Genetics is the study of genes. It is the study of heritability and how genes, and therefore physiological traits, are inherited. The discipline was founded in the late 19th century when Gregor Mendel showed that traits in pea plants were passed down through generations and that they seemed to follow particular laws. We now know that these inherited traits are determined by genes.
Genes are encoded within our DNA and hold all the instructions for growth and development. They determine every aspect of our being, from physical traits such as height and weight, to the ability to resist disease. They also play a role in establishing our behaviour and personality. But what exactly are these complex molecules?
This article provides a basic understanding of genes and their function in our lives, and gives an insight into the types of genetic research being undertaken in New Zealand.
What are genes?
Genes provide all the information a living being needs to grow and survive. They are the blueprints for proteins, which do all the jobs to maintain a cell, a tissue and therefore a whole being; every single cell in our body is a myriad of different proteins, performing different functions, which have been encoded for by genes.
Genes are made up of DNA, and in the nucleus of a human cell DNA is compartmentalised as 46 chromosomes. There are an estimated 20,000-25,000 protein-coding genes in humans; this is only about 1.5% of the total DNA [1]. The remainder is made up of regulatory sequences, introns and so-called non-coding DNA. Scientists used to believe that one gene coded for one protein, but we now know that one gene can code for several different proteins, albeit in a slightly different form.
Nature versus Nurture
This is an historical debate. General consensus today is that our growth, body responses and behaviour are a consequence of both genetics (nature) and environmental factors (nurture). It is clear just by looking at some individuals that appearance and physique have a strong genetic basis, but are other traits such as intelligence and personality purely genetic, or are these affected by our environment?
An example of the importance of innate versus learned responses is the learning of language. This is a completely learned response and children raised in linguistically-lacking environments have been shown to have under-developed language skills. However, it is our genes that dictate our ability to learn language at all [2]. A completely innate response is mammalian feeding – newborn mammals automatically know how to feed, regardless of maternal teaching.
Caspi in 2003 asked “why stressful experiences lead to depression in some people but not in others” [3, 4]. The evidence was compelling – that individuals with a short form of the gene 5-HT T (part of the serotonin transporter) exhibit more depressive symptoms and suicidality than those with a long version of the same gene. This is a striking example of how an individual’s response to the environment is mediated by genes.
Conversely, our environment can alter our genes. External factors such as ultra-violet light, radiation or certain chemicals can all cause the delicate structure of DNA to break down. Sometimes this can result in changes in gene expression which may lead to disease, such as certain types of cancer. Most disease states are a complex interaction between several (or many) genes, and are strongly influenced by the environment we live in, thus we can see that it’s the interaction between nature and nurture that determine our physical state.How are differences in DNA detected?
When genes mutate, gene expression goes awry and disease can occur. The relationship between genes and disease is a focal question in much genetic research and one of the main ways to investigate genetic differences in disease is by DNA sequencing. DNA is isolated from an individual, usually from their white blood cells, and a gene of interest is replicated many times in an enzyme-mediated reaction. Once the gene is isolated, this product is entered into a machine which tells scientists the exact DNA sequence of the gene. This can be analysed in reference to other sequences from other individuals, and deviations from the ‘normal’ DNA sequence can be identified.
Sometimes these changes have no adverse effect on the resulting protein of that gene. But if these changes alter the structure, and therefore the correct function, of the protein, associations may be made between that genetic variant and the disease in question, pending further investigation.
DNA sequencing is a very powerful tool that is widely and routinely employed in genetics laboratories, and is used to study not just genes and disease, but genetics in agriculture, horticulture and conservation as well.
What genetic research is going on in New Zealand?
New Zealand universities engage in a diverse range of genetic research. Centres of excellence include the Maurice Wilkins Centre at the University of Auckland [5, 6], which investigates the genetics of pathogens such as Mycobacterium tuberculosis and Staphylococcus aureus to determine how they are pathogenic to humans [7] as well as research into the genetics of neurodegenerative disease [8].
The genetics of premature ovarian failure in humans [9] is researched at the School of Medicine at Auckland. The Allan Wilson Centre for Molecular Ecology and Evolution [10] is composed of researchers from Auckland [5], Canterbury [11], Otago [12], Victoria [13] and Massey [14] universities, and is a government Centre of Research Excellence. It leads research into the evolution and ecology of New Zealand’s biota using molecular genetics [15-17].
The University of Otago has, amongst other specialities, a strong focus on medical genetic research. Current research includes pharmacogenetics, namely how a patient’s response to treatment is moderated by their genes [18, 19], the genetics of depression [20], and world-class research into the genetics of cancer [21, 22]. Biochemists are investigating the role of genetics on the function of cytochrome c, a molecule involved in cell stress and damage [23].
Genesis Research and Development [24] is an independent research organisation that is using genetics to investigate treatment of cancer and immune disease [25, 26].
The Department of Conservation [27] supports genetic research into the conservation of native New Zealand species. Through the use of genetics to characterise populations of animals and plants, conservation management strategies can be developed to protect species under threat [28, 29].
Biosecurity is maintained in New Zealand by the utilisation of genetic technology to research weed and pest population dynamics and the relationship a pest has with its host, and gene function in model pest insects is explored to better understand their pathogenicity (AgResearch [30] and HortResearch [31]). Nutrigenomics, the customisation of food based on the genetic profile of a patient, is a new and emerging field of genetic science in New Zealand (HortResearch).
Genetic technologies that characterise gene function in plants and enable selective breeding for targeted desirable traits are used in horticulture (Crop and Food Research [32]). Agriculture is enhanced by genetics that improve health therapies for livestock, and genetic diagnostics that allow animal selection for disease control (AgResearch). New Zealand also has independent companies using genetics in artificial insemination and selective breeding, for example, Brenco Livestock Genetics [33] and Genetic Enterprises Ltd [34], to name just two.
