Term
| a mutation is a .......... change in the DNA of a cell |
|
Definition
|
|
Term
true or false
a change in nucleotide sequence or change in gene position is a mutation? |
|
Definition
| true. mutations are rare and occur randomly. they are usually detrimental. |
|
|
Term
| which type of mutation is NOT passed onto offspring? |
|
Definition
| somatic mutations. these mutations are passed on to all the cells descending from the original mutant |
|
|
Term
| which mutations are passed onto offspring? |
|
Definition
| germ line mutations are passed on. |
|
|
Term
| name a benefit of mutation |
|
Definition
| it is the raw material from which natural selection produces evolutionary change. |
|
|
Term
| there are 3 types of base pair substitution point mutations. what are they? |
|
Definition
| silent, missense and nonsense. |
|
|
Term
| what is a silent mutation? |
|
Definition
| for example GGC codes for glycine but the C is replaced with a U but it is okay because GGU also codes for glycine |
|
|
Term
| what is a missense point mutation? |
|
Definition
| substitution to make a different amino acid. for example GGC is for glycine but the first G is replaced with A making AGC which is serine. this is a missense mutation |
|
|
Term
| what can the insertion or deletion of one base pair cause? |
|
Definition
|
|
Term
| why are frame shift mutations a pain in the ass? |
|
Definition
| they cause extensive missense (wrong amino acids being made) or nonsense (stop codon halting transalation) |
|
|
Term
| does the insertion or deletion of a 3 nucleotides cause a frameshift mutation? |
|
Definition
| no. it causes there to be one extra or one less amino acid but no frameshift mutation occurs. |
|
|
Term
| breakage of a chromsome can lead to 4 types of changes in chromosome structure. what are they? |
|
Definition
deletion
duplication
inversion
(reciprocal) translocation |
|
|
Term
| what happens in a deletion of chromsome? |
|
Definition
| a part of the chromsomal segment is removed. eg. removal of a part in the short arm of chromsome 5 results in cri-du-chat syndrome |
|
|
Term
| a chromsome duplication... |
|
Definition
| repeats a segment.. if it adds it near the original alleles it is known as a tandem. if it doesnt it is known as non-tandem. eg. charcot-marie tooth disease. progressive loss of muscle tissue and touch sensation, arched feet, curled toes. result of duplication on long arm of chromsome 17 |
|
|
Term
| when a chromosome fragment reattacthes to the original chromosome but in the reverse orientation is known as? |
|
Definition
| inversion. no specific conditions associated with inversions at present |
|
|
Term
| what happens in translocation? |
|
Definition
| a chromosomal fragment joins a nonhomolous chromsome. translocations can be reciprocal like Famillial downs syndrome (14:21) or Chronic myeloid Leukeamia (9:22) |
|
|
Term
| why can 5 bromouracil base pare with adenine and guanine? |
|
Definition
it is a tautomer. the keto form is complementary to adenine.
the enol form is complementary to guanine. |
|
|
Term
| what point mutation can 5 bromouracil induce? |
|
Definition
| changing a AT bp to a GC base pair |
|
|
Term
| spontaneous mutations can occur due to the inheritent instability of DNA what does this mean? |
|
Definition
nucleotides can change to other confirmations like isomers and tautomers thus during DNA replication an incorrect base is inserted to form mismatched pair.
