Mutations, Genetic Drift, & Gene Flow

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Genetic Drift, Mutations, & Gene Flow

Random events like mutations, genetic drift, and gene flow drive evolution and can change the genetics of a population.

Genetic drift & mutations

By chance, some alleles are passed onto offspring and some are not.
This causes random changes in the allele frequencies in the population.
- This affects the evolution of a population and is called genetic drift.
As mentioned previously, mutations are random changes in the sequence of DNA.
- Mutations are a source of new alleles, or new genetic variation, in any population.

Small populations

Genetic drift tends to have a larger influence on evolutionary change in smaller populations.
This is because the gene pool (the sum of all the genes of a population) is smaller.
If the gene pool is smaller, any change in allele frequencies has a larger impact on the overall gene pool.

Genetic bottlenecks

A population can go through a genetic bottleneck.
A genetic bottleneck is a sudden reduction in genetic variation in a population.
Bottlenecks can be caused by environmental factors like disease, flooding, drought, and famine.
A smaller gene pool means that genetic drift has more of an impact on these populations.

Founder effects

When a new population is founded, their genetic variation is only a subset of the original population.
Often, a population is founded by a small number of individuals, and their genetic variation is unlikely to be representative of the population that they came from.
Small numbers increase the impact of genetic drift in these populations.

Founder effect - example

The founder effect is believed to have been a key factor in the genetic history of the Afrikaner population of Dutch settlers in South Africa.
This is evidenced by mutations that are common in Afrikaners but rare in most other populations.
This is likely due to the fact that a higher-than-normal proportion of the founding colonists carried these mutations.
As a result, the population expresses unusually high incidences of Huntington’s disease (HD) and Fanconi anemia (FA).

Gene flow

Gene flow is the flow of alleles in and out of a population due to the migration of individuals or gametes.
While some populations are fairly stable, others experience more flux.
- Many plants, for example, send their pollen far by wind to pollinate other populations of the same species some distance away.
This variable flow of individuals changes the gene structure of the population and can also introduce new genetic variation to populations in different locations.

1Cell Biology

2Molecular Biology

2.1Water

2.1.1Water & Hydrogen Bonding

2.1.2IB Multiple Choice - Water & Hydrogen Bonding

2.1.3Extended Response - Water

2.2Carbohydrates & Lipids

2.2.1Monosaccharides

2.2.2Disaccharides & Polysaccharides

2.2.3Triglycerides & Phospholipids

2.2.4Cellulose

2.2.5Starch & Glycogen

2.3Proteins

2.3.1Structure & Functions of Proteins

2.4Enzymes

2.4.1Enzymes

2.4.2Factors Affecting Enzyme Activity

2.4.3Enzyme-Controlled Reactions

2.4.4End of Topic Test - Enzymes

2.5Structure of DNA & RNA

2.5.1DNA & RNA

2.6DNA Replication, Transcription & Translation

2.6.1Protein Synthesis

2.6.2Transcription & Translation

2.6.3End of Topic Test - DNA, Genes & Protein Synthesis

2.6.4Exam-Style Question - Protein Synthesis

2.6.5End of Topic Test - Coronavirus Translation

2.6.6IB Multiple Choice - Transcription

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2.7Cell Respiration

2.7.1Overview of Respiration

2.7.2Anaerobic Respiration

2.7.3End of Topic Test - Anaerobic Respiration

2.7.4Respiration Experiments

2.7.5End of Topic Test - Respiration

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2.8Photosynthesis

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3Genetics

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4.1Species, Communities & Ecosytems

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4.1.2Communities & Measuring Diversity

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4.1.4Overview of Ecosystems

4.1.5Nutrient Cycles

4.1.6Fertilisers

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4.2Energy Flow

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5Evolution & Biodiversity

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6Human Physiology

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6.3Defence Against Infectious Disease

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6.3.5Vaccines

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6.4Gas Exchange

6.4.1Lung Structure & Alveoli

6.4.2Ventilation

6.4.3Lung Disease

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6.5Neurons & Synapses

6.5.1Neuron Structure

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6.5.3Speed of Transmission

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6.5.5Synapses

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6.6Hormones, HomeoStasis & Reproduction

6.6.1Overview of Homeostasis

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6.6.5Type I & Type II Diabetes

6.6.6Human Reproductive Systems

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7AHL: Nucleic Acids

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7.2Transcription & Gene Expression

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7.2.2Types of RNA

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7.2.4RNA Processing in Eukaryotes

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7.3Translation

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8AHL: Metabolism, Cell Respiration & Photosynthesis

8.1Metabolism

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8.2Cell Respiration

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8.3Photosynthesis

8.3.1Light-Dependent Reaction

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9AHL: Plant Biology

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9.3Growth in Plants

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10AHL: Genetics & Evolution

10.1Meiosis

10.1.1Stages of Meiosis

10.2Inheritance

10.2.1Linked Genes

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10.2.3Non-Nuclear Inheritance

10.2.4Chi-Squared Test

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10.2.6IB Multiple Choice - Non-Mendelian Genetics

10.2.7Introduction to Non-Mendelian Inheritance

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10.2.9Grade 4-5 (Scientific Practices) - Inheritance

10.3Gene Pools & Speciation

10.3.1Populations

10.3.2Mutations, Genetic Drift, & Gene Flow

10.3.3Speciation

10.3.4Rate of Speciation

10.3.5Allopatric & Sympatric Speciation

11AHL: Animal Physiology

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11.1.5Vaccines

11.2Movement

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11.3The Kidney & Osmoregulation

11.3.1Kidneys & Osmoregulation

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