CP 12 Gene Structure Flashcards
Which direction is RNA made
5’ –> 3’, uses 3’–>5’ dna strand as template
the DNA bases are:
the RNA bases are:
ATCG
AUCG
what are the differences between DNA replication and Transcription
- Only 1/2 DNA nucleotide strands acts as template for synthesis
- Relatively small part of DNA molecule serves as template
- RNA polymerases catalyze assembly of RNA nucleotides into RNA strand
what are the 2 main parts of a gene
- regulatory region
- Coding region
what is the regulatory region of a gene
a promoter (control sequence for transcription)
what is the coding region of a gene
a transcription unit (section of the gene that is
copied into an RNA molecule)
what is the basic structure of a prokaryotic coding gene from left to right
- promoter
- 5’ UTR
- start codon
- DNA being coded
- stop codon
- 3’ UTR
- terminator signal
what is the basic structure of a eukaryotic coding gene from left to right
- promoter
- 5’ UTR
- start codon
- DNA being coded (Exon 1, Intron, Exon 2) separated by splice signals
- Stop codon
- 3’ UTR
- Poly(A) Signal
TF Eukaryotes have a termination sequence
F
what are the 3 steps to transcription
- Initiation
- Elongation
- Termination
what are the steps to initiation
- promoter binds (TATA Box)
- Transcription factors (TF) bind
- RNA polymerase 2 binds
- additional TFs bind to form “transcription initiation complex”
what are the steps to elongation
- RNA polymerase moves along the DNA, it untwists double helix
- gene can be transcribed simultaneously by several RNA polymerases
- Nucleotides are added to the 3’ end of growing RNA molecule
what are the steps to termination
- Complete RNA is released
- RNA polymerase leaves
- dbl helix reforms
In eukaryotes the RNA polymerase 2 is responsible for ____ while RNA polymerase 1 is responsible for ___
- tRNA, 1/4 rRNAs, protein coding genes
- the three other rRNAs
Whats the difference between transcription in prok and euk cells
- prokaryotes, mRNA produced by transcription is immediately translated without more processing
- In eukaryotes, nuclear envelope separates
transcription from translation
what is pre-mRNA
- beginning RNA template in euk cells that are modified through RNA processing to yield
finished mRNA - Must be processed in nucleus to produce translatable mRNA
what is the 5’ cap on mRNA
- Site where ribosome attaches to mRNA
- Connected by 3 phosphate groups
what is the Poly(A) Tail in pre-mRNA
- substitute for terminator sequence
- Signals RNA polymerase to stop transcription
- Protects mRNA from RNA-digesting enzymes
what are the Introns and exons of pre-mRNA
- Introns = Non–protein-coding intervening sequences in the pre-mRNA
- Exons = Amino acid-coding sequences retained in finished mRNAs
TF Exons have to be removed before translation
F, Exons are expressed
how many variations of genetic code can be made with a 3 letter codon
64
TF Each codon specified same amino acid in all living organisms
T
How many sense codons and how many stop/start codons are there
- 61 sense codons
- 3 stop/start
what is the “Wobble Hypothesis”
First two nucleotides of anticodon and codon must match exactly, Third nucleotide has more flexibility
what is aminoacylation
the process of adding the AAs to a tRNA
what are the 2 types of ribosomes
- Prokaryotic 705 Ribosome (505 top, 305 bottom)
- Eukaryotic 805 Ribosome (605 top, 405 bottom)
what are the sites of a Ribsosome (in order)
-A (aminoacyl site)
-P (peptidyl site)
-E (exit site)
what does the A site in a ribosome do
accepts the tRNA with the AA
What does the P site on the ribosome do
Base pairing between codon (mRNA) and anticodon (tRNA), binds their AA to the growing polypeptide chain
What does the E site of the ribosome do
Releases the tRNA without the AA attached
what happens in termination in translation
- A site reaches stop codon
- Release factor (RF) binds to A site
- Peptide chain released from P site
- Ribosome disassembled
what is a polysome
Multiple ribosomes simultaneously translate single mRNA
what is polypeptide processing (3 steps)
Processing convert polypeptides into finished form
- Removal of one or more amino acids from the protein chains
- Addition of organic groups
- Folding to get correct 3D structures
TF polypeptides can be inactive and activated at certain locations
T, (Pepsin inactive form pepsinogen activated by stomach acid removal of amino acids)
what are sorting signals
sort proteins to cellular locations where they function
TF cells cant adapt
F, cells need to adapt
what is one way that cells adapt
gene regulation
what is gene regulation
Ability of cells to control levels of gene expression
eg) Proteins produced at the correct time in the correct amounts
why is eukaryotic gene regulation necessary
- cell differentiation
- to turn certain genes on and off as organism matures (embryo –> adult)
what is the most common level of gene regulation if prokaryotic cells
transcription, sometimes translation, minimally at protein/post-translational level
what is a missense mutation
Sense codon changed to different sense codon
what is a nonsense mutation
Sense codon changed to nonsense (stop) codon
what is a silent mutation
Sense codon changed to different sense codon that specifies the same AA
what is a frameshift mutation
Single base-pair deletion or insertion in coding region of gene
