Introduction to the mutations and genetic diseases

    • Mutations and genetic diseases is a core JC1 topic in H2 BIO A levels. This topic builds upon DNA replication and protein synthesis and outlines all the different types of mutations that can occur at DNA as well as chromosomal level. Each mutation type is accompanied with a discussion of an example of genetic disease which includes sickle cell disease and Down’s syndrome.
    • This topic lays the groundwork and is a primer to cancer, an example of a multigene disease. It is also a complimentary topic to both molecular techniques and the genetics of inheritance and variation.

    A selection of materials for mutations and genetic diseases

    Most common phrasing errors students commit during exams

    • Sickle cell disease is due to a mutation in the haemoglobin gene
    • A person heterozygous for Sickle cell disease has an A gene and an S gene
    • Hb becomes sickle shaped. Different RBC stick together forming sickle shaped RBC
    • The mutation changes the codon resulting in a different amino acid synthesised/produced

    Exam tips

    • In mosiacism, some cells have the mutations and others do not. This is in contrast to other genetic diseases where all cells carry the mutations. The earlier case is likely congenital and the latter inheritance from parental gametes.

    Questions and other matters

    • JOIN my classes so that you can have your questions answered. In addition, access TYS questions from different JCs in Singapore as well as my comments and recommended answers.
    • You can also register for my H2 BIO crash courses to get ready for exams. Here’s the SCHEDULE.
    • You may also be interested to know how to boost your performance for A levels.