DNA, genes and the continuity of life
Examples in context
Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
Bioinformatics
Bioinformatics involves the construction, maintenance and use of databases to analyse the relationships in biological data, such as amino acid sequences or nucleotide sequences (ACSBL068). DNA and protein sequences can be mapped and analysed to compare genes within a species or between different species. One example of a bioinformatics project is the Human Genome Project, an international, collaborative research project which resulted in the publication of the full sequence of the human genome in 2003 (ACSBL073). The project was completed ahead of schedule, largely as a result of widespread international cooperation and advances in genomics and computing. The databases associated with the project are freely available via the internet, and this data is used extensively by the international scientific community.
A $1000 genome
A number of companies have announced that individuals will soon be able to access full genome sequencing for roughly $1000, enabling many more people to identify whether they have gene variants associated with genetic disease (ACSBL071). One potential application of this technology is the sequencing of all babies at birth, in order to enable doctors to identify genetic conditions and structure individualised healthcare, dietary and exercise regimes that will lead to better health. However there is significant concern about the risks in making this data so readily available, and the privacy issues regarding ownership and availability of sequences. Many groups are calling for safeguards to be implemented before whole genome sequencing becomes widespread, including legislation to protect personal privacy, regardless of how the sample was obtained (ACSBL070).
Genetically modified organisms
Genetic engineering to insert genes responsible for specific traits into plant and animal DNA is seen by some scientists as the next wave of advancement in agriculture, with the potential to increase crop yields and provide ways to grow crops on degraded lands (ACSBL074). A wide range of transgenic crops is currently on the market, some having been engineered to resist pesticides, insects and disease. Work is also underway on transgenic animals with engineered traits such as faster growth and the ability to produce pharmaceuticals. Critics fear that genetically engineered products are being rushed to market before their effects are fully understood. Concerns include possible health risks to consumers and the long term ecological impact of releasing engineered organisms into the environment, including the effects on non-target organisms, a speeding of the evolution of pesticide-resistant pest species, and the possibility of gene flow from crop species to weed species resulting in the emergence of ‘super weeds’ (ACSBL072).
Continuity of life requires the replication of genetic material and its transfer to the next generation through processes including binary fission, mitosis, meiosis and fertilisation
(ACSBL075)
DNA is a helical double-stranded molecule that occurs bound to proteins in chromosomes in the nucleus, and as unbound circular DNA in the cytosol of prokaryotes and in the mitochondria and chloroplasts of eukaryotic cells
(ACSBL076)
The structural properties of the DNA molecule, including nucleotide composition and pairing and the weak bonds between strands of DNA, allow for replication
(ACSBL077)
Genes include ‘coding’ and ‘non-coding’ DNA, and many genes contain information for protein production
(ACSBL078)
Protein synthesis involves transcription of a gene into messenger RNA in the nucleus, and translation into an amino acid sequence at the ribosome
(ACSBL079)
Proteins, including enzymes, are essential to cell structure and functioning
(ACSBL080)
The phenotypic expression of genes depends on factors controlling transcription and translation during protein synthesis, the products of other genes, and the environment
(ACSBL081)
Mutations in genes and chromosomes can result from errors in DNA replication or cell division, or from damage by physical or chemical factors in the environment
(ACSBL082)
Differential gene expression controls cell differentiation for tissue formation, as well as the structural changes that occur during growth
(ACSBL083)
Variations in the genotype of offspring arise as a result of the processes of meiosis and fertilisation, as well as a result of mutations
(ACSBL084)
Frequencies of genotypes and phenotypes of offspring can be predicted using probability models, including Punnett squares, and by taking into consideration patterns of inheritance, including the effects of dominant, autosomal and sex-linked alleles and multiple alleles, and polygenic inheritance
(ACSBL085)
DNA sequencing enables mapping of species genomes; DNA profiling identifies the unique genetic makeup of individuals
(ACSBL086)
Biotechnology can involve the use of bacterial enzymes, plasmids as vectors, and techniques including gel electrophoresis, bacterial transformations and PCR
(ACSBL087)
Continuity of life on Earth
Examples in context
Support materials only that illustrate some possible contexts for exploring Science as a Human Endeavour concepts in relation to Science Understanding content.
Evidence for evolution
Darwin proposed the theory of evolution by natural selection to refute Lamarck’s theory. He provided evidence for descent with modification (branching evolution) based on patterns in variation of domesticated and wild species, and patterns of species distributions in time and space (ACSBL069). Contemporary evidence for evolution comes from five main lines of evidence: paleontology, biogeography, developmental biology, morphology and genetics. Technological developments in the fields of comparative genomics, comparative biochemistry and bioinformatics have enabled identification of further evidence for evolutionary relationships (ACSBL068).
Human evolution – are we still evolving?
Theoretical models of natural selection do not account for culture and technology, which can alter selection pressures so that it is not necessarily the ‘fittest’ that survive to reproduce. This has caused some to ask whether human evolution is still occurring, particularly in Western societies post the significant cultural events of agriculture, the Industrial Revolution, modern medicine and mass transportation. However, new results from projects such as the 1000 Genomes Project indicate that the rapid increase in the human population (from roughly five million at the end of the last Ice Age to more than seven billion today) has generated an enormous amount of variation in the species (ACSBL068). Other localised studies point to fertility-related natural selection (ACSBL069).
Sustainable population size and reserve area
The notion of minimum reserve size to maintain ecological processes is an important focus of conservation planning, and includes consideration of biogeography and population dynamics. Estimating minimum reserve size for a target conservation species can involve the calculation of minimum viable population and consideration of the area required for each individual in that population, given species preferences for particular habitat and social dynamics within the population (ACSBL074). However, determination of reserve size must also consider the needs and attitudes of other stakeholders, including cultural and economic values of indigenous peoples, recreational and aesthetic values of the public, the capacity to protect, monitor and manage the reserve, and other factors (ACSBL070). An alternative to single large reserves may be a number of smaller reserves that are connected by ‘green corridors’ that enable fauna to migrate.
Life has existed on Earth for approximately 3.5 billion years and has changed and diversified over time
(ACSBL088)
Natural selection occurs when selection pressures in the environment confer a selective advantage on a specific phenotype to enhance its survival and reproduction; this results in changes in allele frequency in the gene pool of a population
(ACSBL090)
In additional to environmental selection pressures, mutation, gene flow and genetic drift can contribute to changes in allele frequency in a population gene pool and results in micro-evolutionary change
(ACSBL091)
Mutation is the ultimate source of genetic variation as it introduces new alleles into a population
(ACSBL092)
Speciation and macro-evolutionary changes result from an accumulation of micro-evolutionary changes over time
(ACSBL093)
Differing selection pressures between geographically isolated populations may lead to allopatric speciation
(ACSBL094)
Populations with reduced genetic diversity face increased risk of extinction
(ACSBL095)