L.5 Transription, Translation & DNA Repair Flashcards Preview

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Flashcards in L.5 Transription, Translation & DNA Repair Deck (30)
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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.



Mutated genes that cause cancer by affecting the cell-cycle.



Migration of affected cell to distant locations, through the bloodstream or lymphatic system.



Oncogenes before they become mutated


Tumor suppressor genes

Genes that create tumor suppressors genes,


genes that regulate cell cycle and 

participate in DNA Repair

also known as 


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?

  1. Proofreading
  2. Mismatch pair
  3. Nucleotide excision repair
  4. 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


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




What do redundancy and Wobble (third base codon) do?

Allow mutationa to occur without effects in protein


What are the three-point mutation?

  1. Silent
  2. Nonsense
  3. 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


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

  1. A 7-methylguanylate triphosphate CAP to the 5' end
  2. A Polyadenosyl (Poly-A) tail is added to the 3' end
  3. Splicing is done by spliceosomes, introns are removed in a lariat structure.
  4. polycistronic genes in prokaryotes, different gene products from one gene.
  5. Alternative splicing by combining different exons


What RNA translates codon into correct amino acid?



How are ribosomes useful? 

Ribosomes are the location where translation happens.


What are the 3 stages of translation?


  1. Initiation
  2. Elongation
  3. Termination 


Describe what happens in the initiation stage 


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?

  1. Folding by chaperones
  2. Formation of quartenary structures
  3. cleave of proteins or signal sequences 
  4. Covalent addition of other biomolecules
    • phosphorylation
    • carboxylation
    • gycolylation
    • prenylation


 Describe covalent posttstranslational modifications i detail.

  1. Carboxylation
  2. glycosylation
  3. phosphorylation
  4. prenylation

  1. Carboxylation; addition of carboxylic acid groups, usually serve as calcium-binding sites
  2. Gycosylation: addition of oligossacharides as proteins as they pass through the ER and golgi apparatus to determine cellular destination
  3. Phosphorylation: addition of phosphate PO42- by protein kinases to activate or deactivate proteins; most common seen in serine, threonine and tyrosine.
  4. Prenylation: addition of lipid groups to certain memebrane bound enzymes