part 4 Flashcards
What conditions are necessary for the lac operon to be switched on?
Glucose absent, lactose present
How can the action of RNA polymerase in lac operon be up-regulated?
Binding of the CRP-cAMP complex to RNA polymerase
How does cAMP levels within the cell affect the rate of lactose metabolism?
Move glucose into cell decreases cAMP levels –> less transcription of lac operon –> less lactose metabolised
Give one way of transcriptional control in eukaryotic cells.
Converting heterochromatin to euchromatin
What is heterochromatin?
Tightly wound DNA around histones during cell division, visible under light microscope
What is euchromatin?
Loosely wound DNA during interphase, invisible under light microscope
At which state would the DNA be during cell division - heterochromatin or euchromatin?
Heterochromatin
At which stage of cell division would gene expression occur?
Interphase (G1 + G2)
Why can gene expression only occur with euchromatin?
Loosely wound DNA, therefore RNA polymerase can access/bind to genes
Explain how heterochromatin is converted to euchromatin.
Aceylation or phosphorylation of histones –> decrease its positive charge so negatively charged DNA is less attracted to it
Explain how euchromatin is converted to heterochromatin.
Methylation of histones –> make histones more hydrophobic to bind to each other more, wounding up the DNA more tightly
Give one way of transcriptional gene regulation.
Transcription factors
What are transcription factors?
Proteins or non-coding RNA that regulate the transcription of genes.
What 2 areas do transcription factors bind to?
Promoters, enhancers
What has happened if a transcription factor has repressed a gene?
The TF has attached to the promoter, preventing the attachment of RNA polymerase and expression of the gene.
What has happened if a transcription factor has up-regulated a gene?
The TF has attached to the enhancer, aiding the attachment of RNA polymerase to the promoter and expression of the gene.
Give one way of post-transcriptional gene regulation.
Maturing of mRNA through removal of introns.
What is an intron?
A non-coding region of DNA / RNA.
What is an exon?
A coding region of DNA / RNA.
What is pre-mRNA?
mRNA containing both introns and exons.
What is mature mRNA?
mRNA containing only exons (introns have been removed).
What is alternative splicing?
The joining of exons in a region of mRNA in different combinations resulting in one gene encoding more than one protein.
Give one way of translational gene regulation that up-regulates translation.
Activating initiation factors (through phosphorylation by kinases) to help mature mRNA to bind to ribosomes
Give one way of translational gene regulation that inhibits translation.
Degrade mRNA / Inhibition proteins bind to mRNA to prevent it from binding to ribosomes
Give one way of post-translational gene regulation.
Cyclic AMP to activate CRP or kinases / protein modification or further folding
What enzyme catalyses the formation of cyclic AMP from ATP?
Adenyl cyclase
What activates protein kinase A (PKA)?
Cyclic AMP
What is the function of protein kinase A (PKA)?
Activate enzymes / transcription factor proteins by phosphorylation.
What is a homeobox gene?
A gene controlling the anatomical development of an animal, plant or fungus.
Why are homeobox genes highly conserved in plants, animals and fungi?
Highly conserved anatomical structure ensures survival and reproduction
What is the homeobox sequence?
A sequence of 180 DNA base pairs found in all homeotic / homeobox genes –> codes for the homeodomain of regulatory proteins
What is the homeodomain sequence?
A sequence of 60 amino acids encoded by the homeobox sequence.
What is a Hox gene?
A homeobox / homeotic gene found only in animals.
What type of genes are homeotic / homeobox / Hox genes?
Regulatory
How many Hox gene clusters are found in humans?
4
What is apoptosis?
Programmed cell death
How is apoptosis different to cell death due to trauma?
Apoptosis does not involve hydrolytic enzymes.
What is a bleb in terms of apoptosis?
A protusion from a cell early on in apoptosis.
What are 4 uses of apoptosis in plant and animal tissue development?
