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