Lecture 24 Review

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Questions and Answers

What happens to cells without telomerase once their telomeres reach critically short lengths?

They enter a state of senescence. (correct)

They undergo apoptosis.

They transform into cancer cells.

They continue to proliferate indefinitely.

How is cellular senescence related to cancer?

It has no effect on cancer.

It serves as a tumor-suppressing mechanism. (correct)

It only affects immune cells and does not influence cancer.

It promotes cancer development.

What is the 'Hayflick limit'?

The point at which cells become cancerous.

The maximum number of times a cell can divide before senescence. (correct)

The minimum telomere length required for division.

The total lifespan of a cell after restoring telomerase activity.

What is the effect of restoring telomerase activity in senescent cells?

It allows the cells to resume proliferation. Signup and view all the answers

Which statement regarding telomerase activity is true?

Medium to low telomerase activity is found in adult tissues. Signup and view all the answers

What is the primary function of telomeres in relation to DNA replication?

They protect chromosome ends from degradation. Signup and view all the answers

Which of the following describes telomerase?

A ribonucleoprotein that elongates chromosome ends. Signup and view all the answers

What is the consequence of telomere attrition over time?

Cell senescence and eventual loss of cellular function. Signup and view all the answers

Which type of stem cells are primarily used for clinical applications today?

Adult hematopoietic stem cells. Signup and view all the answers

What is the end-replication problem?

Inability to fully replicate the ends of linear chromosomes. Signup and view all the answers

Which of the following best describes the role of iPS cells?

They can be used to study and treat genetic diseases. Signup and view all the answers

What is a potential application of organoids derived from cultured stem cells?

Studying organ development and disease. Signup and view all the answers

Which of the following statements is true regarding stem cell therapies?

Adult stem cells can only differentiate into specific cell types. Signup and view all the answers

What is the significance of telomeres in the context of aging?

Telomeres shorten with age, affecting cell replication. Signup and view all the answers

What is the role of telomerase in cellular aging?

Telomerase prevents the shortening of telomeres during cell division. Signup and view all the answers

What happens when telomeres become critically short?

Cells undergo permanent growth arrest. Signup and view all the answers

Which of the following components directly contributes to telomere replication?

Ribonucleoprotein Signup and view all the answers

Which factor is NOT related to the decline of telomere length?

Increased levels of DNA polymerase. Signup and view all the answers

What challenges are associated with the lagging strand during DNA replication?

Replication occurs in short segments known as Okazaki fragments. Signup and view all the answers

What characteristic primarily defines telomeres?

Composed of repetitive DNA sequences. Signup and view all the answers

Which statement about the Nobel Prize for Medicine in 2009 is accurate?

It recognized the role of telomerase in aging and cancer. Signup and view all the answers

What is one consequence of TERC knockout in late generations of mice?

Increased incidence of diskersatosis congenita-like phenotypes Signup and view all the answers

What impact does over-expression of TERT protein have on mice?

Extended lifespan with a higher chance of developing cancer Signup and view all the answers

Which of the following is NOT proposed as a factor contributing to organismal aging?

Extensive telomere length variation Signup and view all the answers

What is the effect of 'heterochronic parabiosis' on aged mice?

Promotion of stem cell activity and tissue regeneration Signup and view all the answers

What consequence does exposing young mice to an aged systemic environment have?

Impaired stem cell activity and tissue decline Signup and view all the answers

Which phenotype is associated with defective neural stem cells (NSC) in TERC knockout mice?

Defective closure of the neural tube Signup and view all the answers

Which statement best describes the relationship between telomere length and aging?

Telomere length influences aging, but is not the only factor. Signup and view all the answers

What is a notable sign of infertility observed in late generations of TERC knockout mice?

Decreased sperm quality and quantity Signup and view all the answers

What is a consequence of the leptin knockout experiment in mice?

Mice become susceptible to obesity and diabetes. Signup and view all the answers

Why are stem cells thought to be a possible origin for many cancers?

They accumulate mutations due to their long lifespan and proliferative nature. Signup and view all the answers

What impact does the inactivation of quiescence signals have on stem cells in cancer?

It results in uncontrolled proliferation. Signup and view all the answers

What technique is exemplified by the introduction of specific gene modifications in embryos?

Gene targeting via CRISPR/Cas9 Signup and view all the answers

What role do cancer stem cells play in tumor formation?

They rebuild the tumor. Signup and view all the answers

What is a notable effect of gene knockout experiments, such as those involving leptin?

They can demonstrate gene function through observable traits. Signup and view all the answers

How do regulatory signals differ in stem cells associated with cancer compared to normal stem cells?

Both quiescence and activation signals are disturbed. Signup and view all the answers

How have embryonic stem cells been utilized in research related to certain genetic conditions?

To introduce gene modifications in models. Signup and view all the answers

Study Notes

Telomeres, Telomerase, and Aging

Telomeres are heterochromatic DNA sequences that are repetitive
Telomeres are located at the ends of chromosomes
Telomeres are crucial for protecting chromosomes from degradation and fusion
The end-replication problem is a key challenge in DNA replication
Telomerase is a ribonucleoprotein that helps elongate chromosome ends
Telomerase is essential for maintaining telomere length
Telomere attrition leads to cell senescence, which is a type of cellular aging
Cell senescence is a tumour-suppressing mechanism
Telomere length varies among species, individuals, and cell types
Telomere length shortens with age.

Stem Cells and Aging

Adult stem cells, as well as embryonic stem cells, and induced pluripotent stem (iPS) cells play an important role in organismal aging.
Stem cell renewal and pro-cancer pathways are interconnected
Stem cells are likely the source of many cancers, due to their long lifespan and inherent pro-liferative nature.
Many factors influence the regulation of stem cells, and disruption to these factors can result in diseases/cancers.

iPS Cells

iPS cells can be produced from adult cells and can be utilized to study and treat genetic diseases
iPS cells can act as a source for creating organoids

Organoids

Organoids can be obtained from various tissue types, such as crypts or epithelial mini-guts
Organoids are useful for experimental research, diagnostics, and regenerative medicine.

Adult Hematopoietic Stem Cells

Adult hematopoietic stem cells are frequently utilized in clinical settings
Treatments involve chemotherapy or radiation to kill cancer, which also damages hematopoietic cells
Strong chemotherapy or radiation is used to kill cancerous cells, but also destroys healthy hematopoietic cells.

Basic Science Applications of ESCs

Specific gene modifications are introduced to mice using embryonic stem (ES) cells, which allowed scientists to identify the precise function of certain genes and their role in cellular processes.
This work opened the door for further understanding and eventually led to the 2007 Nobel Prize in Physiology or Medicine.

Gene Knockout Experiment (Leptin)

A gene knockout experiment on leptin knockout mice demonstrated the role of leptin in regulating body fat and hunger; it also resulted in obesity and susceptibility to diabetes.

Nine Proposed Hallmarks of Organismal Aging

Nine characteristics of aging are presented
The hallmarks include genomic instability, telomere attrition, epigenetic alterations, proteostasis loss, nutrient sensing alterations, and more. . These characteristics influence each other, and their interplay is vital to our understanding of aging.

Interventions that Might Extend Human Healthspan

Clearance of senescent cells, and stem-cell-based therapies, are important steps towards extending human lifespan.
Multiple avenues of investigation exist to combat premature aging.

Telomere Replication

Telomere replication plays a crucial role in maintaining chromosome integrity and stability.

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Description

Explore the intricate roles of telomeres and stem cells in the aging process. This quiz delves into how telomeres protect chromosomes and the function of telomerase in cellular longevity. Additionally, understand the relationship between stem cells, aging, and cancer pathways.