Separation of limbs and digits in embryonic development, removal of anti-self T/B lymphocytes, immune response to viral infection, prevent tumour growth
What is a genotype?
An individual’s unique genome / collection of alleles.
What is a phenotype?
The visible characteristics of an individual as a result of their genotype interacting with the environment.
What is an allele?
A version of a gene (as a result of mutation).
What are the 3 causes of genetic variation in a population?
Mutation, meiosis, random fertilisation
What are the 3 causes of genetic variation that occur during meiosis?
Crossing over / chiasmata / allele shuffling, independent assortment in meiosis I, independent assortment in meiosis II
When does allele shuffling due to crossing over occur during meiosis?
Prophase I
When does independent assortment of chromosomes occur during meiosis?
Metaphase I
When does independent assortment of chromatids occur during meiosis?
Metaphase II
What are the 4 chromosomal mutations that can occur during meiosis?
Deletion, inversion, translocation, duplication
What are the 3 features of discontinuous genetic variation?
Qualitative differences in phenotype, no intermediate phenotypes, usually monogenic
What are the 3 features of continuous genetic variation?
Quantitative difference in phenotypes, a range of phenotypes, polygenic
Name 2 examples of environmental variation.
Dialect / accent, scar
What is a gene locus?
The position of a gene on a chromosome.
How many alleles are inherited for a single gene?
2
How many dominant alleles are needed for its phenotype to be expressed?
1
How many recessive alleles are needed for its phenotype to be expressed?
2
What is meant if an individual is homozygous at a gene locus?
Alleles are identical.
What is meant if an individual is heterozygous at a gene locus?
Alleles are different
What is meant by a true-breeding individual?
An individual homozygous for a particular trait.
What does it mean if a characteristic is monogenic?
It is controlled by one gene.
What is the expected phenotypic ratio for monogenic inheritance in offspring from heterozygous parents?
3:1
What is the expected outcome for a test cross if the F2 individual is homozygous?
100% dominant phenotype.
What is the expected outcome for a test cross if the F2 individual is heterozygous?
50% dominant, 50% recessive phenotype.
What is meant by codominance?
Both alleles contribute to the phenotype in a heterozygous individual.
What is meant if a gene has multiple alleles?
There are 3 or more possible alleles within the gene pool.
What is the human male combination for the sex chromosomes?
XY
What is the human female combination for the sex chromosomes?
XX
What is meant by the homogametic sex?
Sex chromosomes that are fully homologous and so result in only one type of gamete e.g. XX
What is meant by the heterogametic sex?
Sex chromosomes that are not fully homologous and so result in 2 types of gamete e.g. XY
What is a sex-linked characteristic?
Characteristic with a gene locus on a sex chromosome.
What is an X-linked characteristic?
Characteristic with a gene locus on the X chromosome.
How many alleles do males have for an X-linked characteristic?
1
How many alleles do females have for an X-linked characteristic?
2
Haemophilia is an example of which type of inheritance?
Sex Linkage
Calculate the probability of the offspring being a female carrier if the father was a haemophiliac male and the mother carried no alleles for haemophilia.
0.5
Fur colour in cats is partly controlled by a gene on the X chromosome. The gene has two alleles, one coding for black fur and one coding for ginger fur. The two alleles are codominant, so a heterozygous cat has patches of black and patches of ginger fur, a pattern called tortoiseshell. When a black cat was mated with a ginger male, the F1 generation consisted of black males and tortoiseshell females. What phenotypic ratio would be expected in the F2 generation?
1 black female: 1 tortoiseshell female: 1 black male: 1 ginger male
What is dihybrid inheritance?
Inheritance involving 2 genes with loci on different chromosomes.
What is the expected phenotypic ratio for dihybrid inheritance in offspring from heterozygous parents?
9:3:3:1
What are autosomes?
Chromosome (pairs) that are non-sex chromosomes
What is autosomal linkage?
Multiple gene loci located on the same non-sex chromosome and inherited together.
