Lecture 3 - Why we age?

• Several factors influence the Aging of an organism

  1. Telomeres
  2. Cell Senescence
  3. Genetic Inheritance
  4. Caloric Intake
  5. Epigenetics
• • Every chromosome has a portion of DNA at its ends that protect the genetic coding information from being lost, from errors and mutations during replication. Called Telomeres
• • The Telomeres are a repeating sequence of DNA
• • Every time a cell goes through mitosis the chromosome’s Telomeres will become a tiny bit shorter than those of the parent cell’s, but the coding regions of DNA remain.
• • Thus a small portion of the Telomeres section is lost in each division.
• • After several divisions the telomere may become so short that it can no longer protect the chromosome’s genes.
• • During this time genetic DNA is lost and the cell may lose information on how to conduct important functions. 
• • This is the period in a cell’s life when it has lost its ability to conduct normal function and is an “aging cell”. This time is called Cell Senescence
• • Each cell in your body has a maximum number of mitotic divisions is can undergo ~ Hayflick Limit
• • Various cell types have a different rate at reaching their Hayflick Limit
• • Cancer cells have the ability to create their own telomerase (enzyme that makes telomere ends on chromosomes)
  • Thus have the ability to replicate indefinitely without their telomeres becoming damaged… thus form tumors
• • The genes we inherit from our parents also plays a role in our lifespan
• • Some genes are beneficial for metabolism or maintaining homeostasis in our bodies and some genes are harmful and can increase risk of disease or cancer.
• Genetic Inheritance

  • These genes are passed down generations
• Caloric Intake

  • We need calories to give us the energy we need to conduct our various bodily functions and maintain homeostasis inside our bodies.
• 1. Caloric Intake

  • However, lower calorie intake leads to a longer lifespan
• Caloric Intake

  • Higher amount of calories CAN stimulate the genes that increase our aging process
• • We are learning that what your grandparents did in their life and changes that occurred to their genome in terms of methyl groups and histones is passed down through the generations!
• • Epigenetics ~ Literally means above genetics
• Epigenetics

  • This looks at how your “life” can influence how much or whether certain genes are expressed… It doesn’t change your DNA
• Epigenetics

  • In general the position of Methyl groups and histones on your DNA molecule can determine which genes are expressed in a particular cell. This information can change in your lifetime.
• Epigenetics

  • It also studies how these changes can be passed down to your children or even your grandchildren.