LIFESCI 3C03 Chapter Notes - Chapter 6: Kin Selection, Life Insurance, Meiosis

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Ecology Selfish Gene Reading Chapter 6
Genemanship
The goal of selfish genes is to become more numerous in the gene pool
A gene might be able to assist replicas of itself that are sitting in other bodies
Albinism
- Recessive trait
- 1/20,000 people require two genes for albinism to show the phenotype
- 1/70 people who have two copies of the albinism allele are not albinos
- If the albino gene could make one of its bodies save the lives of 10 of its bodies, altruism
would ultimately be beneficial
If a gene causes altruistic behaviour toward other individuals who share the gene, it will be
perpetuated in the population.
- The gee does’t at to help other idiiduals, ut if it odes for altruisti ehaiour,
it will be passed on and its future carriers will be altruistic as well, and so on.
- This gene would have multiple effects:
1. Confer a trait
2. Confer a tendency to be selectively altruistic toward other individuals who share the
trait
This is a theoretical possibility, but not likely (Green Beard Altruism Effect)
The possessor of an altruistic gene may be recognized by a distinctive feature (e.g. green beard)
or simply by observation of the individual performing altruistic behaviours.
Kin have a greater than average chance of sharing genes
- Siblings are 50% related in that if you had 100 brothers and sisters, approximately 50 of
them would contain any particular rare gene you contain
- An index of relatedness expresses the chance of a gene being shared between two
relatives
Between siblings: about 50% (meiosis can lead to higher or lower)
Between child and parent: exactly 50%
- Generation distance is the number of relatives that separate individuals from one
another
E.g. an individual to their cousin: individual, mother/father, aunt/uncle, cousin
creates a relationship distance of 4
- Relatedness = (1/2)generation distance
E.g. an individual to their cousin: relatedness = (1/2)4 = 1/8
The minimum requirement for a suicidal altruistic gene to be successful is that it should save
more than two siblings (or children or parents), or more than four half-siblings (or uncles, aunts,
nephews, nieces, grandparents, grandchildren), or more than eight first cousins, etc.
- In gene selection terms, a gene for big sister altruistic behaviour should have just as
good a chance of spreading through the population as a gene for parental altruism.
Kin selection accounts for within-family altruism.
- The distinction between family and non-family is a matter of mathematical probability
- A special consequence of gene selection
Expectation of life must be accounted for within calculations of altruism
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