What is the expected phenotypic ratio for the inheritance of 2 autosomally linked genes in offspring from heterozygous parents?
3:1
What is a recombinant genotype?
A genotype only possible due to meiotic crossing over.
What is epistasis?
Where one gene masks or suppresses the expression of another gene.
What is antagonistic epistasis?
Where one gene suppresses the expression of another gene.
What is an epistatic gene?
Gene that prevents the expression of another gene.
What is a hypostatic gene?
A gene whose expression is prevented by another gene.
What is recessive epistasis?
Where the epistatic gene locus must be homozygous recessive in order to prevent the expression of the hypostatic gene.
What phenotypic ratio in offspring from heterozygous parents may suggest recessive epistasis?
9:3:4
What is dominant epistasis?
Where the epistatic gene locus must have at least 1 dominant allele in order to prevent the expression of the hypostatic gene.
What 2 phenotypic ratios in offspring from heterozygous parents may suggest dominant epistasis?
13:3, 12:3:1
Epistasis is shown in the inheritance of corn colour, with gene P that codes for a purple (P) or red (p) pigment and gene C (dominant) allows the expression of gene P. If gene P is not expressed, then the corn remains yellow. If two sweetcorn plants were crossed which were heterozygous for both genes P and C, what would the probability be of the offspring being yellow?
0.25
What is complementary gene action?
Where 2 genes contribute to a final phenotype.
What 3 phenotypic ratios in offspring from heterozygous parents may suggest complementary gene action?
9:7, 9:3:4, 9:3:3:1
What statistical test can be used to determine whether the observed phenotypic ratio is significantly different from the expected ratio?
Chi-squared
What form should the null hypothesis for a chi-squared test take?
There is no significant difference between the observed and expected data. Any difference is due to chance.
What is the Hardy-Weinberg principle?
In a stable population with no disturbing factors, the allel frequencies will remain constant from one generation to the next, and there will be no evolution
What are the 2 Hardy-Weinberg equations?
p + q = 1, p2 + 2pq + q2 = 1
What are the 5 assumptions made if the Hardy-Weinberg principle applies to a population?
No mutation, random mating, no migration, large population size, no selection (natural of genetic drift)
The deer in a captive population vary in colour. 53 deer are brown and 14 are white. The coat colour of is determined by the gene R/r, where the dominant allele R codes for brown and recessive allele r codes for white. Calculate the frequency of the allele R in the population using the Hardy-Weinberg principle.
0.54
What is genetic drift?
Changes in allele frequencies caused by chance events.
What are the 2 causes of genetic drift?
Genetic bottleneck, founder effect
What is a genetic bottleneck?
When a population dramatically shrinks in size and then increases again.
What is the effect of a genetic bottleneck on genetic diversity?
Decrease
What is the founder effect?
Establishment of a new, small population of a species derived from a larger, parent population.
What is the effect of the founder effect on genetic diversity?
Decrease
Selection pressure can affect homozygous individuals. The effect can be investigated using a model gene pool. Why is a large gene pool necessary?
So the effect of chance variation in gene frequencies are minimised.
What is natural selection?
Changes in allele frequencies caused by environmental selection pressures favouring the survival of some individuals over others.
What is stabilising selection?
Natural selection that favours normal phenotypes due to unchanged environmental selection pressure
What is directional selection?
Natural selection that favours one extreme phenotype due to a change in environmental selection pressure
What is disruptive selection?
Natural selection that favours both extremes of a given phenotype due to a change in environmental selection pressures
What is speciation?
Splitting of a population into 2 or more reproductively isolated populations.
What is meant by geographical isolation?
A population that is separated and reproductively isolated by geographical barriers such as rivers, lakes, mountains.
What type of speciation is a result of geographical isolation?
Allopatric
What is reproductive isolation?
A population that is separated due to biological and behavioural changes.
What type of speciation results in reproductive isolation?
Sympatric
What is sympatric speciation?
