From DNA to Proteins: How cells read the genome Flashcards
Gene Expression
Process where cells read out the instructions (nucleotide sequence) in their genes
What is the first step in gene expression?
Transcription
Portions of __________ are transcribed into RNA
DNA sequence
Transcription
Cells copy the nucleotide sequence of the gene into RNA molecule
RNA differs from DNA by containing _______ instead of thymine (T) in DNA (RNA has all the other bases like A, C, & G)
Uracil (U)
RNA
Is a linear polymer made of four different nucleotides (bases) linked together by phosphodiester bonds
The formation in genes that are expressed/ copied into RNA are done through the __________ since RNA is like DNA & can form complentary base pairs with A & U
Nucleotide Sequence
The structure of RNA is a large ________ molecule
Single - Stranded
Since RNA is a single-stranded molecule it can _______ into a variety of shapes
Fold up
_________ produces RNA that is complentary to one strand of DNA
Transcription
What is the process of transcription?
Begins by opening up a small portion of the DNA molecule & one of the two strands of the DNA molecule is used a template for making (synthesis) of RNA
The __________ of the RNA is based on the base pairing with the __________
Nucleotide sequence, the DNA template strand
What enzyme forms the RNA strand in transcription?
RNA polymerase
RNA transcript
The RNA chain that is produced by transcription
___________ is similar to RNA transcription
DNA replication
How does DNA replication differ from RNA transcription?
The RNA strand is removed from the complentary DNA strand (which allow DNA to re-form its double-helix structure)
Why is RNA only a single - stranded molecule?
Because its only transcribed from one DNA strand
RNA polymerase
Forms the RNA molecule (like DNA polymerase make DNA)
The _______ unzips the DNA strand & forms the RNA molecule in the 5’ to 3’ direction
RNA polymerase
Since RNA is _______ from DNA once its synthesis means that many RNA copies can come from the same gene (The synthesis of the next RNA is started before the first RNA is completed)
Removed
Unlike DNA polymerase in DNA replication, RNA polymerase can __________________
Start an RNA chain without a primer & doesnt proofread itself
Messenger RNA (mRNAs)
The RNA molecules that were formed by genes & also synthesis proteins (carry genetic information from the gene to make proteins)
_____________ refers to the process by which the information (the nucleotide sequence) of DNA is converted into a product either as proteins or RNA
Gene Expression
If the final product is a ________ then gene expression includes both transcription & translation
Proteins
If the final product is _________ then gene expression just requires transcription
RNA
When translating the nucleotide sequence into proteins, _________ & ________ are used
Ribosomal RNA (rRNAs) & Transfer RNA (tRNAs)
Ribosomal RNA (rRNAs)
Form the structural & catalytic core of the ribosomes which translate mRNAs into proteins
Transfer RNA (tRNAs)
Act as adaptors that select specific amino acids & hold them in place on a ribosome for their incorption into proteins
Signals in ______ tell the RNA polymerase where to _______ & _______ transcription
DNA, start & stop
To begin transcription ____________ have to be able to recognize the start of a gene & bind to that place
RNA polymerase
How does RNA polymerase recognize the transcription site in bacteria?
The RNA polymerase collide with the DNA molecule & weakly attach itself to move along the DNA strand till it finds a promter & once it finds the promoter it binds tightly to it & start transcription in front of the promoter
Promoter (start site)
Contains a specific sequence of nucleotides thats the starting point for RNA synthesis
What happens when the RNA polymerse finds the promoter?
- The RNA polymerase opens up the double - helix in front of the promoter where one of the two DNA strands acts as a template for complentary base - paring with the RNA formed by the RNA polymerase
- The RNA polymerase continues to make the RNA molecule till it reaches a second singal spot which is the terminator spot (stop site) where the the polymerase stops & releases the RNA strand
Bacteria promoter (start site) & the terminators (stop site) have ___________ that are recognize by the RNA polymerase (like AUG)
Specific nucleotides sequence
The _______ in bacteria is responsible for finding the promoter sequence in DNA & once it finds the promoter it binds to the DNA strand keeping it open
Sigma Factor
Since the RNA polymerase can only form the RNA molecule in the ____ to _____ direction it usuallly chooses the DNA strand that is in the 3’ to 5’ direction
5’ to 3’
What are the three types of RNA polymerase that are needed for translation in eukaryotic cells?
