pathology 4 Flashcards
describe the roles of G1, S, G2 AND M phase
G1 - growth phase
S- DNA synthesis & replication
G2- growth phase also prep for mitosis
M- mitosis occurs
what external factors are involved in the cell cycle control?
hormones
growth factors
stroma
cytokines
what helps control the cell cycle? give example
checkpoints , such as the restriction point (R) just before G1 phase
what are the 3 phases of interphase in the cell cycle?
G1
S
G2(G0)
if nutrient supply is inadequate what checkpoint does the cell cycle stop at?
stops at G1
if cell size is inadequate what checkpoint does the cell cycle stop at?
G1 or G2
what makes up the cell cycle checkpoints?
enzymes
specifically a catalytic sub-unit activated by a regulatory sub-unit
What are the catalytic sub-units in cell cycle checkpoints?
cyclin dependent kinase (CDKs)
what are the regulatory sub-units in the cell cycle checkpoints?
cyclins
what is the active cell cycle complex called when referring to checkpoints/name of checkpoint when cyclin binds to CDK?
CDK/cyclin complex
what two things regulate Cyclin dependent kinase activity ?
CDK inhibitors
production/destrcution of cyclins
what does retinoblastoma gene code for?
codes for protein called pRb
what does the protein pRb do?
inactivates E2F transcription factor which puts a brake in the cell cycle
what are carcinogens?
nongenetic factors that can lead to cancer
know the 3 types of environmental carcinogens
-chemicals
-radiation
-oncogenic viruses (hep 4,herpes)
what do you call a section of DNA attached to a chemical carcinogen?
DNA adduct
radiation carcinogens damages which part of the DNA?
targets purines & pyrimindine bases
how does mutated retinoblastoma gene cause cancer?
overactive E2F transcription factor
Dysregulation at which checkpoint causes most Cancers?
G1- S checkpoints
what is the role of p53
maintain genomic integrity
how does p53 work
p53 builds up in damaged cells
-cell cycle will arrest at G1 to help with DNA repair
-severe cases p53 induces apoptosis
what happens if p53 is mutated?
there is no G1 arrest or DNA repair
causes neoplasm to occur as damaged cells proliferate to form those
how many autosomal and sex determining chromosomes is in the human genome?
22 autosomal pairs
1 sex determing pair
what are the 3 stages of the cell cycle?
interphase, mitosis, cytokinesis
what are the 2 key regulatory molecules that determine progression through the cell cycle?
cyclin-dependant kinases (CDKs)
cyclin
what are the 2 families of CDK inhibitors?
INK4a(p14 and p16)
CIP/KIP(p21,p21 and p57)
what is the role of p14 in the cell cycle?
prevents p54 degradation
role of p16/INK4a?
binds to CDK4 which arrests the cell cycle at G1
what is p21 activated by?
p53
what state is pRb when active?
hypophosphorylated
what are the 3 genes that p53 can activate?
p21 (CDK inhibitor, G1 arrest)
GADD45(DNA REPAIR)
BAXX (apoptosis)
what do genotoxins cause?
irreversible genetic damage by binding to DNA
what are tumour suppressor genes?
genes that protect a cell from forming cancers
what causes chemical carcinogens to occur?
oxidation of purines and pyrimidines in DNA
what causes radiation carcinogenesis to occur?
UVB light causes thymine pairs to bond together into thymine dimers
