Module 6 Bio A2

What are the three categories of gene mutation?

1. Substituion - a nucleotide base is replaced with another 2. Insertion = an extra nucleotide base is inserted into sequence causing a frameshift 3. Deletion - the absense of a nucleotide causing a frameshift

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What are the effects of mutations?

1. Neutral - may occor in an insignifcant strand of DNA/may not change structure 2. Harmful - may change final protein shape where active site is deformed 3. Beneficial - final protein shape is better than old one (natural selection & evolution)

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What is point mutation?

Where only one bases is affected, can occur in three types (silent, nonsense and missense)

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What is silent mutation?

No change in amino acid sequence of polypeptide

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What is missense mutation?

The mutation changes the code for 1 amino acid

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What is nonsense mutation?

The mutation changes the code turning the triplet into a stop codon

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Describe the lac operon in the absence of lactose

1. Regulator gene expressed & repressor protein synthesised 2. One site binds to lactose, other binds to operator region 3. Repressor binds to operator region & covers part of RNA polymerase bonding site 4. RNA pol cannot bind to promoter region

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Describe the lac operon in the presence of lactose

1. Lactose inducer binds to other side of repressor changing its shape 2. Repressor can bind to operator and break away 3. Promoter region unblocked 4. RNA polymerase able to bind to this region 5. System acts as molecular switch to translate enzymes

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What are homeobox genes?

Genes that turn off/on development of specific body parts, grouped together in a hox cluster. They regulate the development of embryos along anterior-posterior axis.

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What is apoptosis?

Programmed cell death occurring in multi-cellular organisms

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How does apoptosis take place?

1. Enzymes break down cell cytoskeleton 2. Cytoplasm becomes tightly packed with organelles 3. Cell surface membrane changes & blebs form 4. DNA breaks into fragments 5. Cells breaks into vesicles, which are taken up by phagocytosis

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What chemical induces apoptosis?

Nitric Oxide

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What affect does apoptosis have on development?

Causes limbs and appendages to separate & weeds out ineffective T-lymphocytes during development of immune system

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What are transcription factors?

Proteins or non-coding pieces of RNA that attach/detach from DNA to control which genes are expressed

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What are introns & exons?

Introns - regions of DNA that don't code for genes Exons - regions of DNA that are expressed

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Define genotype

Genetic makeup of an individual

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Define phenotype

Visual characteristics of an individual

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What are the 2 ways mutations can be caused?

1. Mutations caused by x-rays, tobacco smoke chemicals, viruses, gamma rays 2. Deletion, insertion, translocation, duplication, non-disjunction

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What is aneuploidy?

Chromosome number is not a multiple of the haploid number for that organism

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What is polyploidy?

Diploid gamete fertilised by a haploid gamete

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What is a monohybrid?

Single Characteristic

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What is a dihybrid?

Two Characteristics

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What is linkage?

When two or more genes are located on the same chromosome

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What is autosomal linkage?

Linked genes which are on non-sex chromosomes

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What is sex linkage?

Linked genes are on sex chromosomes - therefore specific characteristic is more likely to be inherited in either male or female

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What is epistasis?

Interaction of non-linked genes where on masks the expression of the other

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What is co-dominance?

When both alleles present in the genotype contribute to the phenotype

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What is the Chi-squared test?

Statistical test to find out whether the difference between observed vs expected data is due to chance

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When would the Chi-squared test be used?

1. The data are in categories 2. The sample size is large enough to be representative 3. Dealing with absolute numbers (not percentages) 4. No data values equal to null

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What is discontinuous variation?

When phenotypes are in distinct categories (blood type, sex) - determined by a single allele (monogenic) & qualitative

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What is continuous variation?

When phenotypes fall into a range (weight, height) - controlled by more than one gene (polygenic), quantitative

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What is directional selection & what does the graph look like?

Environment favours individuals at one extreme of the bell curve where the mean changes

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What is stabilising selection & what does the graph look like?

Environment favours individuals close to a specific value which doesn’t change, individuals with extreme phenotypes are less likely to survive

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Define genetic drift

Occurs when population is small to begin with (small gene pool), chance mutations that are not beneficial or harmful might cause changes in allele frequency leaving isolated population to drift and become different to parent population

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Define genetic bottleneck

When a population shrinks and then increases again, the new population has reduced genetic diversity and their genes derive from the individuals

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Define founder effect

If a new population is established from very few ‘founding’ individuals, there will be little genetic diversity (small gene pool) - this is a specific type of genetic drift

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What does Hardy Weinberg Principle predict?

The ongoing frequencies of alleles and genotypes within a closed, freely and randomly breeding population.

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What does Hardy Weinberg Principle assume?

