Biology Exam questions

What is the function of mRNA and trp

The function of mRNA in the production of proteins includes:

• coding for proteins/enzymes involved in the synthesis of trp

• carrying a copy of the genetic code to the ribosome for translation OR to be read by tRNA after binding to the ribosome.

The function of trp in the production of proteins includes:

• being an amino acid/monomer for proteins

• contributing to the growing polypeptide chain OR overall 3D functional shape of proteins.

Outline the process by which CRISPR genome is converted into gRNA

DNA unzips, RNA polymerase binds and moves along template strand catalyzing addition of the free nucleotides. Uracil replaces thymine

Identify a limitation of the trp operon model and propose a way this limiation can be overcome

The model is simplistic and doesnt consider the effect on other molecules in the cell, research into other molecules can be taken

How is a model different from a controlled experiment?

Modelling represents a system that people already know and allows them to conceptualize it where as controlled epxeriment looks at the relationship between independent and dependent variables

Chlorophyll is concentrated in bundle sheath cells when C3 plants have chloropyll concentratd in mesophyll

With reference to leaf structure, explain how C4 plants facilitate the photosynthetic pathway

-The seperation of CO2 fixation in mesophyll and Calvin cycle in bundle sheath minimises photorespiration

-As bundle sheath cells are deep in leaf/not close to stomata and surrounded by mesophyll cells where CO2 is converted into malate

-They have limited oxygen exposure and high CO2 concentration making Calvin cycle more efficient

What characteristic would u expect to see that could differentiate C3 and CAM plants

CAM plants have a larger vacuole, where water and malate is stored

Compare and contrast the products of anaerobic fermentation with those of anaerobic respiration in humans

Fermentation produces ethanol and CO2 where anaerobic respiration in humans produce lactic acid, Both produce 2ATP and NAD+

Trastuzumab binds to HER-2 receptor on cancerous cells in breast tissue, what immune response occurs?

-The cell is flagged for destruction by cytotoxic T cells causinf apoptosis

-Chemotherapy drug enters cell inducing apoptosis

-Blocks growth factors preventing further cell division

-Blocks blood supply to tumours preventing oxygen and other nutrients from reaching the cells

Propose an advantage to the use of monoclonal antibodies over traditional cancer treatments

-They only target cancer cells leaving healthy cells untouched

-Fewer side effects improving quality of life

State and describe a structual feature of the skull that has allowed for increased cranial capacity

Reduced bow ridge / flatter face , has more room for frontal lobe / cerebral cortex

What is herd immunity and why is it so important?

-Herd immunity occurs when the majority of a population is immune to a disease, in this case through vaccination which limits the spread of the disease due to there being no viable hosts

-This is important because it protects individuals who cannot be vaccinated such as those with weakened immune systems

Explain significance of genetic variation in evolution

-Genetic variation is essential to evolution because variation in a populations genotype leads to variation in phenotype

-Variation and in phenotype leads to the selection of one phenotype over another, and this contributes to changes in allele frequences which contribute to evolution

Explain why highly conserved genes can be used to determine relatedness between species

-Highly conserved genes are genes that have remained largely unchanged across different species and are shared by major taxa groups, but with slightly different DNA sequences due to mutations over time

-By comparing the DNA sequences of these genes we can determine evolutionary relatedness as species with fewer differences in these sequences are likely to share a more recent commo

Describe the structure of insulin in terms of hierarchial levels of protein

• The primary structure is the sequence of the 21 amino acids in chain A, and the 30 amino acids in chain B.

• The secondary structure is the alpha helices that chains A and B are folded into.

• The tertiary structure is the irregular, 3D folding of each peptide chain, held in place by bonds (e.g. disulphide bridges).

• The quaternary structure is the combination of the two peptide chains to form the final protein.

Would the gene encoding for the production of the chain A peptide contain fewer of more than 63 nucleotides? Give two reasons for your answer

• It would contain more than 63 nucleotides (even though the peptide it codes for consists of 21 amino acids - 21 x 3 = 63).

• The gene includes a STOP and a START codon, which do not code for amino acids.

