L.5 Transription, Translation & DNA Repair Flashcards
6.4, 7.1 - 7.3
Cancer cells
Cancer cells are cells that divide relentlessly, forming solid tumors or flooding the blood with abnormal cells.
Cell division is a normal process used by the body
for growth and repair.
Oncogene
Mutated genes that cause cancer by affecting the cell-cycle.
Metastasis
Migration of affected cell to distant locations, through the bloodstream or lymphatic system.
Protooncogenes
Oncogenes before they become mutated
Tumor suppressor genes
Genes that create tumor suppressors genes,
by
genes that regulate cell cycle and
participate in DNA Repair
also known as
antioncogenes.
Mutation in tumor suppressor genes can also cause cancer
How do the alleles of the oncogenes and antioncogenes, explain their function.
oncogenes are esentially dominant, only one affected allele is needed to change a protooncogene to an oncogene.
Tumor supressor genes also only need one alle to work
What are the 4 types of repair mechanisms of DNA?
- Proofreading
- Mismatch pair
- Nucleotide excision repair
- Base excision repair
Proofreading happens in what phase of the cell cycle and what key enzymes/genes aid.
S pahse, DNA polymerase
Durring replication , DNA polymerase proffreadsits work and excises incorectly matched bases.
Daughter strand is ID by lack of methylation.
Mismatch Pair happens in what phase of the cell cycle and what key enzymes/genes aid.
G2, genes MSH2 MLH1
Detect and remove errors in replication that were missed during S phase.
Nucleotide excision repair happens in what phase of the cell cycle and what key enzymes/genes aid.
Excision endonuclease, G1 & G2
UV —> thymine dimers
Thymine dimers —–> distort double helix
NER—-> cut and patch process, removing affected oligonucleotide and DNA ligase seals
Base Pair Excision Repair happens in what phase of the cell cycle and what key enzymes/genes aid.
G1, G2 & Glycosylase enzymes and AP endonuclease
Thermal energy —-> C to U by loss of amino group
Small non-helix-distorting mutations system recognize
Glycosylase enzymes remove this U
and
replaces with AP site
AP site recognized by AP endonuclease
which removes it, then
DNA polymerase and ligase fill the gap
Central dogma?
DNA —-> RNA —-> Protein
What is a degenerate code?
A code that allows multiple codons to encode
for the same Amino Acid.
What are the initiation and Stop Codons?
Initiation: AUG
Stop: UAA, UGA, UAG
What do redundancy and Wobble (third base codon) do?
Allow mutationa to occur without effects in protein
What are the three-point mutation?
- Silent
- Nonsense
- Missense
Silent: mutations with no effect on protein synthesis
Nonsense: Mutation that inserts a stop codon
Missense: Mutation that produces a codon that codes for different Amino Acid
Describe frameshift mutations
A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read.
Difference between RNA and DNA
RNA
Ribose vs deoxyribose
Uracil vs Thymine
Single-stranded vs Double-stranded
What are the 3 types of RNA and their function?
Messenger RNA (mRNA)
Carries the message from DNA in the nucleus via transcription of the gene; it travels into the cytoplasm to be translated. 1 mRNA = 1 protein
Transfer RNA (tRNA)
Brings amino acids and recognized the codon on the mRNA using it anticodon
Ribosomal RNA (rRNA)
Makes up ribosome and is enzymatically active, catalyzes the formation of peptide bonds and aids in splicing
In transcription what is the role of Helicase?
Helicase unwinds DNA
What polymerase in transcription binds to TATA BOX?
Polymerase II binds to TATA BOX or promotor region to begin synthesis of hnRNA
What are 5 post-transcriptional modification
- A 7-methylguanylate triphosphate CAP to the 5’ end
- A Polyadenosyl (Poly-A) tail is added to the 3’ end
- Splicing is done by spliceosomes, introns are removed in a lariat structure.
- polycistronic genes in prokaryotes, different gene products from one gene.
- Alternative splicing by combining different exons
What RNA translates codon into correct amino acid?
tRNA
How are ribosomes useful?
Ribosomes are the location where translation happens.
What are the 3 stages of translation?
- Initiation
- Elongation
- Termination
Describe what happens in the initiation stage
Eukaryotes
40S Ribosome attaches to the 5’ cap and scans for a start codon: it lays down methionine in the P site of the ribosome.
initiation Factors
Charged initiators bind to start codon
What happens in elongation?
Involves the addition of a new aminoacyl-tRNA
into the A site of the ribosome and transfer of the growing polypeptide chain from the tRNA
in the P site to the tRNA in the A site of the ribosome.
What happens in termination?
Occurs when the codon in the A site is a stop codon, a release factorplaces a water molecule on the polypeptide chain and thus release the protein.
What are the 4 types of posttranslational modifications?
- Folding by chaperones
- Formation of quartenary structures
- cleave of proteins or signal sequences
- Covalent addition of other biomolecules
- phosphorylation
- carboxylation
- gycolylation
- prenylation
Describe covalent posttstranslational modifications i detail.
- Carboxylation
- glycosylation
- phosphorylation
- prenylation
- Carboxylation; addition of carboxylic acid groups, usually serve as calcium-binding sites
- Gycosylation: addition of oligossacharides as proteins as they pass through the ER and golgi apparatus to determine cellular destination
- Phosphorylation: addition of phosphate PO42- by protein kinases to activate or deactivate proteins; most common seen in serine, threonine and tyrosine.
- Prenylation: addition of lipid groups to certain memebrane bound enzymes
