MUTATIONS AND DISEASES

1 EJC H2 Biology T3W3 Mutations & Diseases Mutations & Diseases 1. Overview of Topic We have, thus far, learnt about the processes of DNA replication and cell division. These processes are fundamental in an organism’s life cycle as they ensure that normal cellular activities can be continually carried out by new cells which originate from existing ones. However, as with most systems, perfection is hard to come by. Gene mutations and chromosomal mutations occur in cells during DNA replication and cell division. Though there are repair mechanisms which can correct such errors in eukaryotes, in some cases, cells could still end up with such mutations. These mutations could manifest in the phenotypes of organisms and lead to diseases. In this chapter, we will be taking a closer look at the types of mutations which can occur in cells and examples of diseases which could be brought about due to these mutations. 2. Learning Outcomes a. Explain what is meant by the terms gene mutation and chromosome aberration. For gene mutation, knowledge of how substitution, addition, deletion could change the amino acid sequence (e.g. frameshift) is required. For chromosomal aberration, knowledge of numeral (e.g. aneuploidy, as in the case of trisomy 21, i.e. Down syndrome) and structure (e.g. translocation, duplication inversion, deletion) aberration is required. b. Explain how gene mutations can result in diseases (including sickle cell anaemia). 3. References Campbell, N.A. and Reece, J.B. (2008). Biology, 9th edition. Pearson. Jones & Jones. (1997). Advanced Biology. Hoh Yin Kiong (2003). Longman A-Level Course in Biology, Vol. 1. Longman Green, Stout and Soper (1990). Biological Sciences, Vol 1. Cambridge Raven, Johnson, Losos, Mason & Singer (2008). Biology, 8th edition. McGraw-Hill.

2 EJC H2 Biology T3W3 Mutations & Diseases Contents 1. Overview of Topic ...................................................................................................... 1 2. Learning Outcomes.................................................................................................... 1 3. References ................................................................................................................. 1 4. Gene mutations ......................................................................................................... 3 Example of disease: Sickle Cell Anaemia ................................ ................................ ........ 6 Example of disease: Cystic Fibrosis ................................ ................................ ................ 9 7. Chromosomal mutations ......................................................................................... 11 (I) Variation in the chromosomal structure ................................ .............................. 11 Examples of diseases: ................................ ................................ ........................