• During RNA processing, splicing occurs, which removes introns

(nucleotides) from the strand of mRNA, so the resultant mRNA strand is shorter than the original gene.

Recombinant plasmids can be used to artificially create insulin, briefly describe the steps in creating artificial insulin using bacteria, including the roles of restriction enzymes, plasmids, DNA ligase and antibiotics. (5 marks)

-The gene is isolated and cut using restriction enzymes that create complementary sticky ends.

• A plasmid vector is cut with the same restriction enzyme and combined with the insulin gene, allowing DNA ligase to seal the gene into the plasmid, creating a recombinant plasmid.

• The plasmid is incorporated into bacterial cells using a process such as heat shock or electroporation.

• The bacteria are then grown on an agar plate containing an antibiotic. Only bacteria that have taken up the recombinant plasmid, which contains an antibiotic resistance gene, will survive, allowing for separation from non-transformed bacteria.

• The successfully transformed bacteria express the insulin gene and so produce the human insulin protein, which is then extracted and purified.

d) Identify a potential source of error in this experiment and describe how this might be minimised. (2 marks)

• Variations in leaf disc age or thickness.

• This could be minimised by ensuring that all leaf discs came from the same leaf, and in a region of the leaf where there was uniform thickness.

OR

• Inconsistencies in light intensity.

• This could be reduced by using a light meter to measure light intensity, instead of just relying on distance from the lamp.

Describe two ways in which anaerobic respiration in a bacterial E.Coli cell would  differ from aerobic respiration in a human cell. (2 marks)

• In E. coli, anaerobic respiration occurs only in the cytosol and does not involve mitochondria, whereas aerobic respiration in human cells involves the mitochondria.

• In E. coli, two molecules of ATP are produced per molecule of glucose in anaerobic respiration, while in human cells, 30- 32 molecules of ATP are produced per molecule of glucose in aerobic respiration.

 Describe how a population of pathogenic bacterial E.coli may evolve resistance to penicillin based on the process of natural selection. (4 marks)

• Within the population of E. coli, there is genetic variation. This variation leads to some individuals, due to their genotype, being resistant to penicillin.

• The penicillin provides a selection pressure to the population, as it presents a challenge to survival that not all individuals can withstand.

• Those individuals with genetic resistance to penicillin have a selective advantage, and consequently, they are the only individuals who can survive and reproduce.

• The offspring of these individuals inherit the penicillin-resistant genes, so after only a short number of generations, the entire colony consists of bacteria that are resistant to penicillin.

Identify the two types of nucleic acids involved in gene expression

• tRNA: transports amino acids to ribosomes; complementary anticodon binds with the mRNA codon.

• mRNA: carries genetic material from the nucleus to the ribosome.

• rRNA: the structural component of ribosomes, which assembles proteins.

• DNA: carries the instructions for proteins; controls cell activities.

• RNA: carries genetic material from the nucleus and delivers amino acids to the ribosome.

Construct a diagram to outline transcription

Compare repression and attenuation

• Both methods inhibit the transcription of the trp structural genes.

• Repression blocks RNA polymerase from binding to the promoter, whereas attenuation causes RNA polymerase to detach from the DNA at the attenuator.

• Repression prevents transcription from starting, whereas attenuation prematurely stops transcription (once it has started).

• Repression relies on a repressor protein to bind to the operator, whereas attenuation relies on hairpin loops forming in complementary mRNA domains.

Identify hierarchical level of haemoglobin

-Quaternary

-Haemoglobin has both alpha and beta chains meaning it has two or more polypeptide chains joined together

Explain how scientists use CRISPR CAS9 technology to edit BCL11A gene

• A piece of sgRNA is designed that is complementary to the BCL11A gene.

• The sgRNA is combined with a Cas9 enzyme (to form a CRISPR Cas-9 complex) and then guides Cas9 to the BCL11A gene in the stem cell.

• Cas9 binds to the PAM sequence and cuts both strands of the BCL11A gene (forming blunt ends).

• As the stem cell tries to repair the cut in the DNA, mutations and/or random nucleotides are incorporated, knocking out the BCL11A gene.