Speciation that occurs within populations in the same habitat
What can lead to sympatric speciation?
Members of two different species interbreed and form fertile offspring (more common in plants), forming a hybrid that usually is infertile/reproductively isolated
What is artificial selection?
Selective breeding of a species by humans resulting in a change in allele frequency.
What is inbreeding?
Breeding of closely related individuals
Describe a problem with inbreeding.
Reducing the gene pool and hence genetic diversity –> reduces their chance to evolve and adapt to environmental changes / Higher chance of inheriting recessive alleles that may cause genetic disorders
What is the effect of artificial selection on genetic diversity?
Decrease
What is a gene bank?
Storage of genomes within organisms so as to provide possible new alleles for future artificial selection.
What are the 2 main ethical objections to artificial selection?
Loss of a species’ natural characteristics / behaviour, inbreeding depression
What is a DNA probe?
Single stranded piece of DNA that is complementary to a gene of interest. It is attached to a marker (tag) to identify the presence of specific genes
Which part(s) of the genome are compared in DNA profiling for forensics?
Non-coding regions (introns, STRs, VNTRs, minisatellites, microsatellites)
Put these steps for creating a DNA profile in the correct order: Amplification, Visualisation, Extraction, Digestion
What is selection?
Loss of a species’ natural characteristics / behaviour, inbreeding depression
Put these steps for creating a DNA profile in the correct order: Amplification, Visualisation, Extraction, Digestion, Separation
Extraction, Amplification, Digestion, Separation, Visualisation
Give 2 uses of DNA profiles.
Paternity testing, forensic investigations, determining how closely related organisms/species are, genetic screening for disease risk
State three potential sources of DNA at a crime scene.
Hair, blood, skin cells, semen, saliva etc.
Two primers are needed in PCR. What is a primer?
Short, single-stranded DNA fragment (used to ‘tell’ the DNA polymerase the part of DNA to copy)
The first step of a PCR cycle is to heat to 95oC. What happens in this step?
Double stranded DNA is separated into two single strands (hydrogen bonds break)
What is special about Taq polymerase compared to other DNA polymerases?
Very stable at high temperatures so does not denature
The second stage of PCR (after heating to 95oC) is to cool to around 55oC. What is the purpose of this step?
Allow primers to anneal (bind)
A PCR mixture must contain DNA polymerase, free nucleotides, buffer, primers and what?
The target DNA sequence to be amplified
If the number of DNA fragments doubles in each PCR cycle, how many fragments will there be if one piece of DNA goes through 15 cycles of PCR?
32768
What does PCR stand for?
Polymerase chain reaction
In gel electrophoresis, is DNA attracted to the anode (+ve) or cathode (-ve)?
Anode (DNA is negatively charged)
Describe the movement of small fragments compared to larger fragments in gel electrophoresis.
Smaller fragments move further/faster
In gel electrophoresis, what are DNA markers?
Mixtures of DNA molecules of known size. They are run in one lane and are used to estimate the sizes of the other DNA samples
In gel electrophoresis, what is the gel made of?
Agarose
What is the purpose of gel electrophoresis?
Separate DNA fragments in order of size
What is a genome?
Genes or genetic material present in a cell or organism
Give two reasons why new DNA sequencing techniques have improved upon old methods.
Quicker, cheaper
In order to use the Sanger sequencing method, apart from the DNA sample to be sequenced, what are the four other chemicals needed?
Taq DNA polymerase, a primer, normal nucleotides, chain terminator nucleotides (ddNTPs)
How is a terminator base different from a normal nucleotide?
Has a hydrogen instead of hydroxyl group on C3 of the deoxyribose sugar
How are the terminator bases altered in order for the sequence of nucleotide to be seen or detected?
Has a coloured fluorescent tag - 4 different colours for different bases
Why would the addition of the terminator base stop further extension of the DNA strand in DNA sequencing?