- RNA polymerase 1
- RNA polymerase 2
- RNA polymerase 3
RNA polymerase 2
Transcribes all the proteins
RNA polymerase 2 in eukaryotic cells can’t start transcription without the _____________
General Transcription factors
General Transcription Factors
Are accesory proteins that assemble on the promoter where they position the RNA polymerasse & pull apart the DNA double-helix to expose the template strand allowng the RNA polymerase to begin transcription (have a similar rol to the sigma factor in bacteria)
The process of a ______________ at a promoter begins by binding the general factor TFIID to a short segment of DNA that has mostly the bases of A & T (Its called the TATA Box)
General Transcription factor
Once the ______ is binded to DNA it serves as a landmark for other transfer factor proteins to assembly on the promoter
TFIID
Once the TFIID has binded to the _______ the other factors assemble along with RNA polymerase 2 to form a complete transcription initiation complex
TATA Box
Once RNA polymerase has been placed on the promoter it is released by the addition of ___________ to it “tails”
Phosphate groups
The action of adding ________ to RNA polymerase 2 is started by the general transcription factor TFIIH
Phosphate groups
Once RNA polymerase 2 is finished transcribing a gene its released from the DNA & its _____________ on its tail is stripped off by proteins called phosphatase
Phosphate groups (Only dephosphorylated forms of RNA polyermase 2 can be re-used to make an RNA molecule)
Eukaryotic mRNAs are made in the _________
Nucleus
__________ takes place in the nucleus of eukaryotic cells
Transcription
______________ occurs in the cytosol, so for eukaryotic mRNAs to be _________ into proteins they must be transfered out of the nucleus through small pores in the nuclear envelope
Translation, translated
Before the mRNA can be exported to the cytosol the eukaryotic RNA must go through what three processes?
- Capping
- Splicing
- Polyadenlation
The __________ responsible for RNA processing are on the phosphorylated tail of the RNA polymerase & are processing the RNA transcript as its being made
Enzymes
______________ of the tail of RNA polymerase 2 allows RNA processing proteins to assemble there
Phosphorylation
What two processes occur on an RNA transcript as its being processed into an mRNA?
- Capping
- Polyadenylation
Capping
Modifies the 5’ end of the RNA transcript (Also protects it from being degraded from certain enzymes)
Polyadenylation
Adding adenines to the end on the pre-mRNA to protect it from being degraded from certain enzymes
In eukaryotics, proteining coding genes are interrupted by non-coding sequences called ________
Introns
Introns
Its an intervening sequence that interrupts protein-coding
_________ are removed from pre-mRNAs by RNA splicing
Introns
RNA splicing
The introns are removed from the newly synthesized RNA & the exons are stitched together
Once the RNA transcripted has been ______ & its 5’ & 3’ ends have been modified the RNA is a fully functional mRNA molecule that can be translated into proteins
Spliced
RNA splicing is carried out by ___________
Small nuclear RNA (snRNAs)
Small nuclear RNAs (SnRNAs)
Recongize splice -site sequence through base-paring between their RNA components & the sequence in the pre-mRNA & carry out splicing
The ____________ form the core of the spliceosome
SnRNA (Small nuclear RNA)
Spliceosome
Is an assmebly of RNA & proteins molecules that carry out RNA splicing in the nucleus
An mRNA sequence is decoded/ read in sets of three nucleotides called _________
Condons
Translation
The converison of the information from RNA into proteins
The translation of mRNA into proteins depends on adaptor molecules called ______________
Transfer RNAs (tRNAs)
______ molecules match the right amino acid to the codons in mRNA
tRNAs
Transfer RNA (tRNAs)
Bind to a condon on one side & bind to an amino acid on the other side
Translation occurs in the ___________ of eukaryotic cells?
Cytoplasm
Translation of mRNA is driven by a _____________ where it reads the sequence on the mRNA
Ribosome
Anticodon
Set of three consecutive nucleotide that bind through base - pairing to the complementary codon in an mRNA molecule
The tRNA is an L shape where it has two regions: one forms the __________ & the other is where the __________ that matches the codon is convalently attached to the tRNA
Anti-codon, Amino Acid
For tRNA molecules to be an adaptor it must be linked to the right amino acid therefore it depends on ______________
Aminoacyl-tRNA synthetase
Aminoacyl-tRNA synthetase
An enzyme that convalently links each amino acid to the right set of tRNA molecules
Ribosomes
Is made of small proteins (ribosomal proteins) & RNA molecules called ribosomal RNAs (rRNAs)
Eukaryotic & Prokaryotic ribosomes are made up of one _________ & ________
Large subunit & Small subunit
The ___________ matches the tRNAs to the codons on the mRNA
Small subunits
The __________ forms the peptode bonds that linkl the amino acids together into a polypeptide chain
Large subunit
The two ______ come together on an mRNA molecule near its 5’ end to start the synthesis of a protein & as the mRNA moves forward in the 5’ to 3’ direction the ribosomes translate its nucleotide sequence(codons) into an amino acid sequence using the tRNA as adaptors
Subunits
What are the 3 binding sites in the ribosome?
- A site
- P site
- E site
What purposes that AUG serve?
- To tell the ribosomes to start translation
- To tell the ribosome to make methionine
Reading frame
Set of ordered triplets nucleotides (the codons)
Point Mutations
Simplest type of mutation (Can cause dieases)
Deletion
Loss of one or more bases
Insertion
Addition of one or more bases
Frameshift mutation
Inserting or deleting a base can cause a shift in the reading frame
Some tRNAs bind to more than one codon like a _________
Wobble
Wobble
A mismatch nucleotide pair (like G-U)
Exons
Smaller regions in the pre-mRNA & its what used to snythesis proteins