Please enable JavaScript.
Coggle requires JavaScript to display documents.
L21 - Genetic Variance in Populations
Describe the influence of…
L21 - Genetic Variance in Populations
- Describe the influence of inbreeding on heterozygosity in populations
- Define the terms coefficient of relationship and coefficient of inbreeding and understand the correlation between them*
*15. Describe the three key principles of Darwinian evolution
- Describe the principle of Natural selection (Darwin) and that
different genotypes have different fitness
- Understand that variants can arise from different environments and adaptation
- Define the term “selective sweep”*
Variation from Mutation
Mutation Rate may be defined as; probability that one copy of an allele changes to another allelic form in a single generation.
=> Increase in frequency of a mutant allele will be the product of the mutation rate multiplied by the frequency of the non-mutant allele
Mutation isn't Sufficient to explain Allelic Frequency
Mutation is *one source of genetic variationHowever, mutation is too rare to explain
changes in allele frequencies of
populations**What other processes are acting?
- Migration
- Selection
- Non-random mating
- Random events*
Darwinian Evolution
Principle of selection
Some variants are more successful at
surviving and reproducing than other
variants in a given environment
=> In certain evironements certain traits are more fit or less fit than others (suitability) Such individuals are naturally selected
Natural selection (Darwin):
Explains why different genotypes have different rates of survival and reproduction in a population
= different fitness
=> We all have de novo mutations (30 or so proteins, and in an extreme example of Darwinian Natural Selection, a lethal example of de novo mutation is not viable with life and will fail in natural selection
Occasionally A/a have higher fitness than A/A & a/a => demonstrates that sometimes, possession of a partial mutated genome is beneficial
- E.g. Sickle cell anaemia (autosomal recessive)
- HbA/HbA = normal
- HbS/HbS = severe anaemia (crystallises at low O2 levels causing RBCs to become sickle-shaped and rupture)
- HbA/HbS = mild anaemia (doesn’t allow malaria entry) higher fitness in malaria areas*
Natural selection favours the retention of the HbA/HbS genotype in certain populations, despite the homozygous being fatal
Principle of heredity
Offspring resemble their parents more than
individuals to which they are unrelated*
Principle of variation
Among individual members of a population
there is variation in morphology, physiology,
and behavior*
-
-
-
-