Terminator bases do not have hydroxyl group on C3 of deoxyribose, therefore cannot form phosphodiester bonds with the next nucleotide
What is the first step in sequencing a whole genome?
Cut the genome into smaller fragments (and clone into BACs to make a clone library)
How are the DNA fragments separated and read in DNA sequencing?
Gel electrophoresis in minute capillary tubes –> separate DNA fragments by size –> They can be read when passing through a laser that reads the colour as they pass through
Briefly describe how next-generation sequencing works.
Automated, high-throughput sequencing process: millions of DNA fragments are attached onto a surface and sequenced as clusters at the same time
Explain how genome sequencing can help identify evolutionary relationships.
Closer % match of genome sequence means less time since the two species diverged from a common ancestor.
Bioinformatics is transforming epidemiology. What is epidemiology?
The incidence, distribution, and possible control of diseases (and other factors relating to health)
What’s the difference between Bioinformatics and Computational Biology?
Bioinformatics – development of software to process large amount of data produced from sequencing etc. Computational Biology – using that data to create computer models and test theories
Name one benefit to sequencing pathogens’ genomes.
Find out the source of an infection / Identify antibiotic-resistant bacteria strains to evaluate the use of antibiotics / monitor a disease outbreak / find useful targets in genome when developing new drugs
What is proteomics?
Study and amino acid sequencing of an organism’s entire protein complement
The amino acid sequence is not always what would be predicted from the genome sequence itself. Suggest two reasons why.
1.) Genomes have exons and introns –> introns are removed + spliceosomes join different exons together in different ways to make different proteins; 2.) Protein modification by Golgi apparatus
What is DNA barcoding?
Identifying particular DNA sections that are common to all species but vary between them –> useful as comparison for evidence for evolution
Once scientists have sequenced a gene they can work out the amino acid sequence of the protein it codes for. How?
Triplet code has been worked out (i.e. all 64 combinations of three bases are known and decoded)
What is synthetic biology?
Creating biological molecules from scratch (e.g. ‘printing’ a sequence of DNA)
What is recombinant DNA?
DNA molecule artificially generated from different origins (often different species)
What is a restriction endonuclease?
Enzyme that cuts a double stranded DNA fragment at a specific place (its restriction site)
What is meant when a restriction enzyme recognition site is said to be ‘palindromic’?
It has the same sequence on both strands (reading from 5’ to 3’)
What are ‘sticky ends’ in genetic engineering?
Complementary single stranded ‘overhangs’ of DNA which can be used to stick two DNA fragments together.
Do restriction enzymes catalyse condensation or hydrolysis reactions?
Hydrolysis
What is another method of getting the desired gene apart from using restriction endonucleases?
Use reverse transcriptases
What is a reverse transcriptase?
Enzyme that makes a complementary DNA (cDNA) from the isolated mRNA made from the desired gene
What does it mean when we say that two DNA fragments are ‘annealed’?
Joined together (compatible sticky ends)
What process could you describe as the reverse of restriction digestion?
DNA Ligation
Name a common vector used in genetic engineering.
Plasmids (also cosmids, viruses, artificial chromosomes such as BACS, liposomes)
What is the role of DNA Ligase?
Joins DNA backbone/sugar phosphate backbone (makes phosphodiester bonds) of two DNA fragments together
How are restriction enzymes used in genetic modification?
Cut plasmid, isolate gene, producing sticky ends
What is electroporation?
Using an electrical current to make cell membranes more porous (to allow plasmids to enter)
What is electofusion?
Pass tiny electric currents to the membranes of two different cells to fuse them together, forming a hybrid/polyploid cell
What is a transgenic organism?
One that has been genetically altered to include genetic material from another organism
Suggest a reason for genetically modifying a plant.
Insect resistance, drought tolerance, pesticide resistance, faster growth, better flavour, slower ripening etc.
State a negative aspect of genetically modifying plants.
Create monocultures (susceptible to extinction), chance of gene transfer to create superweeds, expensive to buy
What is ‘pharming’?