Why is CRISPR Cas9 not always effective?

• The stem cell may repair the break (after Cas9 cuts the gene) without incorporating the additional nucleotides.

• A mutation may have occurred in the BCL11A gene, meaning the sgRNA is no longer complementary.

• The stem cells may not have taken up the CRISPR-Cas9 complex.

• Off-target edits may have occurred.

How are biofuels produced?

• Biomass is broken down and exposed to enzymes to convert it into glucose.

• In yeast, the glucose is used as an input for anaerobic fermentation, producing ethanol.

• The ethanol is distilled and purified.

Suggest strategies to contain outbreak

• Limit travel of people from affected regions/quarantining people who travel from affected regions in Colombia.

• Education campaigns about the suitable use of insect repellent, mosquito nets, or suitable clothing.

• Inspect and fumigate cargo entering Colombia/travelling from affected regions.

• Provide mosquito nets or fly screens to households in affected regions to control mosquito breeding.

 Explain how monoclonal antibodies would neutralize yellow fever when injected to a patient.

• Monoclonal antibodies would be created that are complementary to antigens of the yellow fever virus and, therefore, will bind to them.

• This prevents the virus from being able to enter host cells / prevents the virus from spreading / this attracts phagocytes to the virus, which will destroy the virus.

Define genetic bottleneck

• When a large portion of a population is eliminated due to a random event, causing a reduction in genetic diversity.

Explain why mtDNA would have been compared instead of amino acid sequences

• The genetic code is degenerate/redundant.

• Not all differences in nucleic acids/DNA/mtDNA would be visible if amino acid sequences were compared, due to silent mutations; Therefore, mtDNA is more accurate.

6D) Explain how the mtDNA results allow scientists to determine the evolutionary patterns of the three cheetah sub species.

• Scientists would have compared the number of nucleotide differences in the mtDNA of the three sub-species.

• As mutations occur at a relatively constant rate, the more differences in the mtDNA, the more distant the common ancestor.

• Asiatic and Southern African cheetahs would have fewer differences when their mtDNA was compared/North-East African cheetahs would have had more differences in their mtDNA when compared to Asiatic and Southern African cheetahs.

Provide two reasons why it is possible for the scientific understanding of the ancestry of H. sapiens to change over time.

• The human fossil record is incomplete.

• Hominin fossils are scarce.

• The discovery of new fossils may require scientists to revise / change their previous hypotheses.

• Some fossils are incomplete, or only very small fragments are found.

The A. deyiremeda fossils were found in Ethiopia, which is located in Eastern Africa. Scientists believe this is another piece of evidence that supports the ‘Out of Africa’ hypothesis, which proposes that modern humans evolved in Africa and then migrated to other parts of the world, where they replaced earlier hominin species. Outline two pieces of evidence that would support this hypothesis.

• mtDNA evidence consistently demonstrates that the lineages of modern humans can be traced back to a common ancestor in Africa.

• The majority of older hominin fossils are found in Africa.

• The greatest genetic diversity of modern humans is found in African populations.

9B) Discuss the purpose of the two different sets of test tubes

• The set of test tubes without the inhibitor is the control set.

• The control set is used to ensure the results are due to the addition of inhibitor X, and not another variable / act as a baseline for comparison for the experimental test tube.

Identify one limitation of the experimental design and suggest how it could be improved.

• Only three concentrations of ADP + Pi were measured (5, 10, 25 millimoles) / the concentrations of ADP + Pi did not increase evenly (5, 10, 25), meaning there is a potential gap in the data.

• To improve, a wider range of ADP + Pi concentrations should be tested, with evenly spaced increments (e.g. 5, 10, 15, 20, 25 millimoles).

Explain why CRISPR- Cas9 can be highly specific when targeting genes, compared to the traditional use of endonucleases.

• Specificity of CRISPR-Cas9 results from the precise base pairing that scientists can determine between the guide RNA and the target DNA sequence, while other endonucleases are restricted to their specific recognition site.

• This allows for the target gene to be edited at any point using CRISPR- Cas9, rather than only at points that correspond to the recognition sites of restriction enzymes (as with other endonucleases).

