Oncogenes and tumor suppressor genes
Methylation
Adding methyl group to promoter will inactivate tumor suppressors; parental imprinting-marked cytosines are just added methyl groups-->inactive allele
Sporadic retinoblastoma
a single tumor appears in one eye sometime in early childhood before the retina is fully developed and mitosis in it ceases
myc protein
acts as a transcription factor and it controls the expression of several genes
Tumor suppressors
genes whose protein products can directly or indirectly prevent cell division or lead to cell death; functions in regulation of transcription, DNA repair and cell-cell communication; inhibits mitosis; behaves as a recessive; anti-oncogenes
Proto-oncogenes
genes whose protein products stimulate or enhance the division and viability of cells; genes that contribute to tumor growth by inhibiting cell death
Ras gene products
involved in kinase signaling pathways that control the transcription of genes, which then regulates cell growth and differentiation
Familial retinoblastoma
multiple tumors in the retinas of both eyes occurring in the first weeks of infancy
Oncogenes
mutated proto-oncogenes; behaves as dominants; genes associated with the stimulation of cell division; cancers results from only one allele of gene
Transcription factors c-myc and c-fos
needed for mitosis-->cell division
Rb protein
prevents cells from entering S phase of the cell cycle by binding to a transcription factor (E2F)--> E2F can no longer bind to promoters of proto-oncogenes (c-myc or c-fos); anti-oncogenes
CpG Islands
stretches of alternating Cs and Gs
p53 protein
tumor suppressor gene; prevents a cell from completing cell cycle if its DNA is damaged or cell has suffered other types of damage; can pause cycle so it can be repaired properly; triggers cell suicide when necessary; anti-oncogenes
Loss of Heterozygosity
tumor suppressors are recessive-->one mutated gene will not effect cell. two mutated genes-->predisposed to develop into tumor-->deduction to homozygosity
Src protein
tyrosine kinase; alters several target molecules, resulting in the transmission of signals to the nucleus that help regulate the cell