Making medicinal drugs (pharmaceuticals) from genetically modified organisms
Give an ethical positive and negative to ‘pharming’.
Positive– easier/cheaper production of medicine. Negative – long term effects to health of organism unknown, patenting issues.
Give a positive and negative ethical issue of genetically engineering pathogens.
Positive - may be able to engineer them to attack cancer cells. Negative - Risk of mutation/reversion and therefore cause major outbreak of disease, intentional biowarfare
What is gene therapy?
Altering alleles to treat genetic diseases
What’s the difference between somatic cell therapy and germ line cell therapy?
Somatic - altering genes in body cells. Germ Line – altering genes in gametes or zygote
State a negative feature of somatic cell gene therapy.
Effects are often short-lived, multiple treatments may be needed, hard to target some body cells, allele could go to wrong place and cause a problem, expensive, where do we draw the line? (e.g. should we ‘fix’ shortsightedness, baldness, hair colour etc.)
State a negative feature of germline gene therapy.
Offspring will also carry altered genes - may be unknown long term effects.
Why is it harder to treat genetic disorders caused by dominant alleles than disorders caused by recessive alleles?
Recessive allele treatment just needs addition of the ‘correct’ allele anywhere in genome. Treatment of a dominant condition requires that specific gene to be disrupted/silenced. This requires more specific placement of inserted DNA.
State whether each type of gene therapy (somatic and germline) is legal or illegal.
Somatic = legal. Germline = illegal.
State 3 ways in which plants clone themselves.
Sending out runners, making suckers, producing bulbs, producing corms, producing immature plants on the leaves (e.g. kalanchoe), producing tubers
Define micropropagation.
Growing large numbers of plants from meristem tissue taken from a sample plant
Define tissue culture.
Growing new tissues, organs or plants from certain tissues cut from sample plants
In what circumstances would micropropagation be used?
If the plant doesn’t produce many seeds, doesn’t respond well to natural cloning, is rare, needs to be pathogen free, is GM or selectively bred
Outline the steps involved in micropropagation.
Cells removed from the shoot > cells /explants are sterilized before being placed onto the sterile nutrient medium > explants divide to form a callus, small clumps of undifferentiated cells > callus transferred to a new agar medium > plantlets transferred to compost
State 3 advantages of cloning plants.
Can produce lots of plants quickly, if aseptic technique is followed the new plants will be disease free, plants can be chosen with desirable traits (high-yielding, pest-resistant, disease-resistant, frost-resistant), infertile plants can be grown, harvesting is easier as all plants have the same genotype
State 3 disadvantages of cloning plants.
Expensive, can fail due to microbial contamination, all cloned offspring are susceptible to the same pest or disease (monoculture), reduces genetic variation in a species.
Describe the difference between micropropagation and tissue culture.
Micropropagation produces a large number of plants from a small sample of plant material whereas tissue culture is growing plant cells in an artificial medium, forming large numbers of plantlets (i.e. the first step in micropropagation).
Describe how to take cuttings.
Cut a 10cm section from a non-flowering stem of the plant > remove the top leaves > dip the cut end into a rooting powder > push the plant into the compost > add water to the compost and cover the plant with a plastic bag
What are explants?
Small pieces of plants cuttings taken
How are explants processed before cultured for cloning, and why?
Sterilised using bleach/ethanol/sodium dichloroisocyanurate –> avoid growth of pathogens or microorganisms that may compete with explants for resources during growth (aseptic reasons)
What chemicals need to be added to the nutrient agar plates to induce plant development during micropropagation? Give two examples.
Plant hormones: Auxins for shoot growth, cytokinins for root growth
State the term given to a ball of unspecialised plant cells produced during micropropagation.
Callus
What do we call natural human clones?
Twins.
Outline how twins / natural animal clones are formed.
One sperm fertilises one egg > mitosis produces a ball of cells called an early embryo > the embryo splits and implants in the uterus lining where mitosis continues.
