Biology 1002B: Cycle 8 And Cycle 9
Final Test Questions and Answers
2025-2026 Updated.
What is the role of telomerase in telomere length? Where is telomerase active in ? - Answer
- the telomere length protects the DNA from shortening to the point it affects the gene
- telomerase active cells restores the telomere length preventing it from reaching the hayflick
limit
- telomerase is active in cancer cells since cancer cells need to divide fast and cannot be limited
by the hayflick limit, it is also active in stem cells since stem cells need to differentiate into diff
tissue types, it is also active in early embryogenesis since it requires a high capacity for cell
division and needs to differentiate into different tissues
What is the hayflick limit? - Answer Cells divide, causing a shortening of DNA and it
eventually reaches a point where it affects the gene, causing cell senescence (where they stop
dividing)
Explain what "unused genes are not destroyed and retain the potential for being expressed"
means - Answer - some cells are not destroyed but they retain the potential to be expressed
when activated
- for example, in cancer cells, telomerase is activated
Describe how gene expression is controlled in the transcriptional stage, key regulators and what
binds to them? How would they work? - Answer - key regulators include the promoter, and
regulatory sites
- tissue specific transcription factors (bind to promoter) and tissue specific regulatory proteins
(bind to regulatory sites) act as activators and repressors for the transcription of a gene
- gene regulatory proteins also bind to regulatory sites to control the rate of transcription
- For example, a heart specific gene would have gene regulatory proteins activate and repress
the expression in the liver
Describe how transcription factors are regulated by signal transduction pathways - Answer -
they are tightly regulated by molecules that are upstream of the transcription factors
- external stimulus is received by the cell, receptors will then be triggered and induce a signal
transduction pathway
- the transduction pathway is where receptors activate a sreries of things!! which forms the
transcription factors and induces transcription
, At what stages can we control gene expression? Which stage is most important? - Answer -
transcription
- post transcription
- translation
- post translation
- transcription stage is most important cuz why would we want to spend energy transcribing and
translating if we are going to be inhibiting the proteins function anyways?
What is spatial and temporal regulation? - Answer - spatial is where in the cell/body that
specific combination of transcription factors are present
- temporal is when the transcription factors are activated, this is controlled by signal
transduction pathways
- they help regulate gene expression by determining what cell type a stem cell can give rise to
What are motifs on transcription factors? - Answer - they are a series of amino acids that
make the physical interaction w the dna
What are the four types of stem cells? - Answer 1. embryonic stem cells (blastocyst inner
mass)
2. Somatic (adult) stem cells
3. IPS
4. Umbilical cord stem cells (cord blood, can be used for stem cell therapy in the future)
What are the levels of potency in stem cells? - Answer - Totipotent: can differentiate into any
cell (embyronic and extraembryonic - umbilical cord), can form an entire viable organism, only
the zygote is totipotent
- Pluripotent: can form nearly all cells except for extraembryonic/embryonic inner mass cells)
- multipotent: can differentiate into a family of cells (closely related to each other)
- Unipotent: can only produce on cell type (epidermal/skin stem cells)
Whats different between a unipotent stem cell and a somatic cell? - Answer - unipotent cells
can self renew, meaning that they never reach the hayflick limit (since telomerase is active) but
somatic cells eventually reach the hayflick limit and enter irreversible cell arrest
Whats iffy abt studying embryonic stem cells? - Answer - ethical issues since its taking the
inner mass of the blastocyst (human embryo)
How do stem cells divide? - Answer - stem cells hibernate in the niche of tissue and come
out to divide when neighbouring cells send signals
Final Test Questions and Answers
2025-2026 Updated.
What is the role of telomerase in telomere length? Where is telomerase active in ? - Answer
- the telomere length protects the DNA from shortening to the point it affects the gene
- telomerase active cells restores the telomere length preventing it from reaching the hayflick
limit
- telomerase is active in cancer cells since cancer cells need to divide fast and cannot be limited
by the hayflick limit, it is also active in stem cells since stem cells need to differentiate into diff
tissue types, it is also active in early embryogenesis since it requires a high capacity for cell
division and needs to differentiate into different tissues
What is the hayflick limit? - Answer Cells divide, causing a shortening of DNA and it
eventually reaches a point where it affects the gene, causing cell senescence (where they stop
dividing)
Explain what "unused genes are not destroyed and retain the potential for being expressed"
means - Answer - some cells are not destroyed but they retain the potential to be expressed
when activated
- for example, in cancer cells, telomerase is activated
Describe how gene expression is controlled in the transcriptional stage, key regulators and what
binds to them? How would they work? - Answer - key regulators include the promoter, and
regulatory sites
- tissue specific transcription factors (bind to promoter) and tissue specific regulatory proteins
(bind to regulatory sites) act as activators and repressors for the transcription of a gene
- gene regulatory proteins also bind to regulatory sites to control the rate of transcription
- For example, a heart specific gene would have gene regulatory proteins activate and repress
the expression in the liver
Describe how transcription factors are regulated by signal transduction pathways - Answer -
they are tightly regulated by molecules that are upstream of the transcription factors
- external stimulus is received by the cell, receptors will then be triggered and induce a signal
transduction pathway
- the transduction pathway is where receptors activate a sreries of things!! which forms the
transcription factors and induces transcription
, At what stages can we control gene expression? Which stage is most important? - Answer -
transcription
- post transcription
- translation
- post translation
- transcription stage is most important cuz why would we want to spend energy transcribing and
translating if we are going to be inhibiting the proteins function anyways?
What is spatial and temporal regulation? - Answer - spatial is where in the cell/body that
specific combination of transcription factors are present
- temporal is when the transcription factors are activated, this is controlled by signal
transduction pathways
- they help regulate gene expression by determining what cell type a stem cell can give rise to
What are motifs on transcription factors? - Answer - they are a series of amino acids that
make the physical interaction w the dna
What are the four types of stem cells? - Answer 1. embryonic stem cells (blastocyst inner
mass)
2. Somatic (adult) stem cells
3. IPS
4. Umbilical cord stem cells (cord blood, can be used for stem cell therapy in the future)
What are the levels of potency in stem cells? - Answer - Totipotent: can differentiate into any
cell (embyronic and extraembryonic - umbilical cord), can form an entire viable organism, only
the zygote is totipotent
- Pluripotent: can form nearly all cells except for extraembryonic/embryonic inner mass cells)
- multipotent: can differentiate into a family of cells (closely related to each other)
- Unipotent: can only produce on cell type (epidermal/skin stem cells)
Whats different between a unipotent stem cell and a somatic cell? - Answer - unipotent cells
can self renew, meaning that they never reach the hayflick limit (since telomerase is active) but
somatic cells eventually reach the hayflick limit and enter irreversible cell arrest
Whats iffy abt studying embryonic stem cells? - Answer - ethical issues since its taking the
inner mass of the blastocyst (human embryo)
How do stem cells divide? - Answer - stem cells hibernate in the niche of tissue and come
out to divide when neighbouring cells send signals