1. Large Population 2. No immigration or migration 3. No mutation to new alleles 4. Random mating

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What is speciation and how does it occur?

The formation of a new species 1. Parent species split into 2 groups 2. Isolation occurs between groups 3. There are different selection pressures on each group 4. Speciation occurs when individuals can no longer interbreed

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What are the two isolating mechanisms?

1. Geographical Isolation (by mountains/rivers/rock slides) 2. Reproductive Isolation (Biological/behavioural changes arise from mutation, mutation only affects individuals in population like only being awake at night)

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What is hybrid vigour?

Caused by artificial selection due to excessive selective cross-breeding causing inbreeding depression (can be avoided by breeders maintaining a resource of genetic material)

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What are the ethical implications of artifical selection?

1. Domesticated animals are less able to defend themselves against predators 2. Livestock animals may not lead a happy life 3. Pedigree dogs subject to narrow gene pool and have a higher susceptibility to diseases

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What is PCR?

Polymerase Chain Reaction used to amplify DNA

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What is the process of PCR?

1. Heat to 95°C to break hydrogen bonds 2. Cool to 55°C to add primers to end of strands 3. Add DNA Polyermase and heat to 72°C to allow nucleotides to bond 4. Forms double of the DNA that you started with

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What are the uses & problems of PCR?

Uses: Cloning, Electrophoresis, Gene Probes Problems: Any contamination will be amplified

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What is a primer?

Short single stranded DNA

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What is DNA polymerase described as?

Thermophillic as it requires a temperature to work - optimum is 72°C

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What is the sequence of automated DNA sequencing?

1. Primer anneals at the 3' end, allowing DNA polymerase to attach 2. DNA polymerase adds free nucleotides, so strand grows 3. A modified nucleotide is added 4. Enzyme is thrown off 5. Reaction stops 6. Every final nucleotide strand has a colour

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How are these sequences analysed afterwards?

They are put into a machine and ordered from shortest to longest nucleotide sequence, the colours are then read in order and the sequence is found.

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What is the sequence of pyrosequencing?

1. DNA cut into fragments 2. Fragments degraded into single strand DNA 3. Fragments incubated with primer and DNA polymerase 4. Nucleotides added form chains complementary to DNA fragments 5. Visible light used to indicate DNA sequence

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What are the applications of DNA sequencing?

1. Comparison between species 2. Comparisons between individuals 3. Predicting amino acid sequences 4. Synthetic biology (biomedicine/food production)

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What is Electrophoresis?

Uses electric currents through agarose gel to separate DNA fragments according to size

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How does electrophoresis occur?

1. DNA samples treated with REs to cut them into fragments 2. DNA samples places into wells of gel 3. Gel immersed in a tank of buffer solution 4. Phosphate groups make DNA negatively charged so diffuses through gel towards cathode

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What is the process of DNA Profiling?

1. DNA obtained from individual (e.g. mouth swab) 2. Cut by REs at specific sites 3. Fragments separated by gel electrophoresis 4. Banding pattern compared to another individuals (treated with same RE) 5. Related individuals have similar band pattern

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When is DNA Profiling used?

1. Establishing innocent suspects 2. Identifying war criminals 3. Identifying victim's body parts 4. Used to analyse disease

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How does genetic engineering take place?

1. Specific gene is isolated and copied 2. Gene is placed inside a vector 3. Vector carries gene to target cell 4. Recipient cell now has recombinant DNA and expresses newly acquired gene

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How is a gene isolated?

1. mRNA coding for gene obtained 2. Reverse transcriptase forms single strand complementary DNA 3. Adding primers & DNA polymerase catalyses formation double stranded DNA 4. Gene is synthesised 5. DNA probe locates gene 6. Gene isolated by REs

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How is a gene placed inside a vector?

1. Plasmid is cut at specific site using REs that match ends of isolated gene 2. DNA ligase catalyses insertion of gene into plasmid (gene can also be sealed in an attenuated virus)

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How does a vector carry the gene to a target cell?

Many methods: 1. Heat Shock (fluctuate temp between 0-42°C making walls more permeable) 2. Electroporation (high voltage = permeable) 3. Electrofusion (electrical fields cause DNA to enter cells) 4. Transfection (bacteria cell is infected)

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What are the benefits of genetically modified organisms?

1. GM viruses which have no effect to make vaccines 2. Gene therapy 3. GM mice for medical research 4. GM rice contains beta carotene to reduce blindness 5. GM plantain better for you 6. GM E. coli makes human insulin to treat diabetics

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What are the hazards of genetically modified organisms?

1. Modification can increase cancer risk (gene therapy) 2. Welfare concerns 3. Artificial DNA can harm own genomic sequence 4. Must be carefully contained or genes could spread and will affect entire ecosystem

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What is somatic gene therapy?

