7. Genetic Changes over time

A population that shows several variants of a trait is most accurately described as

• polymorphic

• donomorphic

• dimorphic

• discontinuous

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Higher biological fitness is most likely linked to

• the likelihood an infertile organism will survive to old age

• the ability for an organism to compete with others for food

• the endurance of an organism

• the heterozygosity of an organism

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A population of land snails, Theba pisana, live on Rottnest Island in Western Australia. Compared with populations from the mainland, the island populations have significantly reduced genetic variation, with a decay of heterozygosity within the gene pool. The implication is that

• natural selection has over time chosen for a particular allele, causing homozygosity in the gene pool of the island T. pisana snails

• gene flow between island and mainland populations of T. pisana snails have caused the decrease in genetic diversity

• T. pisana snails from the early founder group to Rottnest Island did not carry a wide range of alleles

• T. pisana snails from the founder group were mainly heterozygous; however, selection pressures over time on the island caused directional change in allele frequencies

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A species of flowers in a small area of grassland produces seeds that can be occasionally swept by the wind to other grasslands. When these seeds germinate and become established in the new grassland, they can eventually pollinate flowers of the same species in that population. This scenario can be best described as an example of:

• the founder effect

• gene flow

• the Bottleneck effect

• allopatric speciation

It is hypothesised that if a population is infinitely large, allele frequencies will remain steady over time. However, most real-life examples of populations are finite in size and the allele frequencies can change dramatically in a short period of time. What is this dramatic change most likely due to?

• Natural selection

• Mutation

• Gene flow

• Genetic drift

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Which of the following is most likely to cause genetic variation in populations?

• Mutations that arise in somatic cells

• Silent mutations appearing in coding regions

• Missense mutations appearing in non-coding regions

• Independent assortment of homologous chromosomes during meiosis

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A coding region of a gene for an enzyme contains the following DNA sequence: TAC GGA TTT TTA ACA If a nonsense mutation occurred in this sequence, it is reasonable to assume that

• a different amino acid would be coded for in the peptide product for this gene

• there would be shape changes in the protein product for this gene, but the peptide would remain the same length

• the corresponding substrate would not be able to bind to the enzyme product

• due to the redundancy of the DNA code, there would be no difference in the peptide product for this gene

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Which one of the following scenarios best describes selective breeding?

• Farmers downsizing their flocks of sheep due to food supply shortages during drought

• Producing genetically modified tomatoes that do not become soft when ripening

• Euthanising a sick or wounded livestock animal

• Using oysters that have greater resistance to parasite infection for an oyster farm

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When medical devices are implanted into the human body, one particular risk is bacterial infection. This occurs when bacteria adhere to the implanted devices, forming a slimy layer known as biofilm. Antibiotics are a common form of treatment for these infections; however, many chronic infections persist with the rise of antibiotic resistant bacteria.

Here are a series of statements that describe the development of antibiotic resistance in bacteria:

1. Due to over-prescription of antibiotics, time is given for bacteria to adapt and become resistant.

2. When a full course of antibiotics is not taken, random mutations can occur giving bacteria resistance to the antibiotics.

3. Cell-to-cell contact between bacteria can result in the transferal of antibiotic resistant genes.

Which of these statements are true?

• Statements 1 and 2

• Statements 2 and 3

• Only Statement 1

• Only Statement 3

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Every year the Australian Influenza Vaccine Committee will make a recommendation for the composition of the influenza vaccine for the community. In 2020, three new strains were introduced. People are advised to have the new vaccine each year even if they have had the flu vaccine the year before because

• the mixing of genetic material between two viruses can create a new hybrid-type virus with increased virulence to which people will have no immunity.

• point mutations occur in the genetic material of the virus, causing small changes that a person will have no immunity to.

• antigenic drift occurs in several influenza virus strains, leading to new viral strains with new combinations of antigens.

• although people may have already had the vaccine the previous year, they will need boosters to tackle the increasingly virulent influenza strains.

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