8.4 Study Guide Flashcards
What is DNA Translation?
The process of using messenger RNA (mRNA) to build proteins.
Define: Codon
a sequence of three nucleotides in a DNA or RNA molecule that codes for a specific amino acid during protein synthesis
Define: Anticodon
Ensures the appropriate Amino Acid is inserted in the polypeptide
a sequence of three nucleotides that matches a codon in messenger RNA (mRNA) during protein synthesis. The anticodon is located on transfer RNA (tRNA).
How does an anticodon work?
- The cell transcribes DNA into a temporary copy of mRNA.
- The mRNA is read by the ribosome, which matches the codons in the mRNA to the anticodons in the tRNA.
- The tRNA delivers the amino acid that corresponds to the codon to the ribosome.
- The amino acid is added to the growing polypeptide.
- The process continues until a stop codon in the mRNA signals the end of protein synthesis.
What is Gene Expression?
The process by which the information encoded in a gene is turned into a function
Define Transcription
The process where a cell copies a specific section of DNA information into a molecule called RNA
Define: Translation
the biological process where the genetic information stored in DNA is converted into a protein by reading the sequence of messenger RNA (mRNA) and assembling amino acids into a polypeptide chain
Changes from nucleic acid language to amino acid language
Define: Start Codon
a sequence of three nucleotides that marks the beginning of protein synthesis in a messenger RNA (mRNA)
Start codon and its amino acid
AUG
Methionine
Define: Stop Codon
a sequence of three nucleotides in DNA or messenger RNA (mRNA) that signals the end of protein synthesis.
What are two alternate names for stop codons?
Termination Codon and Nonsense Codon
Stop Codons (3 total)
UGA
UAA
UAG
What enzyme transcribes the gene?
RNA Polymerase
Can RNA Polymerase work by itself? What else is required to initiate transcription of the gene?
No; it needs a positive transcription factor.
What is a cognate amino acid?
the specific amino acid that is paired with a particular tRNA molecule, meaning it is the exact amino acid that the tRNA is designed to carry and will be incorporated into a growing protein chain during translation
Define: Positive Transcription Factor
a protein that binds to specific DNA sequences near a gene, promoting the transcription of that gene, essentially “turning it on”
Define: Negative Transcription Factor
a protein that reduces or stops the transcription of a gene
Define: Affinity
the strength of the attraction between two biological molecules. It’s a measure of how likely and tightly the molecules will bind to each other.
Define: Mutation
a change in the DNA sequence of an organism (change of A,T,G and C in a molecule of DNA) that can go on to produce an alternate RNA or amino acid sequence
Role of the following in Translation: mRNA (Messenger RNA)
Contains Messages
It acts as the template carrying the genetic information from DNA to the ribosomes, where it is “read” to direct the sequence of amino acids during protein synthesis, dictating the structure of the resulting protein through its codon sequence
Role of the following in Translation: tRNA (Transfer RNA)
Transfers Amino Acids
Contains Anticodons that pair with mRNA Codons to put Amino Acids in the correct order
acts as an adaptor molecule, carrying a specific amino acid to the ribosome and matching it with its corresponding codon on the mRNA molecule, essentially “translating” the genetic code into a growing polypeptide chain
Role of the following in Translation: rRNA (Ribosomal RNA)
Facilitates matching of mRNA and tRNA;
Joins Amino Acids to synthesize a protein
the structural foundation of the ribosome, actively participating in the process of protein synthesis by facilitating the binding of messenger RNA (mRNA) and transfer RNA (tRNA) molecules, ultimately catalyzing the formation of peptide bonds between amino acids to build a polypeptide chain
What is the role of aminoacyl tRNA synthase?
Catalyzes the attachment of a given amino acid to the 3’ end of the cognate tRNA
When does initiation of translation occur?
When the small ribosomal subunit binds with the initiation factors and an initiator tRNA at the start codon of an mRNA, followed by the binding to the initiation complex of the large ribosomal subunit
What happens in the elongation stage of translation?
A charged tRNA binds to mRNA in the A site of the ribosome
A peptide bond is catalyzed between the two adjacent amino acids breaking the bond between the first amino acid and its tRNA
The ribosome moves on codon along the mRNA
The first tRNA is moved from the P site of the ribosome to the E site and leaves the ribosomal complex
What happens during the termination stage of translation?
Occurs when the ribosome encounters a stop codon
Release factors cause the polypeptide to be released and the ribosomal complex dissociates
What are the three types of point mutations?
Silent, Missense and Nonsense
Point Mutation
a change in a DNA sequence where only a single nucleotide base is altered
Silent Point Mutation
a change in a single nucleotide within a DNA sequence that does not result in a change to the amino acid sequence of the protein it codes for
Missense Point Mutation
a genetic change where a single nucleotide in DNA is altered, resulting in a different amino acid being coded for at that position in the resulting protein
Nonsense Point Mutation
a single nucleotide change in the DNA sequence results in a premature stop codon, causing the protein to be truncated and likely nonfunctional
Frameshift Mutation
a genetic mutation that occurs when a number of nucleotides are inserted or deleted from a DNA sequence that is not a multiple of three, causing the “reading frame” of the gene to shift, leading to drastically altered amino acid sequence in the resulting protein and usually rendering it nonfunctional
What is Gene Regulation?
the process used to control the timing, location and amount in which genes are expressed.