An engineered gene for a functional allele inserted into a somatic cell will only be present in those cells, it cannot be passed onto offspring. It can be used to treat recessive genetic disorders (cystic fibrosis).

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What is germ line gene therapy?

Engineering a gene into a stem cell from an early embryo would result in all cells in the organism containing the engineering gene

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What are the advantages of natural cloning?

1. Same environment suitable for parent and offspring 2. Rapid 3. Reproduction doesn't require two parents or sexual reproduction

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What are the disadvantages of natural cloning?

1. Offspring overcrowding 2. No genetic diversity/variation therefore selection is impossible 3. Entire population vulnerable to environmental changes

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What is the difference between reproductive cloning & non-reproductive cloning?

Reproductive cloning makes another organism, whereas non-reproductive cloning is to produce embryonic stem cells

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Describe the process of reproductive cloning by splitting of embryos

1. Zygote is created in IVF 2. Allowed to divide by mitosis to form as small ball of cells 3. Cells are separated and allowed to continue dividing 4. Each small mass of cells is placed into the uterus of a surrogate mother

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Describe the process of reproductive cloning by somatic cell nuclear transfer

1. Egg is obtained and nucleus removed 2. Somatic cell from adult is isolated 3. Egg cell and somatic cell fused by applying electric shock 4. The shock triggers egg cell to start developing 5. Cell undergoes mitosis 6. Embryo placed into uterus

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How are plants cloned?

1. Cells taken from shoot tip with sterile forceps 2. Placed in nutrient agar 3. Cells form big ball of cells (callus) 4. Cells treated with shoot stimulating hormones 5.Cells grow into plantlets treated with root-stimulating hormones 6. Plants grow

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What are the advantages and disadvantages of cloning in plants?

Advantages: 1. Farmers know what crop will be like 2. Reduced costs as harvested at same time 3. Crop has ideal features Disadvantages: 1. One disease can affect the whole population

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What is non-reproductive cloning used for?

1. Replacement of damaged tissues 2. Future use (growing organs for transplant to avoid rejection) 3. Scientific research (drug testing)

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What are the advantages of using microorganisms in biotechnology?

1. Cheap and easy to grow 2. Reproduce quickly 3. Production at low temp & atmospheric pressure 4. Not climate dependent 5. Can be fed on waste 6. Easy to gm 7. Few ethical considerations 8. Product more pure than chemical engineering

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What are the conditions to be controlled when fermenting microorganisms?

1. Temperature 2. Nutrient Availability 3. Oxygen Availability 4. pH 5. Concentration of product

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How is the fermenter sterilised before use?

With superheated steam

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What would contamination cause during fermentation?

1. Reduce synthesis of desired product 2. Unwanted microorganisms would compete for nutrients reducing the yield of product 3. Other microorganisms could produce toxic chemicals or destroy cultured organisms

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How is penicillin manufactured?

1. Penicillin secretes by fungus 2. Fermenter runs for 6-8 days 3. Fungus mycelium removed 4. Organic solvent added to dissolve penicillin 5. Potassium salt added to make precipitate 6. Mixed with inert substance and prepared for administration

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What is a continuous culture?

Products made during normal metabolism & are released continuously, broth gets toped with nutrients - production of insulin

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What is a batch culture?

Product made by microorganisms under stress (high population or limited nutrient) - production of penicillin

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Describe the standard growth curve for a culture of microorganisms

1. Lag phase - organisms are adjusting to surrounding conditions 2. Log (exponential) phase - Population doubles in size 3. Stationary phase - nutrient levels decrease, carrying capacity 4. Decline due to nutrient exhaustion & toxic waste products

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What are the advantages of using microorganisms to make food?

1.. Protein produced faster than animals 2. Made according to demand 3. No fat/cholestrol 4. Required small land surface area 5. Independent of seasons

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What are the disadvantages of using microorganisms to make food?

1. Unappetising 2. Protein needs to be purified 3. Amino acid profile different from animal protein 4. Different texture and taste to meat 5. Cultures could be contaminated with pathogenic organisms

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What is an immobilised enzyme?

An enzyme that is fixed and unable to move freely throughout a solution

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What are the advantages of immobilising enzymes in biotechnology?

Enzymes don't mix with product, enzymes can be re-used (cheaper), enzymes are fixed within immobilising matrix which protects them from harsh environments (high temp/extreme pH more feasible)

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What are the disadvantages of immobilising enzymes in biotechnology?

Expensive to set up & immobilised enzymes are less active than free enzymes so process is slower

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What are the methods immobilising enzymes?

1. Adsorption 2. Covalent bonding 3. Entrapment 4. Membrane barrier

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Module 6 Bio A2

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