eg, normal (amino) form of cytosine pairs with guanine but a tautomer of cytosine (an imino acid) pairs with adenine instead. |
|
|
Term
| spontaneous deamination of cytosine to uracil occurs in which condtions? |
|
Definition
| increased in acid conditions. |
|
|
Term
| what change would occur if replication proceeded with a deaminated C? |
|
Definition
| well normally cytosine pairs with guanine. when deaminated to uracil it results in A being inserted because Adenine pairs with uracil. thus daughter strand base pairing changed from CG to TA. |
|
|
Term
| what is the role of Uracil DNA glycosylase? |
|
Definition
| as uracil is not usually found in DNA, its role is to remove Uracil from DNA to prevent mutations |
|
|
Term
| what are chemicals that add hydrocarbon groups to nucleotide bases called? |
|
Definition
|
|
Term
| what does O-6-ethylguanine pair with? |
|
Definition
| thymine. the normal guanine pairs with cytosine. |
|
|
Term
| what effect does o-6-ethylguanine have on base pairing? |
|
Definition
| it changes a CG bp to an AT bp. |
|
|
Term
| which bases specifically absorb UV radiation? |
|
Definition
| the pyramidine bases tymine and cytosine |
|
|
Term
| what happens if two T or two C residues are adjacent to each other on the same DNA strand? |
|
Definition
| covalent bonds can form between them forming a cross link |
|
|
Term
| what is the cross link between adjacent pyramidines called? |
|
Definition
|
|
Term
| what is the affect of pyramidine dimers? |
|
Definition
| it blocks DNA synthesis leaving a gap opposite the site of damage. the gap is filled by alternative polymrases. |
|
|
Term
| what is different about the special alternate polymerases that fill the gap that pyrimidine dimers create? |
|
Definition
| they are special because they are able to fill this gap. however the base pairing is relaxed. |
|
|
Term
| how can thymine dimers be removed? |
|
Definition
| by nucleotide excision repair (NER) |
|
|
Term
| what is nucleotide excision repair? |
|
Definition
| broad specificity repair system that recognises distortions in the dna helix. |
|
|
Term
| how does nucleotide excision repair work? |
|
Definition
| a nucelase enzyme cuts the damaged DNA strand at 2 points. DNA polymerase fills the gap with new synthesis of nucleotides. DNA ligase seals the remaining nick. |
|
|
Term
| which 3 components are important in nucleotide excision repair? |
|
Definition
Nuclease enzyme - to cut the damaged DNA
DNA Polymerase - to synthesise complimentary strand
DNA Ligase - to seal the remaining nick. |
|
|
Term
| what is Xeroderma Pigmentosum? |
|
Definition
| a condition with deficiencey in nucleotide excision repair. thus development of skin cancer at early age but only to those parts of body exposed to the sun. |
|
|
Term
| name the disease in which cells escape from the control methods that normally regulate cell growth and division. |
|
Definition
|
|
Term
| when cells divide unchecked, they can give rise to tissue masses AKA? |
|
Definition
|
|
Term
| if a tumor cell stays together in a single mass it is said to be? |
|
Definition
|
|
Term
| if the cells of a tumor can invade and disrupt surrounding tissues it is said to be? |
|
Definition
| malignant. it is when it is identified as cancer |
|
|
Term
| cells from malignant tumors can break off, move through blood and lymphatic system emerging and forming tumors at other locations in the body. this is known as? |
|
Definition
|
|
Term
| what is the normal role of a proto-oncogene? |
|
Definition
| to stimulate cell division in a precisely controlled manner. |
|
|
Term
| how does a proto-oncogene transform into an oncogene? |
|
Definition
| a genetic chnage that leads to an increase in the proto-oncogene's protein or the activity of the protein. |
|
|
Term
| are oncogene mutations genetically dominant or recessive? |
|
Definition
|
|
Term
| how can viruses promote cancer development? |
|
Definition
| by intergrating their DNA into that of infected cells. |
|
|
Term
| name 3 ways a proto-oncogene can be transformed to an oncogene? |
|
Definition
translocation - gene in a new locus under new controls
gene amplification - multiple copies of the gene
point mutation - mutation transforming into an oncogene resulting in a resistant protein. |
|
|
Term
| what is the normal role of a tumor suppressor gene? |
|
Definition
|
|
Term
| how can mutations in tumour repressor genes contribute to cancer? |
|
Definition
| decrease in the normal activity results in loss of inhibition of cell division therefore more cell division takes place |