How is Protein Production affected by: Positive Transcription Factors?
directly increase protein production by enhancing the transcription of a gene
More mRNA is produced, which leads to a higher rate of protein synthesis on ribosomes; essentially, when a positive transcription factor binds to DNA, it promotes the process of copying the gene into mRNA, resulting in increased levels of the corresponding protein being produced in the cell
How is Protein Production affected by: Negative Transcription Factors?
directly inhibit protein production by binding to specific DNA sequences on a gene, preventing RNA polymerase from accessing the gene and thus blocking the transcription process, r
resulting in significantly reduced or completely halted production of the corresponding protein.
What do we mean when we say the code is redundant?
The code unnecessarily occurs over and over again.
Ribosome are composed of how many subunits? What are they called? What are they composed of?
Two
Large Subunit and Small Subunit
rRNA and Protein
A Site of a Ribosome
Aminoacyl
This site receives the new aminoacyl-tRNA, which carries the next amino acid to be added to the growing polypeptide chain.
P Site of a Ribosome
Peptidyl
This site holds the tRNA that currently carries the growing polypeptide chain.
E Site of a Ribosome
Exit
This site is where the deacylated tRNA (tRNA without an amino acid) is released from the ribosome after transferring its amino acid.
Prokaryote Vs Eukaryote Protein Synthesis – What is Similar?
Central dogma:
Both prokaryotes and eukaryotes follow the central dogma of molecular biology, where genetic information flows from DNA to RNA to protein.
Basic translation steps:
The process of translation, including initiation, elongation, and termination, occurs in both prokaryotes and eukaryotes using similar mechanisms.
Codon usage:
Both cell types use the same codon to amino acid code, meaning the same mRNA sequence will translate to the same protein sequence.
Ribosome function:
Although different in size, both prokaryotic and eukaryotic ribosomes function to read mRNA and facilitate the formation of peptide bonds between amino acids.
Prokaryote Vs Eukaryote Protein Synthesis – What is Different?
Transcription and translation coupling:
In prokaryotes, transcription and translation occur simultaneously in the cytoplasm, while in eukaryotes, transcription happens in the nucleus and translation occurs in the cytoplasm, separating the two processes.
RNA processing:
Eukaryotic mRNA undergoes extensive processing (splicing, capping, polyadenylation) before translation, which does not occur in prokaryotes.
Ribosome size:
Prokaryotes have smaller ribosomes (70S) compared to eukaryotes (80S).
The genetic code is degenerate. What does that mean?
Several mRNA codons code for the same amino acids
Can transcription and translation be coupled in prokaryotes?
Yes
Can transcription and translation be coupled in Eukaryotes?
No – transcription occurs in the nucleus and translation occurs in the cytoplasm
What are post-translational modifications?
changes that occur to proteins after they’ve been translated by ribosomes. These modifications can expand the range of functions of the protein
All of your cells contain the code to make all of your________?
proteins
What is the function of exonucleases in translation?
mRNA destroyers
enzymes that remove nucleotides from the ends of RNA strands, which can impact translation and gene expression.
How could a cell increase the amount of protein produced from a gene?
by enhancing the transcription of that gene into mRNA by
Promoter activity
Transcription factors
DNA methylation patterns
Post-transcriptional control:
mRNA stability:
Alternative splicing:
Translational control:
Ribosome binding site
Gene amplification:
Gene duplication
How could a cell keep a protein being made if it didn’t need to?
The primary way a cell controls protein production is by regulating which genes are “on” or “off” at a given time, meaning which genes are being transcribed into mRNA and which are not.
Other mechanisms to control protein levels:
mRNA degradation:
Once mRNA is produced, its stability can be regulated, meaning it can be quickly broken down if the cell doesn’t need the protein right away.
Translation regulation:
The process of translating mRNA into protein can also be controlled, allowing cells to fine-tune protein production even when a gene is transcribed.
Protein degradation:
Once a protein is made, it can be tagged and broken down by the cell’s machinery if it is no longer needed.
What are 3 causes of mutations?
- DNA Replication Error
- Mutagens (Radiation and Some Chemicals)
- Viral Infections
When do mutations not have major consequences?
When DNA is fixed by repair mechanisms and when the mutation occurs in body cells that do not replicate
What are four mechanisms that cells use during DNA Replication to avoid mutations?
- Base Pair Specificity
- DNA Polymerase Proof Reading
- Mismatch Repair
- Excision Repair
After repair mechanisms only 1 error in ______ million base pairs occurs
30
A mutation in the DNA always leads to a change in the amino acid sequence? True or False
False;
Examples Include
1.Silent Mutation
2.Mutation in regulatory region of the gene - how much protein gets made
3. Intron or part of the DNA that is not part of the gene
On average mutations ________ fitness. But there are exceptions.
Decrease
The point mutation that leads to sickle cell anemia is an example of 1) Silent 2) Missense 3) Nonsense?
Missense
Mutations can change _________ levels of protein structure.
All
Insertions and Deletions cause this kind of mutation?
Frameshift
Where would a frameshift mutation cause more change in a gene- at the beginning or the end?
Beginning
