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Genetic Diversity - Coggle Diagram
Genetic Diversity
Mutations
- A change in the amount or structure of DNA.
- Substitution - a nucleotide is substituted with another.
- Inversion - a group of bases inverted in same position in the sequence.
- Duplication - one or more bases are repeated.
- Deletion - the loss of a nucleotide base from the sequence.
- Translocation - group of bases separate and become inserted in DNA sequence of different chromosome.
- Insertion - an extra base is inserted into the sequence.
Causes of mutations
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- Chemicals (cigarettes/caffeine)
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Meiosis
Meiosis I
Metaphase I
- Chromosomes randomly line up on the equator.
- This is independent assortment and increases variation.
Anaphase I
- Spindle fibres attach to centromeres and pull chromosomes to opposite ends of the cell.
- Homologous chromosomes are separated.
Prophase I
- Replicated chromosomes condense and become visible.
- Homologous chromosomes meet up and exchange genetic material - crossing over.
Telophase I
- Two new daughter cells are created.
- The cells are haploid - they only have 1 of the homologous chromosomes.
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- But the chromosomes are still replicated - they have a sister chromatid.
Meiosis II
Metaphase II
- Chromosomes line up along the equator.
Anaphase II
- Sister chromatids are pulled apart by the centromere to opposite ends of the cell.
Telophase
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- Four genetically different haploid cells are formed.
Prophase II
- Spindle fibres form at the poles of each new cell.
Types of selection
- Selection may favour individuals that vary in one direction from the mean of the population. This is called directional selection and changes the characteristics of the population.
- Selection may favour average individuals. This is called stabilising selection and preserves the characteristics of a population.
- Natural selection results in species that are better adapted to the environment that they live in. Their adaptions may be anatomical (e.g. shorter ears), physiological (e.g. oxidising of fat), or behavioural (e.g. autumn migration).
Definitions
- Meiosis - a type of nuclear division where the number of chromosomes is halved.
- Mitosis - a type of nuclear diision where the daughter cells have the same number of chromosomes as the parent cell.
- Mutation - a sudden change in the amount or arrangement of genetic material in a cell.
- Mutagen - any agent that induces a mutation.
- Allele - one of alternative forms of a gene.