|
|
Term
| are mutations in tumor suppressor genes usually dominant or recessive? |
|
Definition
|
|
Term
|
Definition
| it is a G protein and a proto-oncogene. it is a component of a signal transduction pathway that stimulates cell cycle and division |
|
|
Term
| mutations in the ras proto-oncogene occurs in how many percent of human cancers? |
|
Definition
| 30%. this figure is higher in pancreatic and bowel cancers. |
|
|
Term
| what kind of mutation cause the ras proto-oncogene to send signals of its own? |
|
Definition
|
|
Term
| what is needed to activate the normal pathway of a ras proto-oncogene? |
|
Definition
| growth factor needs to bind and start a reaction cascade. when a mutation occurs, the ras oncogene doesnt rely on growth factors but issues signals of its own. |
|
|
Term
|
Definition
|
|
Term
| in the ras pathway where do the growth factors bind to? |
|
Definition
| tyrosine-kinase receptors |
|
|
Term
| what reaction does the RAS proto-oncogene set off? |
|
Definition
| a phosphorylation cascade in protein kinases. they eventually reach transcription factors which activate gene expression. |
|
|
Term
| what kind of gene is p53? |
|
Definition
|
|
Term
| how many % of cancers does mutations in p53 gene occur? |
|
Definition
|
|
Term
| is promoting the synthesis of growth-inhibiting factors the NORMAL or MUTANT job of te p53 gene? |
|
Definition
| the normal job thus a mutation that knocks out the p53 gene can lead to excessive cell growth and cancer |
|
|
Term
| normally when is the p53 gene expressed? |
|
Definition
| when there is damage to cells DNA. it promotes growth-inhibiting proteins so the damage can be repaired before the DNA is replicated. |
|
|
Term
| what other gene can p53 activate and what does this other protein do? |
|
Definition
| it can activate the p21 gene. this halts the cell cycle. |
|
|
Term
| name 3 things the p53 gene can do |
|
Definition
can activate p21 - halt cell cycle
turn on DNA repair genes - to fix damaged DNA
can initiate suicide genes when DNA is irreparable - leads to program cell death or apoptosis. |
|
|
Term
| in which ways do ras proto-oncogene and p53 differ? |
|
Definition
ras proto-oncogene is part of a system that stimuates cell division. its mutation causes it to become hyperactive.
p53 stimulates synthesis of growth inhibiting factors. its mutation makes its function ineffective resulting in unregulated cell division. |
|
|
Term
| how many cell division check points must be inactivated for cancer to initiate? |
|
Definition
|
|
Term
| cancer involves mutations in multiples genes and what else? |
|
Definition
at least 1 active oncogene and several tumor suppressor genes. most cancers occur over the age of 40
|
|
|
Term
| in mutations that commonly lead to colorectal cancer the first stage is the loss of APC. what is this? |
|
Definition
| APC is a tumor repressor gene. (Adenomatous polyposis coli) |
|
|
Term
| loss of APC allows growth of a small benign growth. what is this growth known as? |
|
Definition
|
|
Term
| in colorectal cancer what will activation of the ras oncogene do? |
|
Definition
| stimulate uncontrolled cell division as the ras oncogene is hyperactively sending signals to stimulate transcription factors. |
|
|
Term
|
Definition
| it is also a tumor suppressor gene called Deleted in Colorectal Carcinoma. the downfall of this results in a larger benign growth. |
|
|
Term
| what is the larger benign growth called in the stages to colorectal cancer? |
|
Definition
| adenoma. a benign tumor of glandular origin |
|
|
Term
| in colorectal cancer which is the last tumor supressor gene to be lost? |
|
Definition
| p53. this is when additional mutaions occur and the benign tumor becomes a malignant carcinoma. |
|
|
Term
|
Definition
| cancer that begins in the tissues that line the inner or outer surfaces of the body. |
|
|
Term
| altogether how many tumor suppressor genes are lost in the progression of colorectal canceR? |
|
Definition
| 3. first APC then DCC then P53. |
|
|
Term
| consolidate the steps of colorectal cancer. 5 steps. 3 losses of tumor suppressor genes and one activation of ras oncogene |
|
Definition
1. loss of APC (small benign growth polyp)
2. activation of ras oncogene (hyperstimulation of cell growth)
3. loss of DCC (larger benign growth, adenoma)
4. loss of P53 (additional mutations)
5. malignant tumor aka carcinoma |
|
|
Term
|
Definition
| causes cancer and reduces life expectancy |
|
|
