Cancer CAQ

🩺 Cancer Created Tags Explaining how lack of control of cell division can result from changes in expression of tumour suppressor genes/porto- oncogene COMMON MISTAKES Question is asking how uncontrolled cell division is caused by decreased protein production meaning that protein still functional but less Question not asking how lack of controlled cell division can lead to cancer (cancer is needed to be able to mention gain in function or loss in function mutation Tumour suppressor genes Decrease in expression of tumour suppressor genes Ref to named example (p53) Result in fewer proteins NOT DEFECTIVE PROTEINS that inhibit cell division/ arrest cell cycle at checkpoints/ promote DNA repair/ promote apoptosis Cell would continue to divide/not undergo apoptosis even in presence of irreparable DNA damage As mutations accumulate and cell survives through many divisions, uncontrolled cell division may occur Porto-oncogenes Increase in expression of porto-oncogenes Ma y 27 , 2025 221 AM Cancer 1

Ref to named example (ras) Would result in more proteins that stimulate normal cell growth and cell division/inhibit cell differentiation/halt cell death Cell would divide excessively Explain how mutations affecting the two groups of genes involved in cell cycle regulation may lead to development of cancer Definitions Gene mutations occur when an insertion, deletion, substitution of bases lead to a change in nucleotide sequence of a gene Chromosomal aberration can be in the form of a change in structure of chromosomes or number of chromosome due to failure of sister chromatids to separately during anaphase I and II failure of homologous chromosomes to separate properly in anaphase I, resulting in non-disjunction Proto-oncogenes code for proteins that stimulate cell division Tumour supressor genes code for proteins that inhibit cell division Proto-oncogenes A gain of function mutation to proto-oncogenes such as Ras to give rise to oncogene causing the product coded for by the gene being hyperactive or produced im excess such as growth factors or promote progression of cell cycle A mutation of one of the two copies of proto-oncogene into an oncogene is sufficient to cause abnormal cell proliferation A proto-oncogene can be may be moved from its normal location in one chromosome to another, and be placed under the control of enhancers/ a more active promoter which stimulates cell division translocation where a section of chromosomes breaks off and attaches to a non-homologous chromosome Cancer 2

A point/gene mutation can occur in the promoter/ enhancer /silencer that controls proto-oncogene causing an increase in expression A point/ gene mutation can occur in the coding region/sequence/exons of the proto-oncogene, altering 3D conformation of the protein coded for such that it is hyperactive and resistant to degradation Tumour suppressor gene A loss of function mutation may occur to the tumour suppressor gene such as p53,