[W9] Life and Death of cells and organisms Flashcards
(30 cards)
What are the main factors affecting cell lifespan and ageing?
Telomere length, DNA damage/repair, energy metabolism, signalling (Insulin/IGF, PI3K, Tor, Sirtuins), and autophagy.
What are post-mitotic cells?
Cells that no longer divide after maturation, such as neurons and red blood cells.
Give an example of continuously dividing cells.
Stem cells in the intestine or bone marrow.
What are quiescent cells?
Cells that are usually inactive but can divide when triggered, e.g., liver cells.
What limits the number of times primary human cells divide?
Telomere shortening and donor age.
What is the role of telomerase in cell lifespan?
It maintains telomere length and allows more divisions; low activity limits division.
What is hTERT and its relevance in cancer?
Human telomerase reverse transcriptase; active in most cancers, promoting unlimited growth.
What is a cell line?
An immortalised cell population that can grow indefinitely in culture.
What is transformation in cells?
When cells gain cancer-like properties, losing growth control (e.g., anchorage independence).
What types of DNA damage affect single strands?
Base damage, mismatches, and nucleotide distortions.
What are the main single-strand repair mechanisms?
Base excision repair (BER), mismatch repair (MMR), and nucleotide excision repair (NER).
What causes thymine dimers and how are they repaired?
UV radiation causes them; repaired by nucleotide excision repair.
What disease is associated with defective NER?
Xeroderma pigmentosum – increased risk of early skin cancer.
What causes double-strand DNA breaks?
Ionising radiation and some chemotherapy drugs.
What are the main repair methods for double-strand breaks?
Homologous recombination (accurate) and non-homologous end joining (error-prone).
How does CRISPR/Cas9 use DNA repair mechanisms?
It introduces breaks that are repaired by NHEJ or homologous recombination to edit genes.
What role do BRCA genes play in DNA repair?
They act as scaffolds for assembling DNA repair complexes.
How do replication errors contribute to ageing?
Errors, if uncorrected, accumulate and damage the genome.
What enzyme helps reduce replication errors?
DNA polymerase δ via proofreading activity.
What is deamination and why is it a problem?
Conversion of cytosine to uracil or 5-methylcytosine to thymine; causes mutations if unrepaired.
How does mitochondrial function change with age?
ATP production efficiency declines, and ROS production increases, causing damage.
What are sirtuins?
NAD⁺-dependent deacetylases involved in stress resistance and energy regulation (e.g., SIRT1).
What is the role of mTOR in ageing?
Senses nutrient levels; its inhibition is linked to lifespan extension.
How does insulin/IGF-1 signalling relate to ageing?
Reduced activity is associated with increased lifespan in several model organisms.
