Lecture 3: Basic Molecular Cell Biology 1

Question 1

a stem cell is a (relatively) primitive cell that is capable of:

Answer 1

• Self-renewal: making a copy of oneself
• Make a range of cell types (potency)
• convert to a range of different cell types (differentiation)

Question 2

The features of stem cells allow them to:

Answer 2

• build embryos, and tissues (development )

- Repair tissues (regeneration)

Question 3

All the processes of stem cells require cells to

Answer 3

receive and process information

Question 4

growth factors:

Answer 4

stimulate growth (increased cell size) by promoting synthesis and inhibiting degradation of macromolecules.

This requires signals - i.e. a method to get information into the cells and process it

Question 5

death factors:

Answer 5

promote apoptosis

–may be an active process

Question 6

Survival factors:

Answer 6

suppress apoptosis

–may be an active process

Question 7

animal cells require ______ to divide, grow & survive

Answer 7

extracellular signals

Question 8

information flow in cells:

Answer 8

-DNA (replication)
-RNA
-Protein (links back to all previous)
signals ions
Environment

Stem cells process this information to either, Self renew, Differentiate or Die by changing gene expression

Question 9

stem cells express genes that define it’s …

Answer 9

‘state’

These states are actively maintained by receiving external signals.

Question 10

external signals to stem cells can be:

Answer 10

• soluble ligands for receptors

- internally generated signals

Question 11

what components are needed to process signals?

Answer 11

Signalling:

• Signals
• Membrane
• Intracellular effectors

Gene expression:

• transcription factors
• -leads to state change (gene expression change)
• Histones Chromatin remodelling factors

Question 12

gene expression (stem cell to diff cell or another stem cell)

Answer 12

• to differentiate i.e. change cellular state
• you have to turn genes on & off AND lock those changes in
• i.e. chromatin has to be altered to allow or close down TRANSCRIPTION
• POST-TRANSCRIPTION the amount of a protein that is made can be controlled at many levels

Question 13

chromatic structure

Answer 13

• short region of DNA double helix
• “beads-on-a-string” form of chromatin
• 30-nm chromatin finer of packed nucleosomes
• interphase: extended scaffold-associated chromatin
• condensed scaffold-associated chromatin
• metaphase chromosome

Question 14

the building blocks of chromatin are

Answer 14

nucleosomes.

-nucleosomes can be covalently modified - these structural changes to chromatin affect gene expression.

Question 15

how do covalent modifications to nucleosomes affect gene expression

Answer 15

the chromatin becomes more or less condensed. This changes the accessibility to transcription factors

Question 16

which specific part of nucleosome are covalently modified

Answer 16

N-terminal lysine-rich tails of core histones project radially from the nucleosomal core

Question 17

heterochromatin means

Answer 17

‘closed’

Question 18

euchromatin =

Answer 18

‘open’

Question 19

methylation of DNA can block transcription by two distinct pathways

Answer 19

1) direct blocking of TFIID binding (TATA binding protein)

2) Recruitment of histone deacteylases

Question 20

Whats the TATA box?

Answer 20

the TATA box is a DNA sequence found in the promoter region of genes

Question 21

TFIID is a transcription factor which binds to

Answer 21

TATA box

Question 22

TATA box is the binding site of

Answer 22

1) general transcription factors (TFIID)
2) histones
binding of a transcription factor blocks the binding of a histone and vice versa

Question 23

control of transcription:by expressing specific proteins such as transcription factors in different cells types

Answer 23

-only a certain repertoire of genes are switched on

Question 24

control of transcription: chromatin condensed

Answer 24

Gene ‘off’

unravelled = gene ‘on’

Question 25

tissue-specific enhancers job

Answer 25

drive expression differently in different cell types and times

Question 26

Alternative RNA splicing

Answer 26

removal of introns but also potentially some of the axons. –> single gene codes for multiple proteins

Question 27

degradation of mRNA:

Answer 27

is a control of transcription.
siRNA (small interfering RNA) is the most commonly used RNA interference. siRNA is a synthetic RNA duplex designed to specifically target a particular mRNA for degradation.

Question 28

blockage of translation is

Answer 28

another way of controlling transcription

Question 29

miRNA

Answer 29

A microRNA (abbreviated miRNA) is a small non-coding RNA molecule that functions in RNA silencing and post-transcriptional regulation of gene expression.

Question 30

post-translation controls of gene expression

Answer 30

• Protein processing, transport.

- Proteasomes degrade ubiquitin-tagged proteins.

Question 31

degradation of a protein by a proteasome

Answer 31

Ubiquitin protein tags other proteins for destruction by proteasome.

1) protein to be degraded
2) Ubiquitin binds to protein = ubiquitinated protein
3) proteasome recognises & protein enters proteasome
4) proteasome and ubiquitin released to be recycled
5) final product = degraded protein (peptides)

Question 32

the choice cells make are governed at

Answer 32

lots of levels

Question 33

transcription and translation can be controlled by:

Answer 33

• Chromatin modifications (DNA methylation, Histone acetylation),
• cell specific TF’s,
• alternative splicing,
• degradation of mRNA, -blockage of translation,
• protein processing,
• transport,
• proteasome degradation

All converge to result in a particular expression level of proteins which define a cells state