Biology Module 5
Name the type of cell division that produces four genetically different haploid cells.
What is meiosis?
Name a permanent change in the nucleotide sequence of DNA.
What is a mutation?
Name the type of pathogen that can reproduce only inside a living host cell.
What is a virus?
Name the process that maintains a relatively stable internal environment despite external change.
What is homeostasis?
Identify the variable that is deliberately changed by the investigator.
What is the independent variable?
Explain why DNA replication must occur before mitosis.
So each daughter cell receives a complete and identical set of genetic information.
Distinguish between a point mutation and a chromosomal mutation.
A point mutation changes one nucleotide or a small DNA sequence; a chromosomal mutation alters the structure or number of chromosomes.
Distinguish between an antigen and an antibody.
An antigen is a molecule recognised as foreign that triggers an immune response; an antibody is a specific protein made by B-cell-derived plasma cells that binds to that antigen.
State the roles of the receptor and effector in a negative-feedback system.
The receptor detects a change from the set point; the effector produces a response that opposes the change.
Distinguish between reliability and validity in an investigation.
Reliability is the consistency or repeatability of results; validity is whether the method tests the stated aim by controlling other variables and measuring what it intends to measure.
In pea plants, tall (T) is dominant to short (t). Predict the phenotype ratio from Tt x Tt.
What is 3 tall : 1 short?
Explain how exposure to an antibiotic can lead to a resistant bacterial population.
Resistant variants survive the selection pressure, reproduce and pass resistance alleles to offspring, increasing their frequency.
Explain how vaccination can produce a faster secondary immune response.
Vaccination exposes the immune system to antigens and forms memory cells, which rapidly produce a larger specific response during later exposure.
Explain how insulin lowers blood glucose concentration after a meal.
Insulin increases glucose uptake by cells and promotes conversion of glucose to glycogen, lowering blood glucose toward the set point.
A student measures enzyme activity at five temperatures. Identify the most suitable graph type and where each variable belongs.
What is a scatter or line graph, with temperature on the x-axis and enzyme activity on the y-axis?
A woman who is unaffected by an X-linked recessive condition has an affected father. She has children with an unaffected man. What proportion of their sons is expected to be affected?
What is 50%?
A population has allele frequencies p = 0.7 and q = 0.3. Under Hardy-Weinberg conditions, calculate the expected frequency of heterozygotes.
What is 0.42 or 42%?
A disease has a basic reproduction number, R0, of 4. Calculate the minimum herd-immunity threshold using 1 - 1/R0.
What is 0.75 or 75%?
A study finds that people who exercise regularly have a lower incidence of cardiovascular disease. Explain why this correlation alone does not prove that exercise caused the difference.
Other variables may differ between the groups, participants may not have been randomly allocated, and correlation does not exclude confounding factors or reverse causation.
A result is far from the other repeats. Describe what the student should do before deciding whether to exclude it.
Check for recording or procedural error, repeat the measurement, compare it with the full dataset and exclude it only with a documented scientific reason.
A DNA template strand reads TAC GGA CTT. State the mRNA sequence and the three amino acids produced.
What is AUG CCU GAA, producing methionine-proline-glutamic acid?
Evaluate one benefit and one biological risk of using CRISPR-Cas9 to edit a human embryo.
Benefit: it may prevent transmission of a serious inherited disorder. Risk: off-target or unintended heritable changes could affect the individual and future generations.
A new respiratory disease is spreading. Evaluate the combined use of isolation, contact tracing and vaccination as a control strategy.
Isolation reduces transmission from known cases; contact tracing identifies exposed people; vaccination reduces the susceptible population and future spread. Together they interrupt several points in the chain of infection, but effectiveness depends on timely detection, high participation and vaccine effectiveness.
Assess the use of genetic testing to predict a person's risk of a non-infectious disease.
It can identify inherited susceptibility and support early monitoring or prevention, but many diseases are polygenic and influenced by environment, so predictions are probabilistic. Privacy, discrimination and psychological impacts must also be managed.
Two treatments have means of 18.2 and 19.1 units, but their error bars overlap substantially. Evaluate the claim that Treatment B is more effective.
The mean is higher for B, but the overlap indicates considerable uncertainty and the graph alone does not establish a statistically significant difference. More replicates and an appropriate statistical test are needed.