The theory of ageing

Question 1

Dietary restriction and the suppression of particular chemicals appear to slow ageing. True or false?

Answer 1

True.

Question 2

In C. elegans, a mutation in what gene has been shown to slow ageing?

Answer 2

Daf-2

Question 3

In drosophila, a mutation in what gene has been shown to slow ageing?

Answer 3

Chico

Question 4

In mice, a mutation in what gene has been shown to slow ageing?

Answer 4

lgf-1

Question 5

Define ageing.

Answer 5

Refers to the passing of time and its effect on something. Can have both negative or positive connotations.

Question 6

Define senescence.

Answer 6

The decline of fitness in an individual due to increasing age that has caused internal deterioration.

Question 7

Define gerontology.

Answer 7

The study of the biological, psychological and social effects of ageing.

Question 8

Define geriatrics.

Answer 8

The branch of medicine that deals with age-related illness.

Question 9

The study of demographic senescence is interested in which factors?

Answer 9

Things like mean and median lifespan of a population.

Question 10

The oldest human in the world was Madame Jeanne Calment, who died in 1993 at the age of?

Answer 10

122.

Question 11

As you age the probability of dying increases. What kind of growth curve would this produce on a graph?

Answer 11

Exponential.

Question 12

‘Testosterone dementia’ causes an elevated number of deaths in the 16-20 age bracket. What does this refer to?

Answer 12

Deaths in young people from stupid behaviour or suicide.

Question 13

Is ‘testosterone dementia’ higher in males or females?

Answer 13

Males.

Question 14

Define the Gompertz Law of 1825.

Answer 14

Mortality increases exponentially with age.

Question 15

Define the Gompertz parameter.

Answer 15

A slope of log mortality against age.

Question 16

What does MRTD stand for?

Answer 16

Mortality rate doubling time.

Question 17

What is the MTRD for humans?

Answer 17

8 years.

Question 18

Why have diseases like Huntingdon’s, which is highly damaging, not been removed by natural selection?

Answer 18

Because they have late onset - for example the average age of onset for Huntingdon’s is 35.5years. The selection pressure to remove them is low as they do not affect an individual during development or at prime reproductive age.

Question 19

What is the basic principle regarding mutation and age?

Answer 19

Mutations with deleterious effects later in life are subject to weaker selection pressures.

Question 20

Define intrinsic mortality.

Answer 20

Even without ageing, most species have an intrinsic mortality due to predation, starvation etc.

Question 21

What is the mutation accumulation theory?

Answer 21

Mutations that are active early in life have a strong selective pressure and are removed. Mutations acting later in life have a weak selective pressure and are allowed to accumulate. This accumulation causes ageing.

Question 22

Define the antagonistic pleiotropy theory.

Answer 22

Some mutations are beneficial early on in life, but then become deleterious later on. These mutations are tolerated by natural selection as they aid survival in youth, and more organisms are likely to survive during youth than to survive to old age.

Question 23

What is another name for the antagonistic pleiotropy theory?

Answer 23

The trade-off theory.

Question 24

In general which is more widely accepted, the mutation accumulation or antagonistic pleiotropy theory?

Answer 24

Antagonistic pleiotropy.

Question 25

There are 3 main theories regarding the mechanism of ageing. What are they?

Answer 25

1. The Rate-of-living theory (ROL)
2. Oxidative damage
3. Cellular theory, i.e. the Hayflick limit

Question 26

Explain the ROL theory.

Answer 26

The faster an organism’s metabolism, the shorter its lifespan. Larger animals have slower metabolisms and thus outlive smaller ones.

Question 27

What evidence did Loeb and Northrop have for ROL theory?

Answer 27

Increasing temp. reduces drosophila lifespan.

Question 28

What evidence did Raymond and Pearl 1928 have for ROL theory?

Answer 28

Biochemical reactions occur at higher temperatures, thus rate of metabolism is crucial.

Question 29

Define life energy potential (LEP).

Answer 29

Lifetime energy turnover per kilogram.

Question 30

In ROL theory, LEP decreases with age. True or false?

Answer 30

False - it is constant.

Question 31

Who came up with ROL theory and when?

Answer 31

Max Rubner in 1908.

Question 32

What is the oxidative damage theory of ageing?

Answer 32

Ageing results from molecular damage by free radicals produced during metabolism.

Question 33

Define a free radical.

Answer 33

A species with an unpaired electron, highly reactive.

Question 34

A superoxide or oxygen free radical (O2-) can react with DNA only. True or false?

Answer 34

False - it reacts with DNA, lipids and proteins.

Question 35

Which organelle generates superoxide radicals?

Answer 35

Mitochondria during aerobic respiration.

Question 36

There is a link between ROL and oxidative damage. What is it?

Answer 36

Higher levels of oxidative damage are produced in faster metabolism, which requires higher temperatures.

Question 37

Oxidative damage theory is widely accepted. True or false?

Answer 37

False - it is highly controversial.

Question 38

When was the Hayflick limit hypothesised?

Answer 38

1961.

Question 39

What is the Hayflick limit?

Answer 39

The number of times a (human) cell can divide before division stops. This is due to a shortening of the telomeres with each round of division.

Question 40

In human cells, how many rounds of division can occur before the cell stops dividing?

Answer 40

Approx. 50, +/-10.

Question 41

Define replicative senescence.

Answer 41

A limitation to the number of times a cell can divide.