The editing of human embryos raise ethical questions, describe the consequences based approach to bioethics and using this approach evaluate the use of CRISPR CAS9 in human embryos to treat cystic fibrosis.

• The consequences-based approach evaluates whether an action is right or wrong based on its outcomes, aiming to maximise overall benefits and minimise harm.

• A benefit of this treatment includes preventing a serious genetic disease / improving quality of life for individuals and families.

• However, a risk of this treatment includes unintended off-target mutations / ethical concerns about misuse, such as non-therapeutic enhancements.

• Given that the overall benefits of CRISPR-Cas9 in human embryos to treat a debilitating condition such as cystic fibrosis are likely to outweigh the potential harms and risks, it could be argued that a consequences-based approach may be used to ethically approve this treatment.

Describe one key structural difference between prokaryotic and eukaryotic genes and explain why this difference allows attenuation in prokaryotes but not eukaryotes.

• Prokaryotic genes do not contain introns, whereas eukaryotic genes contain introns that must be removed in RNA processing.

• In prokaryotes, transcription and translation occur simultaneously, which is necessary for attenuation to occur.

• In eukaryotic cells, the processes of transcription and translation occur separately in different parts of the cell (preventing attenuation), allowing for RNA processing to occur, which includes the removal of introns.

Describe the ethical concept of respect and suggest how this concept may apply to the use of DNA testing in paternity cases.

• Respect involves acknowledging the rights, autonomy, and dignity of individuals.

• In paternity testing, this may include ensuring that informed consent is obtained from all individuals and that confidentiality is maintained.

Describe the role of the lymphatic system in mounting an immune response.

• The lymphatic system transports immune cells, such as antigen- presenting cells, and antigens throughout the body in lymph vessels.

• Lymph nodes filter lymph fluid are the sites where antigen recognition occurs and where clonal selection and expansion also occur.

Explain how the Galapagos finches provide evidence for allopatric speciation.

• The finch populations were geographically isolated (a feature of allopatric speciation) on different islands, preventing gene flow.

• Over time, genetic differences accumulated between the populations due to different selection pressures, leading to the formation of new species.

Describe how the Howea palms provide evidence for sympatric speciation.

• They provide evidence for sympatric speciation because two species evolved in the same location, but became reproductively isolated by differences in flowering time and soil preference rather than geographical barriers.

Explain how enzymes such as those coded by the genes within the trp operon catalyse biochemical reactions? (2 marks)

Enzymes have an active site complementary to specific substrate(s), which bind to that active site. Enzymes lower the activation energy required to convert substrates into products.

 State two roles of neutrophils in an immune response to N. meningitidis

-Migration to site of infection

-Release cytokines to attract other immune cells

-Phagocytosis of bacterium

-Release toxins/defensins toxic to bacteria

Explain one economic benefit relevant to the vaccination of pregnant women (2 marks)

  -reduced hospitalisations or emergency care or paediatric treatment

●      cheaper to vaccinate compared to treating preventable diseases

●      lowered risk of RSV or other infections/illness

●      reduced strain on government-funded healthcare programs or reduced burden on public health system

●      increased herd immunity preventing community spread of RSV

●      reduced maternal sick leave or less carer/partner absences from workplaces

●      improved long-term child health or reduction in child health/education support later in life.

Explain how monoclonal antibodies work to reduce the severity of RSV in infants (2 marks) 

-binding to (RSV) antigen (not binding to pathogen/protein)

●      agglutination of virus

●      neutralisation of virus or prevention of virus spread

●      opsonisation or attraction of phagocytes to RSV

●      activation of complement proteins

●      activation of natural killer or cytotoxic T cells (which could occur through bispecific monoclonal antibodies, mAbs)

●      delivery of drugs/treatment directly to pathogen-infected cells (conjugated mAbs)

●      reduction of symptoms/number of RSV/number of infected cells.

Identify the process responsible for these DNA differences and explain how this process contributed to the successful expansion of colonies. (3 marks) 

• Mutations.

·   Mutations cause the formation of new alleles in the honeybee genome by altering the base sequence of DNA.