Outline how embryo twinning works.
One sperm fertilises one egg > zygote divides to form an embryo > the embryo is split into separate cells > the cells divide by mitosis to form genetically identical embryos > each embryo is planted into a surrogate > offspring are born which are genetically identical to each other.
In artificial twinning, explain why the cow needs to be treated with hormones as the first step.
So it super-ovulates to release mature eggs (for collection)
In artificial twinning, the offspring are genetically identical to whom?
To each other (all offspring are clones of each other)
Which method is a type of reproductive cloning - Artificial twinning or somatic cell nuclear transfer?
Somatic cell nuclear transfer (SCNT)
Outline how somatic cell nuclear transfer cloning works.
A somatic cell is obtained and the nucleus is removed > a donor egg is obtained and enucleated > the somatic cell nucleus is inserted into the enucleated oocyte > electrofusion of the host cell and new nucleus > the transformed egg divides in vitro > the embryo is transferred into a surrogate uterus > the clone is born.
In SCNT, which cell becomes enucleated?
Mature egg cell/ovum from a female animal
How is the enucleated egg cell fused with the somatic cell nucleus?
Electrofusion
Explain why the offspring in SCNT is not an exact clone of the nucleus donor.
Different mitochondrial DNA as mitochondria are inherited from the egg cell donor
State 3 advantages of cloning animals.
Desirable traits are selected for and guaranteed to be passed on, infertile animals can be reproduced, do not need to wait for breeding season, increase populations of endangered species
State 3 disadvantages of cloning animals.
Difficult time-consuming and expensive, all are susceptible to the same disease, undesirable characteristics also always passed on, clones tend not to live as long as natural offspring
Give one use of animal cloning.
Farming / Pharming / Restore endangered animal populations
Name the microorganism used in baking.
Yeast (often Saccharomyces sp.)
Explain why bread rises.
Yeast respires, releasing carbon dioxide which gets trapped between crosslinked gluten molecules. As the temperature rises, the carbon dioxide bubbles expand.
Name the microorganism used in brewing.
Yeast (often Saccharomyces sp.)
Name the type of respiration used by microorganisms during brewing and state the products of this.
Anaerobic respiration (fermentation), producing carbon dioxide and ethanol.
Give the balanced symbol equation for fermentation of glucose.
C6H12O6 –> 2C2H5OH + 2CO2
Name the type of organism used in making cheese.
Bacteria (e.g. Lactococci and Lactobacilli sp)
Which enzyme is used in cheese making and what is the source of this?
Chymosin (from rennet), from the stomach of a calf
Name the type of organism used in making yogurt.
Bacteria (e.g. Lactobacillus or Streptococcus)
Name the type of organism involved in producing penicillin.
Fungus (Penicillium sp.)
Which microorganism is used to make single cell protein / mycoprotein?
Fungus (Fusarium sp.)
State the reactants and conditions in the fermenter when mycoprotein is made and explain why each is needed.
Fusarium fungus - to produce the mycoprotein; glucose - respiratory substrate; ammonia - to provide a nitrogen source; sterile oxygen - to ensure aerobic respiration without contaminating the mixture; pH and temperature at an optimum - to ensure maximum growth; water cooling jacket - to remove thermal energy released in respiration; stirring padd
State the reactants and conditions in the fermenter when mycoprotein is made and explain why each is needed.
Fusarium fungus - to produce the mycoprotein; glucose - respiratory substrate; ammonia - to provide a nitrogen source; sterile oxygen - to ensure aerobic respiration without contaminating the mixture; pH and temperature at an optimum - to ensure maximum growth; water cooling jacket - to remove thermal energy released in respiration; stirring paddles - to ensure thorough mixing of reactants.
State 3 advantages of producing and consuming SCP.
Suitable for vegetarians; high protein, low fat; lots can be produced in a short space of time; does not require a lot of land as fermenters are built vertically; can be transformed into different flavours and textures.
