SCSA Human Biology Mutations
5 sample questions with marking guides and sample answers · Avg. score: 48.9%
The term ‘selectively-advantageous mutation’ means the mutation
provides a survival advantage in a particular environment.
will always be passed to the offspring.
is always changing to adapt to new environments.
provides a benefit to heterozygote individuals in populations.
Scientists have discovered a gene mutation that slows metabolism of glucose, giving people with the mutation a lower risk of developing diabetes.
Which statement best describes the effect of this new, favourable allele in a population?
Because most populations are resistant to change, the allele is unlikely to be passed on and it will eventually be lost from the population.
Since natural selection favours phenotypes that are better able to survive and reproduce, the new allele will increase in frequency over time.
As the new allele provides a survival advantage, it will take over in the population and any unfavourable alleles will be completely eliminated.
Since it produces a beneficial phenotype, every individual in the population will carry the allele within a few generations.
Species of the genus Homo do not possess the powerful jaw muscles commonly found in the genera Australopithecus and Paranthropus. According to the fossil record, this decrease in the size of jaw muscles coincided with changes in brain size. Scientists have discovered that both the reduction in the size of the jaw muscles and the change in brain size occurred due to mutations.
Describe the various types of mutations, identify the causes and describe how they can occur.
Explain how the example of the evolution of the unique hominin jaw illustrates the importance of mutations to evolution.
A mutation is a permanent change in the DNA code. Lactase persistence is the ability to digest lactose (the sugar found in milk) in adults. This ability is attributed to a mutation that became present in various gene pools between 2000 and 20 000 years ago. Only about 35% of the world's adults possess the mutation today and can effectively digest lactose.
Identify and describe the type of mutation that would be responsible for lactase persistence, considering that it has been maintained within the gene pool. Compare this type of mutation to mutations that are not passed to future generations.
Point mutations can alter the DNA code in a number of ways, one of these being a frameshift mutation. Explain what a frameshift mutation is and describe two other ways point mutations can alter the DNA code.
In farming populations, the allele frequency for lactase persistence can be as high as 96% whereas in non-farming populations the frequency is only 20%. Explain how natural selection could be responsible for this difference in allele frequency.
Lactase is an enzyme that breaks down lactose, the sugar found in milk. Most babies produce lactase in infancy and usually the gene is turned off as a person grows older. Around 10 000 years ago, a mutation occurred that prevented the gene from turning off, so many individuals continue to produce lactase into adulthood and are lactose-tolerant.
The mutation resulting in lactose-tolerance varies widely in frequency in human populations. Evidence suggests the mutation originally occurred in central Europe and spread to other parts of the world. It also shows that there are several other mutations that allow people to digest milk products in adulthood.
Identify and outline the process of how a mutation could move from one population to another.
Explain how, in some populations, the process of natural selection could lead to lactase production being maintained in adults.
The Polymerase Chain Reaction (PCR) technique and gel electrophoresis have enabled scientists to analyse DNA samples which have been used to provide evidence for evolution.
Explain how the combination of PCR and gel electrophoresis could be used to show that lactose-tolerance could be caused by different mutations.