Chapter 9,10,11 SAC: Flashcards
Mutation:
a permanent change to a DNA sequence
- For a mutation to be heritable, it must occur in a germline(sex) cell as this means it can be passed on to future generations
Mutagens:
an agent that causes mutations in DNA
Point Mutations:
a mutation that alters a single nucleotide in a DNA sequence
Silent Point Mutation
a mutation in which a nucleotide is substituted for another nucleotide which results in a different codon that still codes for the same amino acid and therefore does not affect protein structure
Missense Point Mutation
a mutation in which a nucleotide is substituted for another nucleotide resulting in a different codon which codes for a different amino acid and therefore affect protein structure
Nonsense Point Mutation
a mutation in which a nucleotide is substituted for another nucleotide resulting in a stop codon, prematurely ceasing translation of the genes mRNA affecting protein structure.
Frameshift Point Mutation
a mutation that involves the insertion or deletion of one or two nucleotides in a sequence, altering every codon from that point onwards, affecting protein structure
Block Mutations:
a mutation that affects a large chunk of DNA or an entire gene
- These mutations usually occur during meiosis
Deletion Block Mutation:
the removal of a section of DNA
Duplication Block Mutation:
the replication of a section of DNA, lengthening the original strand of DNA
Inversion Block Mutation
the reversal of a section of DNA
Translocation Block Mutation:
the switching of two sections of DNA on different chromosomes
Speciation:
the process by which populations genetically diverge until they become distinct species
Allopatric Speciation:
the geographical separation of a population from a parent population resulting in the formation of a new species
- Relies on the presence of a geographical barrier
Process of Allopatric Speciation:
1.Original population has variation in its genetic frequencies
- A geographical barrier separates a population, preventing gene flow
- Different selection pressures act upon each population, favouring different phenotypes and allowing for genetic differences to accumulate
- Eventually sufficient genetic differences accumulate so that the two populations can no longer interbreed to produce viable and fertile offspring
Example of Allopatric Speciation:
- The Galapagos islands is a collection of 19 islands with 19 different ecological niches on each island(selection pressures and species) inhabited by Galapagos finches
- Islands are also separated by the ocean which serves as a geographical barrier, preventing gene flow between them
- As each different island has different food sources and selection pressures, different phenotypes(beak shape) are more advantageous, allow for genetic differences to accumulate and therefore for a new species to form
3 different species of Galapagos Finches:
Cactus Finch:
- Has a thin and elongated beak
- Primarily sources food from cacti using thin and elongated beak to prevent contact with spikes
Large-ground Finch:
- Thick and Short beak
- Primarily sources food from hard woody nuts with their thick and short beaks providing a significant amount of force to break open and extract the interior of woody nuts
Medium Ground Finches:
- Have moderate width and short beaks
- Primarily source their food from soft seeds
Sympatric Speciation:
the divergence of a new species from an original species located in the same geographical area as a result of different selection pressures acting on different phenotypes
- Does not rely on the presence of a geographical barrier
- generally occurs in plants
Example of Sympatric Speciation:
- The differences in soil pH on the Lord Howe Island is a major catalyst for the sympatric speciation between the Howea Forsteriana and Howea Belmoreana
- Howea Belmoreana inhabits neutral and acidic soils(Low pH) whereas Howea forsteriana inhabits a region of alkaline soil(high pH)
- The selection pressure of Howea Forsteriana inhabiting the alkaline soil resulted in the divergence of the sister species after the physiological differences began to develop, which after generations and generations, resulted in the formation of Howea Belmoreana
Natural Selection:
a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles
4 Conditions of Natural Selection:
- Variation: Individuals in a population vary genetically, which leads to phenotypic differences
- Selection Pressure: an environmental selection pressure impacts the survivability of organisms within a population and their ability to reproduce
- Selective Advantage: Individuals with phenotypes that are fitter or more advantageous under the environmental selection pressures are conferred a selective advantage, allowing them to survive and reproduce more successfully.
- Heritability: The advantageous trait must be heritable, allowing it to be passed on from the parents to their offspring. Therefore over time, the frequency of the advantageous allele will increase
Selective Breeding/Artificial Selection:
the changing of a populations gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait
- Can be used to select for the desirable trait but can also be used to select against an unwanted trait to remove it from a population - Difference to natural selection is that NS involves a naturally occurring environmental selection pressure(predation, disease or climate change) which select individuals with a selective advantage within their environment
Requirements for Selective Breeding:
- Variation: individuals in a population vary genetically, resulting in phenotypic differences
- Selection Pressures: direct human intervention places an artificial selection pressure upon a population of individuals only allowing certain individuals with desirable traits to breed.
- Heritability: the trait selected must be heritable, allowing it to be passed on from the parents to their offspring. Selected allele will increase in frequency
Genetic Drift:
a random event that dramatically alters a population’s gene pool
- Reduces genetic diversity in a population through the random removal of alleles from the gene pool
- Smaller populations are more susceptible
Bottleneck Effect:
a type of genetic drift which causes the reduction of genetic diversity that occurs when a large proportion of a population is removed due to a chance event
- They can dramatically reduce a population size and therefore allele frequencies