Summary
The broad range of research themes that employ genetic knowledge to their work is extensive and we can see that genetics is fundamental in human and animal health research. In order to protect ourselves and our biota from disease and disability, genetic research to investigate the biology of disease and health is crucial, both for us and for our flora and fauna.
This paper was reviewed by Associate Professor Martin Kennedy, of the University of Otago’s Carny Centre for Pharmacogenomics, Christchurch.
References
1. International Human Genome Sequencing Consortium, Initial sequencing and analysis of the human genome. Nature, 2001. 409: p. 860-921.
2. Ridley, M., Nature via Nurture: Genes, Experience, & What Makes Us Human. 2003: Harper Collins.
3. Caspi, A., et al., Influence of Life Stress on Depression: Moderation by a Polymorphism in the 5-HTT Gene. Science, 2003. 301(5631): p. 386-389.
4. Rutter, M., T.E. Moffitt, and A. Caspi, Gene-environment interplay and psychopathology: multiple varieties but real effects. Journal of Child Psychology and Psychiatry, 2006. 47(3-4): p. 226-261.
5. University of Auckland. http://www.auckland.ac.nz/.
6. Maurice Wilkins Centre. http://www.mauricewilkinscentre.org/index.php?page_id=68&PHPSESSID=ebb324b218b5e7a4438666cd9ec4a206.
7. Ramsland, P.A., et al., Structural basis for evasion of IgA immunity by Staphylococcus aureus revealed in the complex of SSL7 with Fc of human IgA1. PNAS, 2007. 104(38): p. 15051-15056.
8. Hodges, A., et al., Regional and cellular gene expression changes in human Huntington’s disease brain. Hum. Mol. Genet., 2006. 15(6): p. 965-977.
9. Chand, A.L., et al., Functional analysis of the human inhibin {alpha} subunit variant A257T and its potential role in premature ovarian failure. Hum. Reprod., 2007. 22(12): p. 3241-3248.
10. The Allan Wilson Centre for Molecular Ecology and Evolution. http://awcmee.massey.ac.nz/index.htm.
11. University of Canterbury. http://www.canterbury.ac.nz/.
12. University of Otago. http://www.otago.ac.nz/.
13. Victoria University Wellington. http://www.victoria.ac.nz/home/default.aspx.
14. Massey University. http://www.massey.ac.nz/.
15. Michel, C., et al., Distinct migratory and non-migratory ecotypes of an endemic New Zealand eleotrid (Gobiomorphus cotidianus) – implications for incipient speciation in island freshwater fish species. BMC Evolutionary Biology, 2008. 8: p. 49.
16. Irimia, M., D. Penny, and S.W. Roy, Coevolution of genomic intron number and splice sites. Trends in Genetics, 2007. 23(7): p. 321-325.
17. Steeves, T.E., M.L. Hale, and N.J. Gemmell, Development of polymorphic microsatellite markers for the New Zealand black stilt (Himantopus novaezelandiae) and cross-amplification in the pied stilt (Himantopus himantopus leucocephalus). Molecular Ecology Resources, 2008. 8(5): p. 1105-1107.
18. Roberts, R.L., et al., A common P-glycoprotein polymorphism is associated with nortriptyline-induced postural hypotension in patients treated for major depression. The Pharmacogenomics Journal, 2002. 2: p. 191-196.
19. Taylor, D.R., et al., Bronchodilator response in relation to beta-adrenoceptor haplotype in patients with asthma. Amer. J. Resp. Crit. Care Med., 2005. 172: p. 700-703.
20. Joyce, P.R., et al., Age dependent antidepressant pharmacogenomics: polymorphisms of the serotonin transporter and G protein beta3 subunit as predictors of response to fluoxetine and nortriptyline. Int. J. Neuropsychopharm., 2003. 6: p. 339 – 346
21. Guilford, P., et al., E-cadherin germline mutations in familial gastric cancer. Nature, 1998. 392(6674): p. 402-405.
22. Reeve, A.E., et al., Insulin-like growth factor-II imprinting in cancer. 2002. 359(9323): p. 2051.
23. Morison, I.M., et al., A mutation of human cytochrome c enhances the intrinsic apoptotic pathway but causes only thrombocytopenia. Nature Genetics, 2008. 4(4): p. 387-389.
24. Genesis Research and Development Corporation Limited. http://www.genesis.co.nz/.
25. Craig, H., et al., Y-box factor YB1 controls p53 apoptotic function. Oncogene, 2005. 24(56): p. 8314.
26. Delcayre, A., et al., A genome-based functional screening approach to vaccine development that combines in vitro assays and DNA immunization. Vaccine, 2003. 21(23): p. 3259-3264.
27. Department of Conservation. www.doc.govt.nz.
28. Chan, C.-h., et al., Conservation genetics of the Forbes’ parakeet (Cyanoramphus forbesi) on Mangere Island, Chatham Islands. DOC Research & Development Series no.254, 2006.
29. Hofstra, D.E., C.E.C. Gemmill, and M.D. Winton, Preliminary genetic assessment of New Zealand Isoetes and Nitella using DNA sequencing and RAPDs. Science for Conservation no.266, 2006.
30. AgResearch. http://www.agresearch.co.nz/.
31. HortResearch. http://www.hortresearch.co.nz/.
32. Crop and Food Research. www.crop.cri.nz.
33. Brenco Livestock Genetics. http://www.brenco.co.nz/.
34. Genetic Enterprises Limited. http://www.geneticenterprises.co.nz/.