Theories of Ageing

Question 1

Theories of WHY we age:
Wear and Tear - What is it?

Adaptive Evolutionary - What is it?

Non-adaptive Evolutionary - What is Mutation accumulation and Antagonistic Pleiotropic genes?

Disposable Soma theory - What is it?

Answer 1

• We are a machine that wears out
• Ageing selectively advantageous to a species
• • Mutation accumulation - Genes expressed after reproduction are lost from evolutionary control
  • Antagonistic Pleiotropic genes - Genes have an Early positive effect and a Late negative effect
• Organism is a machine that transfers free energy to progeny
  o Species specific longevity as they prioritise different thing - e.g. some prioritise fertility while others prioritise maintenance

Question 2

Theories of HOW we age:
System-Level Theories - What is the Neuroendocrine theory?

Cellular-Level Theories - What are the 4 aspects of it?

Genomic Stability - What are the 5 aspects of it?

Answer 2

• Functional decrease in neurons and associated hormones (Decreased HPA-axis)
• • Wear and Tear - Higher basal metabolic rate leads to shorter lifespan
  • Crosslink formation - Biological molecules develop cross links over time, affecting its physical and chemical properties
  • Heat Shock proteins - Produced at times of cell stress; decreased production of it with age, leading to decreased ability to cope with stress
  • Hayflick Phenomena - Biological clock; Fibroblasts in culture divide a set number of times before stopping, which is due to Telomere depletion
  o Telomeres shorten with each division
  o HeLa cell line (Breast carcinoma) has unlimited division
• • Error catastrophe - Accumulation of errors in transcription and translation leads to ageing
  • Somatic mutation - Unimportant due to low occurrence rate and DNA repair
  • Free Radical Theory - Highly reactive chemical compounds from reactions that damage DNA; there are many enzymes that protect the cells
  • Mitochondrial Theory - Mitochondrial DNA is damaged due to O2 radicals; it has no Protein coat for protection
  • Cell Senescence - Triggered by DNA damage, leading to Growth Arrest and altered gene expression; Upregulation of degrading enzymes and stimulation of pre-malignant cell growth