Cambridge Pre-U Syllabus - Cambridge International Examinations

Cambridge Pre-U Syllabus
1.6 Genes and protein synthesis
Content
The gene and genetic code
Protein synthesis
Control of gene expression
Inheritance and Mendelian genetics
Mutations
Genetic conditions
Learning outcomes
Candidates should be able to:
a) define a gene as a unit of inheritance or as an ordered sequence of nucleotides located at a particular
locus on a particular chromosome which codes for a particular protein, or in certain cases a functional or
structural RNA molecule. Discuss the limitations of the latter definition with reference to introns, exons
and promoters
b) describe the genetic code and discuss the extent to which it is true that the code is universal to all
organisms
c) explain protein synthesis in terms of transcription and translation including the roles of DNA, mRNA,
tRNA and ribosomes
d) describe, in outline, eukaryotic introns, exons and the splicing of mRNA
e) define the term proteomics and outline its importance to biomedicine (limited to diagnosis and drug
design)
f) describe, in outline, the control of gene expression (limited to the lac operon in prokaryotes)
g) state, with examples, the differences between continuous and discontinuous variation (limited to relative
number of genes and alleles involved and relative impact of the environment as well as relative range of
phenotypes)
h) define and use the terms allele, locus, phenotype, genotype, dominant, recessive and codominant
i) use genetic diagrams to solve dihybrid crosses, including those involving sex linkage, autosomal
linkage, epistasis, codominance and multiple alleles
j) use and interpret the chi-squared test to test the significance of the difference between observed and
expected results. (The formula for the chi-squared test will be provided.)
k) explain that the effects of ionising radiation on living cells can have a range of outcomes including DNA
damage which is repaired, DNA damage that cannot be repaired, leading to apoptosis, and DNA
damage causing mutations. Mutations that do not kill the cell but are passed on to its descendants
during cell division (including mutations that can cause cancer e.g. those that cause proto-oncogenes to
become oncogenes and those that reduce the activity of tumour-suppressor genes)
l) describe gene mutations, limited to substitution, deletion and insertion
m) explain, with reference to sickle cell anaemia, cystic fibrosis and hereditary haemochromatosis, how
gene mutations might affect expression of a protein and thus affect phenotype (issues related to genetic
conditions need to be handled with sensitivity)
n) describe the causes and outline the symptoms of hereditary haemochromatosis (HH) as an example of
a recessive genetic condition (reference should be made to HFE protein)
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