50

Where does 5-mc occur in somatic cells?

Answer 50

CpG sites

Question 51

Where does 5-mc occur in embryonic stem cells?

Answer 51

Can happen anywhere

Question 52

What is a CpG site?

Answer 52

A place where a cytosine is next to a guanine

Question 53

What does a de-novo methyltransferase do?

Answer 53

Methylate CpG pairs during differentiation

Question 54

What does a maintenance methyltransferase do?

Answer 54

Methylates the opposite strand

Question 55

What are the consequences of DNA methylation?

Answer 55

-methylation could increase folding and silencing

Question 56

In embryonic stem cells are the majority of CpG sites methylated?

Answer 56

Yes

Question 57

Where are globin genes expressed and what happens when they aren’t?

Answer 57

Red blood cell lineages- they’re methylated in all other cell types

Question 58

Give the steps of somatic cell nuclear transfer (SCNT)

Answer 58

- remove nucleus from a differentiated somatic cell and place it in a denucleated egg cell - new nucleus is reprogrammed by factors in the egg cytoplasm - the new egg behaves like a zygote (totipotent)

Question 59

What is an induced pluripotent stem cell (iPSc)?

Answer 59

Pluripotent stem cells artificially produced from somatic cells

Question 60

What is yamanakas cocktail and when is it used?

Answer 60

The four transcription factors iPScs are exposed to

Question 61

What are iPScs used for?

Answer 61

Gene therapy Model disease and drug screening Regenerative medicine/ cell transplantation