·   Some of these alleles are highly beneficial, providing a selective advantage to individuals that have them, causing those with the alleles to have an increased likelihood of survival and reproduction, passing on favourable alleles to offspring, over generations producing entire colonies with the advantageous alleles which aids in successful expansion.

Explain the potential genetic change in the native bee population

●      the genetic diversity in the native bee population may decline as alleles may be lost

●      the native bee population may reduce in numbers, reducing its gene pool

●      individual native bees that cannot compete with the Asian honey bees are selected against and do not survive (or vice versa)

●      these native bees do not reproduce, so less advantageous alleles are not passed on and decrease in frequency.

Other than enzymes, name two molecules the photosynthetic cyanobacteria would require to produce oxygen

●      water

●      chlorophyll

coenzymes/NADP/ADP + P_i

 Describe the role of each of the molecules named in partb.i in the production of oxygen

●      water is split to form oxygen and load coenzymes/NADP/ADP + P_i

●      chlorophyll captures light energy to facilitate splitting of water and loading of coenzymes/NADP/ADP + P_i

●      coenzymes/NADP/ADP + P_i assist enzymes to function by transferring electrons/energy/hydrogen ions between reactions.

Explain how an enzyme catalyses the breakdown of a protein

●      speeding up the rate of reaction or lowering activation energy

●      the substrate binding to the complementary active site on the enzyme

●      breaking peptide bonds between amino acids.

Identify a limitation of the model of protein synthesis and suggest a possible solution to this limitation ( 2 marks )

Example of a limitation of the model

Example of a possible solution

●      Overly simplified, for example: −       portrayed as a linear sequence of events −       full complexity of process is not included (e.g. protein folding / gene regulation / alternative splicing) ●      Full genome/proteome not known in all organisms ●      New discoveries are made that do not fit the current model ●      One model cannot explain the different types of protein synthesis (prokaryotes vs eukaryotes)

●      Have several models / detailed descriptions ●      More research required / more advanced technology required ● Change/refine the model based on new findings

Describe an organism's ‘proteome’ and use this concept to explain how organisms achieve such diversity in cell types. Refer to intestinal epithelial and fat cells. (5 marks)

an organism’s proteome: all of the proteins produced by an organism.

The explanation of how organisms achieve such diversity in cell types then needed to reference both intestinal epithelial cells and fat cells, and could have included:

●      that genes code for proteins

●      a description of gene regulation

●      a description of alternative splicing

●      that mutations can occur that cause a different protein to be produced

●      that different cells produce different proteins

●      that different proteins fold differently.

Explain why photosynthesis is considered a biochemical pathway ( 3 marks ) 

●      the outputs of one reaction are the inputs of the next reaction

●      it involves a series of reactions (light-dependent stage and light-independent stage)

●      it involves enzymes (e.g. Rubisco) and/or coenzymes (e.g. ADP/ATP and NADP/NADPH)

●      it involves different reactions occurring in different locations (grana / thylakoid membrane and stroma)

●      it is regulated by availability of reactants / concentration of products / abiotic factors.

Explain why some barley seeds may not be transformed when using CRISPR-CAS9 technologies ( 2 marks ) 

●      not all seeds/cells incorporated the CRISPR-Cas9

●      the gene may not always be edited OR off-target editing occurred

●      Cas9 did not bind to the PAM sequence OR did not cut the gene

●      single guide RNA (sgRNA) was not complementary to the target gene OR there was a mutation in the target gene

●      the cell repaired the cut made by Cas9 without inserting the nucleotide.

