Studied by 2 peopleProteins in the ________ that lack signal sequences for destinations within the endomembrane system are usually secreted from the cell via vesicles that fuse with the cell membrane.
RER
Requires a promoter (special region of DNA to which the ________ binds) to tell ________ where to begin and which of the 2 strands to transcribe.
RNA polymerase
When not active in the ________ the ribosome exists as two separate subunits.
translation of mRNA
________ can technically start synthesizing anywhere, but DNA sequences and certain proteins tell ________ where to stand.
RNA
________ occurs when RNA polymerase catalyzes the formatio nof phosphodiester bonds between added nucleotides and the growing RNA chain, releasing pyrophosphate in the process.
Transcription
________ bind by hydrogen bonds and run antiparallel.
Codon & anticodon
________ A change in a genes sequence that changes the amino acid at that site in the encoded protein; usually causes a single amino acid change in the protein, which may or may not cause a change in function.
Missense mutations
________ read the DNA template in the 3 to 5 direction and synthesize the RNA strand in the 5 to 3 direction.
RNA polymerase
Helps export ________ from nucleus, bind proteins, and makes ________ stable.
mRNA
________ interrupt, but do not scramble, the DNA sequence of a gene.
Introns
TRNAs bind to particular ________.
amino acids
________ spliced out of pre- mRNAl 5 cap and 3 poly A tail added to mRNA.
Introns
When a(n) ________ is encoded by four codons, the first two letters are always the same.
amino acid
There is at least 1 specific tRNA molecule for each of the 20 ________.
amino acids
The synthesis of RNA using one strand of DNA as a template
Transcription
The synthesis of a protein (polypeptide); Takes place on ribosomes, using the information encoded in messenger RNA
Translation
The premise that information flows from DNA to RNA to polypeptide (protein)
Central Dogma of Molecular Biology
Most abundant RNA types
mRNA, rRna, and tRNA
Encodes protein information that comes from a template strand of DNA; leaves the nucleous
mRNA
One of the two strands of DNA that for a particular gene specifies the amino acids in a protein; Same base sequence as transcribed RNA but with Ts instead of Us
Coding Strand
The DNA strand that is transcribed to create an RMA transcript; Also refers to a strand of RNA that is used to create a complementary RNA
Template Strand
Several species of RNA that are incorporated into the ribosome; Involved in peptide bond formation
rRNA
A family of folded RNA molecules; each carries a specific amino acid and anticodon that will pair with the complementary codon in mRNA during translation; recognizes which amino acid needs to be added next
tRNA
a protein that binds to RNA polymerase, allowing the complex to bind to and stimulate the transcription of a specific class of genes
Sigma Factors
Proteins that assemble on a eukaryotic chromosome, allowing RNA polymerase II to perform transcription
Transcription Factors
The nucleotide sequences in a gene that directly specify amino acids in a protein
Coding Regions
A portion of a gene within the coding region that is transcribed into pre-mRNA but is spliced out prior to translation
Introns
A portion of a DNA molecule, in eukaryotes, that is present in the mature mRNA and codes for part of a polypeptide
Exons
The initial gene transcript before it is modified to produce functional mRNA; Also known as the primary transcript
Pre-mRNA
introns are removed, and both ends of the pre-mRNA are chemically modified
The primary transcript of a eukaryotic gene is modified in several ways before it leaves the nucleus
The last stage of RNA processing in eukaryotes, in which the transcripts of introns are excised through the action of small nuclear ribonucleoprotein particles (snRNP)
RNA Splicing
Short stretches of DNA that appear, with little variation, in many different genes
Consensus Sequences
A conserved sequence (A followed by several pyrimidines) in the interior of an intron that is used during intron splicing to attach the 5 end of the intron
Branch point
A complex of an enzyme and a small nuclear RNA molecule, functioning in RNA splicing
snRNPs
An RNA-protein complex that splices out introns from eukaryotic pre-mRNAs
Spliceosome
A chemically modified GTP added to the 5 end of mRNA; facilitates binding of mRNA to ribosome and prevents mRNA breakdown
5 Cap
A long sequence of adenine nucleotides (50-250) added after transcription to the 3 end of most eukaryotic cells
Poly A Tail
Three nucleotides in messenger RNA that direct the placement of a particular amino acid into a polypeptide chain
Codons
The set of instructions, in the form of nucleotide triplets, that translates a linear sequence of nucleotides in mRNA into a linear sequence of amino acids in a protein