State 3 disadvantages of producing and consuming SCP.
Risk of contamination if fermenter/ reactants are not sterile; have to extract, purify and flavour the mycoprotein; some people may not want to eat fungal protein.
Is penicillin produced in batch fermentation or continuous fermentation?
Batch
Where did insulin historically come from?
Animal pancreases (e.g. pigs)
What was the problem with using insulin from animals?
Not very effective as not the same structure to human insulin, difficult to extract in large quantities, ethical concerns about the use of animals to provide insulin, not suitable for use by people with particular beliefs.
Describe the steps involved in making synthetic insulin.
Isolate the gene for insulin using restriction endonucleases > remove a plasmid from a prokaryotic cell > cut the plasmid using the same restriction enzyme > insert the gene into the plasmid > use DNA ligase to form phosphodiester bonds between the gene and the plasmid > insert the transformed plasmid into a prokaryotic cell > provide aseptic conditions with plentiful nutrients > the prokaryote will express the gene as it divides by binary fission.
Is insulin produced in batch fermentation or continuous fermentation?
Continuous
Define bioremediation.
The use of microorganisms to clean the soil and underground water on polluted sites.
Describe how bioremediation works.
Microorganisms convert toxic substances to less harmful substances.
What is the difference between in situ and ex situ bioremediation?
Contaminants are broken down on-site during in situ and taken elsewhere during ex situ.
Why is a source of carbon needed when growing microorganisms?
To provide a respiratory substrate.
Why is a source of nitrogen needed when growing microorganisms?
To allow protein synthesis to occur.
What is the jelly-like substance called on which microorganisms are often grown?
Agar
What is meant by a closed culture?
A culture which has no exchange of nutrients or gases with the external environment.
Sketch and label the growth curve for a population of microorganisms in a closed culture.
Correct curve sketched, time x axis, population size y axis, lag phase, exponential phase, stationary phase, death/ decline phase all labelled.
Describe the lag phase of the bacterial growth curve.
The population does not grow quickly. Reproduction rate = death rate.
Explain the lag phase of the bacterial growth curve.
Population is small and is adjusting to new conditions - taking up water / cell growth / synthesising proteins.
Describe the log / exponential phase of the bacterial growth curve.
The population grows quickly. Reproduction rate > death rate.
Explain the log / exponential phase of the bacterial growth curve.
Population has adjusted; microorganisms have enzymes they need; sufficient space and nutrients.
Describe the stationary phase of the bacterial growth curve.
The population becomes static / no population growth. Reproduction rate = death rate.
Explain the stationary phase of the bacterial growth curve.
Nutrients and space are running out; waste is accumulating.
Describe the death / decline phase of the bacterial growth curve.
Population begins to fall. Reproduction rate < death rate.
Explain the death / decline phase of the bacterial growth curve.
Nutrients run out; concentration of waste products becomes toxic.
Give 1 / 2 / 3 steps you’d take to work aseptically.
Wash your hands, disinfect the working area, work near a Bunsen burner, flame the neck of any bottles upon opening and closing, only open the lid of the Petri dish enough to inoculate the plate, flame any glassware or metal equipment before use.
Explain why you’d work near a Bunsen burner when working aseptically.
The air warms and rises, preventing any air-borne microorganisms from settling / creates an area of sterile air in which the microbiologist can work.
What is meant by inoculation?
The deliberate introduction of microorganisms to a sterile medium.
How is the agar plate stored after inoculation?
Taped at 4 points, incubated at 25oC, placed upside down.
Explain the reasons for not sealing the lid to the agar plate using sticky tape after inoculation.
Allows oxygen to enter - preventing the growth of anaerobic pathogens.
Explain the reasons for incubating at 25oC after inoculation.
Incubating at 25oC prevents growth of pathogens.
Explain the reasons for storing the agar plate upside down after inoculation.
This prevents drops of condensation falling onto the agar; also prevents the agar drying out too quickly.
