Exploring Genetic Population: Understanding the Diversity and Evolution of Life, Summaries of Genetics

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Population genetics

Kiarash Alidousti

Population genetics

• (^) Population genetics is the study of

genetic variation within and

among populations and the

evolutionary factors that explain

this variation.

• (^) Its foundation is the Hardy - Weinberg

law , which is maintained

(surdurulebilir) as long as population

size is large, mating is at random, and

there is no mutation, selection or

migration.

Factors that affect population

genetics

▪ Population geneticists usually define

'evolution' as any change in a population's

genetic composition over time.

▪ Five factors can affect the gene pool?:

• (^) Mutation
• (^) Genetic recombination
• (^) Gene flow or gene migration
• (^) Natural selection
• (^) Genetic drift

Gene pool

▪ the combination of all the genes (including

alleles) present in a reproducing population or

species.

▪ The set of all alleles at all loci(the position of a gene on a

chromosome) is the full gene pool for the species.

▪ The gene pool increases when a mutation

changes a gene and the mutation survives. The

gene pool decreases when an allele dies out.

▪ Mutations, genetic recombination, gene flow or

gene migration, genetic drift, natural

selection are the mechanisms that cause

Random genetic drift

▪ (^) allele frequencies of a population

change over generations due to chance.

▪ (^) occurs in all populations , but its effects

are strongest in small populations.

▪ (^) may result in the loss of some alleles

(including beneficial ones) or rise to

100 percent frequency, comparing to

other alleles.

Genetic drift can have major effects when a

population is sharply reduced in size by a

natural disaster (bottleneck effect) or when

a small group splits off from the main

population to found a colony (founder

effect).

natural selection

▪ (^) The process which better adapted organisms in their

environment tend to survive and produce more offspring.

▪ (^) If a trait is advantageous and helps the individual survive

and reproduce, the genetic variation is more likely to be

passed to the next generation.

Genetic polymorphisms

▪ (^) The presence of two or more variant forms of a

specific DNA sequence that can occur among

different individuals or populations.

▪ (^) Various types of polymorphisms include:

⦁ single nucleotide polymorphisms (SNPs)

⦁ small-scale insertions/deletions

⦁ polymorphic repetitive elements

⦁ microsatellite variation

Blood Groups. All the types of

blood groups are examples of

genetic polymorphism, such as

the ABO blood group system.

Calculating Genetic Biodiversity

▪ Genetic diversity is the biological variation that

occurs within species.

▪ (^) The greater the proportion, the greater the

genetic biodiversity within a species.

▪ (^) Most genes are monomorphic, ensuring the

basic structure of a species remains constant.

▪ (^) Key Terms:

• (^) Polymorphic Gene: a gene with multiple

variations.

• (^) Monomorphic Gene: a gene with only no

different variations.

• (^) Loci: the position of a gene on a chromosom.

⦁ The proportion of

polymorphic genes can be

calculated using the

following formula

Proportion of polymorphic

gene loci = Total number of

Polymorphic Gene Loci ÷

Total number of all gene

loci (x100%).

Inbreeding and population structure

▪ (^) The mating of individuals or organisms that are closely

related through common ancestry.

▪ (^) opposed to outbreeding, which is the mating of

unrelated organisms.

▪ (^) increases the frequency of homozygous genotypes and

decreases the frequency of heterozygous genotypes in

the population.

▪ (^) Risk of having recessive disorders increases.

▪ (^) The degree of inbreeding can be measured using a

calculation called the coefficient of inbreeding (CoI), or

inbreeding coefficient.

Resources

• (^) Population Genetics, 2nd Edition ( Matthew B.

Hamilton).

• (^) https://www.britannica.com/
• (^) Genetic variation in natural populations: Patterns and

theory (EviatarNevo)