Genetic Code
A sequence of three nucleotides in an mRNA that encodes a particular amino acid
Sense Codons
The mRNA triplet (AUG) that acts as a signal for the beginning of translation at the ribosome
Start Codon
An organism engineered to contain, and usually express, a gene from another organism
Transgenic organisms
When a DNA substitution alters the codon but does not alter the encoded amino acid; occur because of the degeneracy of the genetic code
Synonymous mutations
A change from a sense codon to a stop (nonsense) codon, causing a premature termination of translation and a shortened protein; usually also loss of function
Nonsense mutations
A change from a stop codon to a sense codon, causing additional amino acids to be added to the end of the protein; effects depend on how many amino acids are added to the end of the protein and how important that part of the protein is to function
Loss-of-stop mutations
The addition or deletion of a single or two adjacent nucleotides in a genes sequence; Results in the misreading of mRNA during translation and the production of a nonfunctional protein
Frame-shift mutations
The three nucleotides in transfer RNA that pair with a complementary triplet (a codon) in messenger RNA
Anticodon
certain bases in the third position of the anticodon are able to pair with more than just their normal partner
Wobble
highly specific enzymes that only bind to one amino acid and one corresponding tRNA, binds using energy
tRNA synthetases
initiation, elongation, termination
Three steps of translation
In protein translation, a combination of a small ribosomal subunit, an mRNA molecule, and the tRNA charged with the first amino acid coded for by the mRNA; formed at the onset of translation
Initiation Complex
The proteins involved in helping to assemble the translation initiation complex
Initiation factors
An RNA molecule with catalyctic activity
Ribozyme
The sequence within a protein that directs the protein to a particular organelle
Signal Sequence
Cutting a polypeptide chain; large polyproteins cannot function unless cut
Proteolysis
Addition of carbohydrates to proteins to form glycoproteins; helps direct some proteins to lysosomes, or help for conformation/regcognition functions at the cell surface
Glycosylation
the additon of phosphate groups to proteins, catalyzed by protein kinases; helps with cell signaling
Phosphorylation
• Used Neurospora (bread mold) to test hypothesis that specific gene expression → specific enzyme activity.
• All alleles are expressed as phenotypes.
• Wild-type strains have all enzymes to catalyze chemical reactions to make cell constituents.
• They treated wild type Neurospora with mutagens and isolated mutant strains that needed specific nutrient supplements to grow
• For each mutant strain, the addition of just one compound supported growth.
• Results suggested that each mutation caused a defect in only one enzyme in a metabolic pathway.
Beadle and Tatum
Translation in these species happens because the nuclear envelope separates transcription & translation.
DNA in nucleus, site of transcription
Ribosomes in cytoplasm (ER), site of translation
mRNA is the intermediate messenger
Eukaryotes
Translation occurs on growing mRNA for these species.
Prokaryotes
RNA polymerases can only add new nucleotides to the __________ of a growing strand.
3'
Transcription factors only occur in...
Eukaryotes
The template of DNA is TGACT. What is the mRNA (with start location)?
5' ACUGA
The mRNA is the same as the ______ end of _______, just replace T with U.
5', non-template DNA
This is added to the 5' end of pre-mRNA. Protects mRNA from being degraded and facilitates mRNA binding to the ribosome.
G cap
Added to the 3' end while processing ends of eukayotic pre-mRNA. May assist in export from nucleus.
Poly A tail
Start codon that initiaties translation.
AUG
Initiation signal for translation is near which end of mRNA?
5'
Stop codons that stop translation and polypeptide is released.
UAA, UAG, UGA
mRNA consists of...
5' cap, Start codon, exons, stop codon, poly a tail
Name for the start codon (AUG)
Methionine
The DNA template for arginine is 3' GCC 5' what is the codon within mRNA?
5' CGG 3'
The DNA template for arginine is 3' GCC 5' what is the anticodon on the tRNA?
3' GCC 5'
Three tRNA binding sites on the large subunit of the ribosome.
A site, P site, E site
During elongation, charged tRNAs enter the _______ site, large subunit acts as peptidyl transferase.
A
During termination, the stop codon enters the _________ site.
Termination
The bond is broken between the tRNA and its amino acid at the _______ site.
P
When the first tRNA has released its methionine, it moves to the ______ site and dissociates from the ribosome.
E
Note
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