From Gene to Protein Flashcards
Are DNA molecules found in eukaryotes and prokaryotes the same?
Yes
What are genes?
sections of DNA containing information that is transcribed into RNA for proteins
What are genes?
sections of DNA containing information that is transcribed into RNA for proteins
What is the central dogma?
DNA is transcribed into RNA which is translated into an amino acid sequence
What is different about the structure of RNA and of DNA
-DNA is 2 stranded, RNA is one stranded
-RNA contains a ribose sugar and uracill instead of deoxyribose and thymine
What is the promoter region
Transcription start point situatied upstream (5’), RNA polymerase attaches there
Which direction does RNA polymerase read and write
Reads template srands in a 3’-5’ direction
Writes the RNA strand in the 5’-3’ direciton
What is the consensus nuelceotide sequence in prokaryotes
TATAAT positioned 10 base pairs upstream and serves as part of the promoter region
What is the second consensus nucleotide sequence in prokaryotes
TTGCCA 35 base pairs upstream of the transcription start point
What is the structure of RNA polymerase in prokaryotes
They have 1 type of RNA polymerase, a globular protein with channels running through it, with the active site where phosphodiester bonds are formed found at channel intersections
What are sigma factors
Found in prokaryotes, helps RNA polymerase bind to DNA at promoter regions
Binds with RNA polymerase to create a holoenzyme
What is a holoenzyme
Binds to and unwinds DNA
Made of RNA polymerase and sigma factor
How do incoming nucleotides attach themselves to the growing strand
-3’-OH separates phosphate bond from triphosphate, creating a phosphodiesterr bond between the incoming nucleotide and growing strand
-Two phosphates are released as pyrophosphate
What is a Rho-independent terminator sequence
-Contains inverted repeat followed by a string of 6 adenines
-Inverted repeats are transcribed and fold in on themselves into a hairpin loop
-This pauses RNA and releases the mRNA
What is a rho-dependent terminator sequence
-Uses a rho factor protein
-Binds to and uses ATP to move along RNA and unwinds it from DNA template
What allows rapid reproduction in prokaryotes?
-Transcription and translation can happen at the same time
-Processes happen in the same area due to lack of nucleus
What ar transcription factor proteins
-Found in eukaryote (instead of sigma)
-Helps RNA polymerase bind
what is RNA polymerase I
transcribes genes for rRNA
What is RNA polymerase II
transcribes mRNA for proteins
What is RNA polymerase III
transcribes genes for tRNA and small regulatory RNA molecules
How is RNA modified in eukaryotes to leave the nucleus
-5’ cap and poly A tail
What is a 5’ cap
-Attached when transcription begins
-7-methylguanosine
-Guanosyl enzyme attaches 5’ cap
What is a poly-A tail
-Attached to 3’ end of mRNA following polyadenylation sequence
-Once AATAAA is transcribed, mRNA is cleaved and poly(A) polymerase adds 150-200 adenines
How does the polyAtail and 5’ cap protect the mRNA
-Prevents ribonuccleasee enzymes from targeting phosphodiester bonds
-Helps with ribosome attachment
What kind of termination does RNA polymerase I use
similar to rho-dependent
What kind of termination does RNA polymerase II use
termination coupled with polyadenylation
What kind of termination does RNA polymerase III use
termination sequence similar to rho-independent
What are spliceosomes
Location of splicing, made up of 5 small ribonucleooproteins (snRNPs)
How does the splicing of introns happen
-RNA in spliceosomes recognizes and pairs with nucleotides at the ends of introns
-Cut end forms a loop
-New phosphodiester bond is formed between the 3’ upstream exon and 5’ downstream exon
why did Gamow decide there must be 3 nucleotides in a codon
1 would make no sense because there would only be 4 possible amino acids, 2 was also not enough becuase there would be only 16
How can there be 64 possible combinations yet only 20 amino acids?
Some codons code for the same amino acid, but no codons code for multiple amino acids
What did Nirenberg and Matthaei determine
-Put all components necessary for protein synthesis into tubes
-Only uracil resulting in only phenylalanine
-Uracil and cytosine alternating gave serine and leucine alternating
-Proved there are 3 nucleotides in a codon, more trials found other combinations
What is the template strand
-Non-coding
-Minus strand
-Antisense strand
-Complimentary to RNA
What is the non-template strand
-Coding strand
-Plus strand
-Sense strand
-Same code as RNA except for thymine
What does AUG code for
-Start codon
-Methionine
What are the stop codons
UAA
UAG
UGA
What is the open reading frame
sequence of a gene from the triplet start codon to the triplet stop codon
How many possible reading frames are there if a DNA molecule is unknown
6
What are the steps of prokaryotic protein synthesis
transcription-initiation-elongation-termination-translation
What are the steps of eukaryotic protein synthesis
transcription-initiation-elongation-termination-mRNA processing-RNA export-translation
What changes phenotype for hair colour
Amino acid variation in melanocortin receptors
Why does transgenics work
-The genetic code is shared almost universally
-There are genetic similarities but there are limitations
-Some species have the same codons, but they may code for different amino acids
What is retinoblastoma
cancer caused by disruption of Rb protein in eye
What does the Rb protein do
Regulates cell cycle (apoptosis)
If it fails, cancer/cell division occurs
Metastasis
cancer spreads through blood and lymphatic system to other areas
How does chemotherapty work
-Drugs travel via liposomes to areas of cancer growth to reduce cell division
-Inhibit topoisomerases needed to unwind DNA for replication
What makes triple -ve breast cancer aggressive
-Rapid spreading and cell diviison
-No estrogen and progesterone receptors making it difficult to treat via hormonal/lipid medicaiton
-Radiation and chemotherapy are the only current options
How can triple -ve breast cancer risk be determined
-Kaiso expression levels
-Prevalent in black and hispanic women
What is kaiso
-Transcription factor
-Regulates expression of how cells grow, adhere, and die
-Malfunction leads to tumours and agressive cancer spread