 Identify two ways monoclonal antibodies help treat HER2-positive breast cancer ( 2 marks )

-Binding to receptor 

-Carrying chemotherapy drugs

-Osponising cancer cells

-Immobilising cancer cell spread

Describe two factors that contribute to emergence of new pathogens ( 4 marks) 

Factor	Description
Zoonosis OR increased proximity to animals OR wildlife trade	Animals passing on new pathogens to humans
Antigenic shift	Major mixing/reassortment of viruses
Climate/environmental change	The release of new pathogens (e.g. melting of polar ice caps)
Increased exploration/travel	Humans reaching uncharted areas and encountering new pathogens
Increased biotechnology	The risk of a new pathogen escaping

Explain what led to genetic diversity between distinct groups of trees ( 4 marks )

The genetic diversity between the two groups of E. salubris may have been due to:

●      initial variation in alleles/phenotypes

●      the two groups being exposed to different selection pressures (e.g. different levels of phosphorus in the soil)

●      the thinner leaf trees having a selective advantage for growing in soils with high phosphorus levels

●      reduced gene flow between the two groups

●      separate mutations accumulating in each group

●      reproductive isolation (as a result of flowering time / pollination).

Describe the role of Rubisco in C3 plants ( 4 marks)

-Rubisco is involved in the light independent stage of photosynthesis. 

-It catalyses the reaction between carbon dioxide and (RuBP) meaning that it maximises the efficiency of the reaction. 

-The reaction produces an unstable six-carbon compound that splits into two molecules of glucose (OR G3P), which are then used in subsequent light independent reactions to produce glucose.

State two advantages of using bacterial cells to produce human insulin

• Using bacterial cells allows human insulin to be produced on a large scale.

• Using bacterial cells allows human insulin to be produced in a cost-effective manner.

• Using bacterial cells ensures that the human insulin produced is biologically identical to naturally produce insulin.

Describe one advantage other than crop productivity and one disadvantage of using GMO and transgenic organisms in agriculture ( 2 marks )

• reduced environmental damage

• reduced reliance on chemical pesticides

• improved food security

• reduced loss of crops (due to the engineering of pest-resistant proteins)

• development of monocultures (which reduces genetic diversity and increases

vulnerability to disease or environmental change)

• gene flow to wild populations, causing superweeds (which are resistant to herbicides

and difficult to control)

• reduced food safety (due to corporate control of seeds and farming practices)

Describe two physical barriers that plants have to prevent pathogen entry

• Common wheat has waxy cuticles that form a waterproof layer on leaf surfaces, which prevents the entry of pathogens.

• Common wheat has cell walls composed of cellulose, which provides structural strength and acts as a barrier to pathogens.

• Common wheat has outer epidermal layers that act as a protective covering to block pathogens from entering the plant’s tissue.

Describe how antimicrobial compounds and phenolic compounds in common plants defend against fungal pathogens

-Common wheat plants produce antimicrobial compounds that inhibit or kill fungal pathogens by disrupting their cellular processes (such as by damaging membranes or interfering with metabolism). 

-They also produce phenolic compounds, which strengthen cell walls. Stronger cell walls can act as a barrier to infection and so can limit the spread of fungal pathogens. 

-These compounds can also act as toxins to fungal pathogens, which reduces the pathogens’ ability to grow and reproduce.

Describe how monoclonal antibodies work to treat infectious diseases such as measles

Monoclonal antibodies are laboratory-produced antibodies that bind to specific antigens

They are highly specific (meaning that they are less likely to affect healthy cells when compared with traditional treatments) and therefore allow treatment to be more targeted.

In the treatment of an infectious disease such as measles, monoclonal antibodies

(for example, any two of:)

• bind to antigens and neutralise viruses

• block molecules that cause inflammation

• mark a virus for destruction by the immune system.

Outline adaptive radiation and how the Galapagos finches demonstrate this concept ( 2 marks ) 

-Adaptive radiation is the diversification of a single ancestral species into multiple species that are adapted to different ecological niches. 1 mark

The Galápagos finches demonstrate this through the evolution of different beak types that are suited to different food sources.

 Outline limitations of using Galapagos Finches as a case study for evidence of evolution ( 2 marks)

The study of Galápagos finches has occurred over a relatively short time period and focuses on a very specific environment. 

Therefore, it may not fully represent evolutionary processes that occur across varying environments, different species or longer time periods.

Function of mRNA and trp

The function of mRNA in the production of proteins includes:

·       coding for proteins/enzymes involved in the synthesis of trp

·       carrying a copy of the genetic code to the ribosome for translation OR to be read by tRNA after binding to the ribosome.

