November 23

November 23 - Biology 442 Developmental Biology Lecture 9...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Biology 442 Developmental Biology Lecture 9 Senescence
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Lecture outline I. Evolutionary hypotheses of aging: antagonistic pleiotropy and disposable soma II. Causes of senescence: 1. Cell division and the shortening of telomerases 2. Oxidative damage 3. Calorie intake
Background image of page 2
Learning objectives for this class Explain theories of why aging occurs Explain the cellular causes for senescence and identify the ways in which they are interconnected Compare the function of the insulin pathway in regulating lifespan in different animals
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Definitions Senescence : time-related deterioration of the physiological functions necessary for survival and fitness Life span : maximum number of years a member of a species has been known to survive - Humans: 121 years - Tortoises and lake trout: ~ 150 years - Dog: 20 years - Fruit Fly: 3 months Life expectancy : length of time an individual from a given species can expect to live Life expectancy is not a function of a species but rather of a population - England, 1780s: life expectancy = 35 - Massachussetts, 1780s: life expectancy = 28
Background image of page 4
Senescence in humans is a relatively recent occurrence The US currently ranks 24th in the world for life expectancy Since life expectancy has increased significantly over the century, the phenomenon of senescence is a recent occurrence Survival curve for US females In 1900: 50 % of women dead by age 58 In 1980: 50 % of women dead by age 81
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Modifiable behavioral risk factors are leading causes of mortality in the United States. Senescence is not the leading cause of death in the US
Background image of page 6
Senescence is not the leading cause of death in the US Nearly half the deaths in 2000 are caused by factors unrelated to age
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Evolutionary hypotheses of aging Multiple genes exist, each with two or more alleles that show antagonistic pleiotropy - One allele promotes reproductive success in life, but with a price to pay later in early senescence - The other allele of the same gene has the opposite effect Antagonistic pleiotropy hypothesis (Medawar and Williams, 1950s) According to the antagonistic pleiotropy theory, natural selection favors genes conferring short-term benefits to the organism at the cost of deterioration in later life - Example: production of sex hormones in humans: Confer enhanced production of androgen in men after puberty is beneficial for the production of strong bones, muscle and sperm but later in life, androgen may contribute to hyperplasia or cancer of the prostate gland
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 26

November 23 - Biology 442 Developmental Biology Lecture 9...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online