4.4 Gene Mutations and Cancer Flashcards
what is a gene mutation
a permanent change in the sequence of bases in DNA
-can have no effect to complete in activty
what are three causes of mutations
mutagens, errors in replication, transposons
describe errors in replication
rare, DNA polymerase enzym that carries out replication, proofreads new strand against old strand
-mismatched pairs then replaced with correct nucleotide
describe mutagens
mutagens: environmental influences include radiation (radioactive elements, X rays, UV radiation) and organic chemicals (smoke, pesticides)
- rate generally low because DNA repair enzymes constantly monitor and repair any irregularities
describe transposons
transposons AKA jumping genes: specific DNA sequences that have ability to move within and between chromosomes, movement to a new location sometimes alters neighbouring genes
-discovered in bacteria, fruit flies, humans
what are the effects of a point mutation
-involve a change in a single DNA nucleotide, could be a possible change in specific amino acid
what are the effects of a frameshift mutation
occur most often because one or more nucleotides are either inserted or deleted from DNA, can be completely new set of codons and nonfunctional protein
what is a metabolic pathway
-a single nonfunctioning protein can have a dramatic effect on the phenotype
-enzymes are proteins that control reactions in the cells, metabolic pathway: cell reactions that involved synthsis/breakdown operate togther, regulated by activty of a particular enzyme
ex. A to enzyme to B to eenzyme to C
if faulty code for enzyme then A cannot go to B then there will be a buildup of A
how does cancer develop
- series of accumulating mutations that can be different for each type of cnacer
- when tumour suppressor genes inactive and oncogenes are active, cell division ozzurs uncontrollably because a cell signalling path from membraneto nucleus no longer normal fuctioning
what are tumour suppressor genes
act as brakes on a cell division, esp when it begins to occur abnormally
what are proto-oncogenes and oncogenes
proto-ongogenes: stimulate cell division but usually turned off in fully differentiated non diviing cells
oncogenes: active proto-oncogenes that result from mutation
what are ras proteins and how can they cause mutations
proto-oncogenes code for ras proteins, needed for cells to grow, make new DNA, and not grow out of control
-a point mutation can turn a ras proto-oncogene into oncogene resulting in abnormal growth
what is benign and malignant
benign: not cancerous
malignant: cancerous and can spread
what is a common multistep progression of cancer
- most cancers begin as an abnormal cell growth benign and usually doesnt grow larger
- mutation causing abnormal cells to be unresponsive to inhibitng signals
- growth turns to be malignant
describe the characteristics of cancer cells
- unstable: mutationgenesis (mutation after mutation after)
- do not correctly regulate cell cycle: cancer cells continue to cycle through cell cycle, do not operate to stop cycle and allow to differentiate so rate of division and numbers increase
- escape signals for cell death: do not respond to internal signals to apoptosis (die), turn on enzyme telomerase that rebuild and lengthen telomeres “immortal”
- survive and proliferate elsewhere in body: metastasis and angiogenesis, rob normal tissues of nutrients and oxygens from other cells