The function of trp in the production of proteins includes:

·       being an amino acid/monomer for proteins

·       contributing to the growing polypeptide chain OR overall 3D functional shape of proteins.

What is the role of coenzymes?

The general role of coenzymes in biochemical pathways includes:

·       assisting enzymes in catalysing reactions OR lowering activation energy

·       cycling between loaded and unloaded forms

·       carrying energy (e.g. ATP)

·       carrying protons/hydrogen (ions) and/or electrons (e.g. NADH, FADH₂, NADPH).

Explain why a case study is an appropiate methodology for the WHO swine flu investigation

·       it contains a real-world situation / real-world data, which informs health bodies/scientists

·       analysis of the causes and consequences of current and/or past outbreaks can lead to plausible/timely recommendations to help manage future outbreaks.

·       fieldwork would require the WHO/scientists to have contact with the virus, which would potentially be unsafe

·       a controlled experiment may be difficult, as there are many unknown variables OR it may be perceived as unethical to infect / test on patients

·       a correlational study is not required, as the WHO already understands the relationships or associations between animal and human cases of swine flu.

Explain how PCR can be used to identify presencse of Q fever pathogen

Polymerase chain reaction (PCR) is used to amplify the pathogen DNA to identify or analyse it further through gel electrophoresis.

Explain how an antigenic shfit in a virus on Lord Howe island could pose a current public health threat

·       the small population could experience a rapid transmission of the virus due to close contact among residents/visitors

·       if a tourist became infected before containment, this could lead to an epidemic/pandemic

·       the limited healthcare infrastructure, due to isolation from the mainland, might create challenges in receiving vaccines / medical supplies / treatments

·       if no treatment existed OR current treatment was no longer effective, it would take time to develop antivirals

·       the efficacy of current vaccines varies, as some individuals could mount a stronger immune response than others.

Compare the photosynthetic pathways in C3 and CAM plants, explain how the adaptatios in CAM plants enable them to survive in hot/arid environments

Similarities between the photosynthetic pathways in C3 and CAM plants include:

·       Rubisco fixes carbon dioxide in the Calvin cycle

·       photosynthesis occurs in the same cell type (mesophyll cells)

·       the light-dependent stage is identical OR it occurs before the light-independent stage.

Differences between the photosynthetic pathways in C3 and CAM plants include:

·       in CAM plants, a different enzyme (PEP carboxylase) fixes carbon dioxide first

·       CAM plants have two stages of carbon fixation, whereas C3 plants only have one stage of carbon fixation

·       CAM plants fix carbon dioxide at night, whereas C3 plants fix carbon dioxide during the day

·       in CAM plants, carbon dioxide is stored in a C4 compound (malate), whereas C3 plants use carbon dioxide immediately

·       in CAM plants, the stomata are typically closed during the day, whereas stomata in C3 plants are usually open during the day.

The adaptations in CAM plants that enable them to survive in hot, arid environments include:

·       minimising photorespiration at high temperatures

·       closing stomata during the day to reduce water loss.

Genetic drift

A random event changes the allele frequency within a population

Bottle neck effect

when a random event drastically drops the population

Natural selection

for natural selection to occur variation must exist in a population leading to phenotypic differences and a new environmental selection pressure (predation, climate change, etc) must act on the population interfering with their ability to reproduce. In the variation an allele fit for the selection pressure is conferred an advantage so the organism interbreeds to increase the allele frequency and for the trait to be inheritable it must be in the germline cell.

Two types of mutations exist POINT MUTATIONS or BLOCK MUTATIONS

In Point mutations TWO TYPES EXIST a) SUBSTITUTION and b) FRAMESHIFT MUTATIONS

Silent mutations

 In silent mutations a single DNA base is changed but has no overall effect on the DNA or protein because of the degeneracy code of amino acids where many genes can code for the same amino acid.

Nonsense mutations

Nonsense mutations cause a single DNA base to change but this codon change codes for the stop codon prematurely ending translation

Missense mutations

Missense is the most dangerous type of mutation a single DNA base change can alter the entire function of the protein/polypeptide product, it’s further split into two types conservative and nonconservative

Conservative mutations

 In conservative the amino acid that was changed did not have a major impact on the entire polypeptide product because of similar chemical properties

Nonconservative mutations

non conservative the amino acid changed has different chemical properties therefore the polypeptide CANNOT perform its functions. 

