GENETICS, EVOLUTION

AND ECOSYSTEMS

BIOLOGY NOTES

MODULE 6

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INDEXTOPIC 1: CELLULAR CONTROL . . . . . . . . . . . . . . . . . . . . . . 6

1. Types of Gene Mutations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Gene Expression Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. The Genetic Control of Embryonic Development . . . . . . . . . . . . . . . . . . . . . . . . 9

TOPIC 2: PATTERNS OF INHERITANCE . . . . . . . . . . . . . . . . 12 1. Phenotypic Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2. Genetic Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3. Linkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4. Epistasis and Codominance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. TheChi-Squared(χ2)Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Continuous and Discontinuous Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7. Factors Affecting Species Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8. The Hardy–Weinberg Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9. Isolating Mechanisms in the Evolution of New Species . . . . . . . . . . . . . . . . . . . . 20 10. Artificial Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 11. The Ethics of Artificial Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

TOPIC 3: MANIPULATING GENOMES . . . . . . . . . . . . . . . . . 23 1. DNA Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2. Applications of DNA Sequencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3. DNA Profiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4. ThePolymeraseChainReaction(PCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 5. Electrophoresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 6. Genetic Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 7. The ethics of Genetic Manipulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8. Gene Therapy in Medicine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

TOPIC 4: CLONING AND BIOTECHNOLOGY . . . . . . . . . . . . . 32 1. Natural Clones in Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 2. Natural Clones in Animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3. Artificial Clones in Animals Produced

by Artificial Embryo Twinning or by Enucleation & SCNT . . . . . . . . . . . . . . . . . . 34 4. Microorganisms in Biotechnological Processes . . . . . . . . . . . . . . . . . . . . . . . . 34 5. The advantages/disadvantages

of using Microorganisms to Make Food for Human Consumption . . . . . . . . . . . . . 35 6. Aseptic Culture Technique for Microorganisms . . . . . . . . . . . . . . . . . . . . . . . . 36

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7. Manipulating the Growing Conditions in Fermentation . . . . . . . . . . . . . . . . . . . 37 8. The Growth Curve of a Microorganism in a Closed Culture . . . . . . . . . . . . . . . . . 38 9. Immobilised Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

TOPIC 5: ECOSYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . 43 1. Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 2. Biomass Transfer Through Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 3. Recycling Within Ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4. Primary succession . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5. Measuring the Distribution and Abundance of Organisms in an Ecosystem . . . . . . . 48

TOPIC 6: POPULATIONS AND SUSTAINABILITY . . . . . . . . . . . 50 1. The Factors that Determine the Size of a Population . . . . . . . . . . . . . . . . . . . . . 50 2. Conservation and Preservation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3. Ecosystem Management for Sustainability . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4. The Management of Environmental Resources and the Effects of Human Activities . . . 53

TOPIC 1

Cellular Control

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Cellular Control1 Types of Gene Mutations

Gene mutations are natural occurrences that come about during DNA replication. There are 3 categories of gene mutations:

Substitution = a nucleotide base is replaced with another

Insertion = an extra nucleotide base is inserted into the sequence causing ‘frameshift’ where all the subsequent bases are shifted down 1 place relative to the twin DNA strand

Deletion = the absence of a nucleotide, causing ‘frameshift’ where all the subsequent bases are shifted back 1 place relative to the twin DNA strand

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The effects of these mutations can be..

• Neutral ○ May occur in phenotypically insignificant strand of DNA ○ Maynotresultinchangeofpolypeptideprimarysequence(becauseDNAisdegenerate) ○ May result in a change of polypeptide primary sequence that does not affect secondary/tertiary/quaternary structure of protein therefore protein function unaffected

○ May results in a change of polypeptide secondary/tertiary/quaternary structure but where active site of protein remains the same therefore function still unaffected

• Harmful ○ May result in change in final protein shape where protein and active site is deformed and therefore cannot fulfil function

• Beneficial ○ May result in change in final protein shape where the protein performs its function better than it would have without the mutation

○ This is the basis of natural selection and evolution ○ The individual is better suited to survival and will pass on the mutation to its offspring ○ E.g. eye colour

– Blue eyes was a mutation that occurred about 7000 years ago – In sunny areas, this would be harmful as the retina is more exposed – However in cloudy regions this was beneficial as it enabled people to see better – So the mutation was carried down generations and became widespread

Point mutation

• Mutations can affect 1 nucleotide base, or more than one adjacent bases • A point mutation is where only one base is affected • There are 3 types: silent, nonsense, missense • Silent mutation

○ No change in amino acid sequence of polypeptide • Missense mutation

○ The mutation changes the code for 1 amino acid ○ 1 amino acid in the sequence is changes

• Nonsense mutation ○ The mutation changes the code turning the triplet into a stop codon ○ Instructs the end of polypeptide synthesis ○ The polypeptide is shorter than it would normally be

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