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?

<p>It allows the cells to resume proliferation. (B)</p> Signup and view all the answers

Which statement regarding telomerase activity is true?

<p>Medium to low telomerase activity is found in adult tissues. (B)</p> Signup and view all the answers

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

<p>They protect chromosome ends from degradation. (D)</p> Signup and view all the answers

Which of the following describes telomerase?

<p>A ribonucleoprotein that elongates chromosome ends. (D)</p> Signup and view all the answers

What is the consequence of telomere attrition over time?

<p>Cell senescence and eventual loss of cellular function. (D)</p> Signup and view all the answers

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

<p>Adult hematopoietic stem cells. (B)</p> Signup and view all the answers

What is the end-replication problem?

<p>Inability to fully replicate the ends of linear chromosomes. (A)</p> Signup and view all the answers

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

<p>They can be used to study and treat genetic diseases. (A)</p> Signup and view all the answers

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

<p>Studying organ development and disease. (B)</p> Signup and view all the answers

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

<p>Adult stem cells can only differentiate into specific cell types. (B)</p> Signup and view all the answers

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

<p>Telomeres shorten with age, affecting cell replication. (A)</p> Signup and view all the answers

What is the role of telomerase in cellular aging?

<p>Telomerase prevents the shortening of telomeres during cell division. (C)</p> Signup and view all the answers

What happens when telomeres become critically short?

<p>Cells undergo permanent growth arrest. (A)</p> Signup and view all the answers

Which of the following components directly contributes to telomere replication?

<p>Ribonucleoprotein (C)</p> Signup and view all the answers

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

<p>Increased levels of DNA polymerase. (B)</p> Signup and view all the answers

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

<p>Replication occurs in short segments known as Okazaki fragments. (C)</p> Signup and view all the answers

What characteristic primarily defines telomeres?

<p>Composed of repetitive DNA sequences. (C)</p> Signup and view all the answers

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

<p>It recognized the role of telomerase in aging and cancer. (A)</p> Signup and view all the answers

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

<p>Increased incidence of diskersatosis congenita-like phenotypes (D)</p> Signup and view all the answers

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

<p>Extended lifespan with a higher chance of developing cancer (C)</p> Signup and view all the answers

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

<p>Extensive telomere length variation (D)</p> Signup and view all the answers

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

<p>Promotion of stem cell activity and tissue regeneration (A)</p> Signup and view all the answers

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

<p>Impaired stem cell activity and tissue decline (B)</p> Signup and view all the answers

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

<p>Defective closure of the neural tube (C)</p> Signup and view all the answers

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

<p>Telomere length influences aging, but is not the only factor. (C)</p> Signup and view all the answers

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

<p>Decreased sperm quality and quantity (C)</p> Signup and view all the answers

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

<p>Mice become susceptible to obesity and diabetes. (D)</p> Signup and view all the answers

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

<p>They accumulate mutations due to their long lifespan and proliferative nature. (D)</p> Signup and view all the answers

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

<p>It results in uncontrolled proliferation. (C)</p> Signup and view all the answers

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

<p>Gene targeting via CRISPR/Cas9 (B)</p> Signup and view all the answers

What role do cancer stem cells play in tumor formation?

<p>They rebuild the tumor. (A)</p> Signup and view all the answers

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

<p>They can demonstrate gene function through observable traits. (A)</p> Signup and view all the answers

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

<p>Both quiescence and activation signals are disturbed. (B)</p> Signup and view all the answers

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

<p>To introduce gene modifications in models. (B)</p> Signup and view all the answers

Flashcards

Telomeres

The ends of linear chromosomes are protected by specialized DNA sequences called telomeres. These sequences are repetitive and non-coding, preventing the loss of genetic information during DNA replication.

End Replication Problem

The inability of DNA polymerase to fully replicate the ends of linear chromosomes due to the need for a primer.

Telomerase

A specialized enzyme that adds repetitive DNA sequences to the ends of chromosomes, preventing the loss of genetic material during replication.

Cell Senescence

A state of permanent cell cycle arrest. Cells enter senescence when they reach a certain age or experience stress.

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Telomere Attrition

The gradual shortening of telomeres with each cell division, leading to cell senescence.

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Adult Stem Cells

Stem cells that reside in specific tissues and can differentiate into specialized cell types for that tissue.

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Embryonic Stem Cells

Stem cells derived from embryos, capable of differentiating into any cell type in the body.

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Induced Pluripotent Stem Cells (iPS Cells)

Cells generated by reprogramming adult cells to an embryonic-like state, capable of developing into various cell types.

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Aging

The gradual decline in physiological function over time, ultimately leading to death.

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Genetic Component of Aging

The genetic component of aging that determines telomere length and other factors contributing to lifespan.

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Environmental Component of Aging

Environmental factors that influence aging, such as diet, exercise, stress, and exposure to toxins.

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Hayflick Limit

A phenomenon where cells stop dividing after a certain number of divisions due to critically short telomeres.

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Shutting Down Telomerase

A key mechanism of tumor suppression, preventing uncontrolled cell growth by inducing cell senescence and limiting telomere length.

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What are stem cells?

Stem cells are undifferentiated cells that have the ability to divide and differentiate into specialized cell types. They are essential for tissue repair and regeneration throughout life.

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What are hematopoietic stem cells?

Hematopoietic stem cells (HSCs) are a type of stem cell found in bone marrow that give rise to all blood cells, including red blood cells, white blood cells, and platelets.

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What is gene targeting?

Gene targeting refers to the process of altering the genetic makeup of an organism by precisely modifying specific genes. This can be used to study gene function and develop disease models.

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What is a gene knockout experiment?

A knockout (KO) experiment involves disabling or deleting a specific gene in an organism to study its function and potential role in diseases. For example, knocking out the leptin gene in mice has been used to investigate the role of leptin in regulating appetite and metabolism.

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What are cancer stem cells?

Cancer stem cells are a rare population of cells within tumors that have the potential to self-renew and give rise to all other cancer cells. They are thought to contribute to the recurrence and spread of cancer.

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How are stem cell regulatory signals linked to cancer?

Stem cell regulatory signals are pathways that control the growth, differentiation, and self-renewal of stem cells. Disruptions in these pathways can contribute to cancer development by promoting uncontrolled cell growth and inhibiting differentiation.

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What is the biology of aging?

The biology of aging is a complex field that investigates the processes involved in the decline of biological function over time. It encompasses aspects like genetics, cellular changes, and environmental factors.

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What determines how long we live?

The lifespan of an organism is determined by a complex interplay of genetic and environmental factors. While there is a genetic component, lifestyle choices and environmental influences also play a significant role in determining how long we live.

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Heterochronic Parabiosis

Connecting the blood circulation of two organisms, one young and one old, to study the effects of a youthful or aged systemic environment on stem cells.

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Altered Cell-Cell Communication Signals

Changes in the signaling molecules that regulate cell communication, contributing to aging and stem cell decline.

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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.

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