Block mutation

IN block mutations there are large scale changes which affect the entire segment of a chromosome instead of single nucleotides

Deletion, inversion, translocation, duplication

Selective breeding

An artifical form of natural selection

1/ Individuals in a population vary genetically leading to different phenotypic expressions

2/ with direct human intervention an artificial selection pressure is pressed onto the animals ONLY ALLOWING ANIMALS WITH DESIRABLE TRAITS TO BREED. 

3/ The desired trait must be heritable so after the breeding population reproduces, the frequency of the allele increases.

How does bacterical resistance happen

Bacterial resistance occurs when bacteria with mutations or acquired resistance genes survive antibiotic treatment and reproduce, increasing the frequency of resistance in the population

Antigenic drift

Antigenic drift is the gradual mutation accumulation in viral genes of a virus changing its antigen surface

Antigenic shift

Antigenic shift is a sudden major change in a virus's surface antigens caused by the exchange or reassortment of genetic material between different viral strains.

Transitional fossils

TRANSITIONAL FOSSILS: Fossils showing the characteristics of both ancestral and descendant groups providing evidence of evolutionary change 

Its used as evidence for evolution as it shows how characteristics of changed over time

Index fossils

INDEX FOSSILS: Fossil from species that was widespread and existed for a relatively short period 

Used to determine the relative age of rock layers from different locations, if same index fossils is found in two rock layers , the layers are likely to be from the same period.

Relative dating

Relative dating; using stratigraphy to find the relative age of a fossil by examining strata layers 

Limitations; does not provide an exact age, index fossils are only useful for relative dating WHEN they have the acquired characteristics ( widespread, and lived for a short period of time)

Absolute dating

Absolute dating: Using isotopes radiation and their half lifes to determine the absolute age of a fossil 

Limitations: Requires suitable radioactive isotopes with appropriate half life

Homologous structures

Structures found in different species that look and function differently but shown to derive from a common ancestor.

evidence of DIVERGENT EVOLUTION, divergent evolution is the evolutionary process where two or more species accumulate enough genetic differences to be classified as different species. THIS OCCURS because of individual populations adapting to different environmental selection pressures or genetic drift 

Analogous structures

Analogous structures are structures to serve similar biological functions but arent derived from common ancestors

evidence of CONVERGENT EVOLUTION, where two or more distantly related species (w/o a common ancestor) independently develop similar traits to adapt to similar environments and selection pressure

What is molecular homeology

Molecular homeology is the study and comparison of molecular DNA or amino acid sequences to determine the relatedness between species and EVOLUTIONARY RELATIONSHIPS

Limitations of DNA /amino acid sequencing

-A limitation in DNA or amino acid sequencing is that even if organisms share similar sequences its not able to determine what that type of fossil was used for as function

-DNA can degrade over time 

-mutations occur randomly so they don't highlight evolutionary relationships accurately 

-DNA is VERY long

Advantages of mtDNA

-There is no recombination in mtDNA (mixing of DNA between homologous chromosomes during meiosis) because its only inherited from the mother meaning mtDNA remains unchanged from generation to generation 

-Mutation rate is higher, so for very closely related species mutation rate ensures there's enough DNA sequences to compare. 

-Very high number of mtDNA available

Mammals have

MAMMALS are endothermic, have a 4 chambered heart, mammary glands, fur on the body,

Primates have

PRIMATES have 3D binocular vision, flexible spine, locomotion, opposable digit, large cranium

Hominoid characteristics

Homonoids share similar characteristics such as Y5 molar lower jaw, lack of tail, broad rib cage and pelvis, short spine between ribcage and pelvis

Explain why seeds edited with CRISPR CAS9 may be advantegous over transgenic seeds

CRISPR-Cas9 edited wheat seeds do not have a gene from another species inserted into the genome.

This reduces unknown harmful effects on people OR reduces risk of disease OR improves public perception / increases consumption.