4_Transcription_Translation_Flashcards
What is the central dogma of molecular biology?
DNA → RNA → Protein.
What are the two main processes involved in the central dogma?
Transcription (DNA to RNA) and Translation (RNA to Protein).
Why are proteins essential for life?
They fight disease, build tissues, act as enzymes, and serve as signals.
What determines a protein’s structure and function?
The unique sequence of its 20 possible amino acids.
What is transcription?
The process of synthesizing mRNA from a DNA template.
Where does transcription occur in eukaryotes?
In the nucleus.
What percentage of the human genome is transcribed into mRNA?
Less than 2%.
What carries the genetic code from the nucleus to the cytoplasm?
Messenger RNA (mRNA).
What is the role of RNA polymerase?
To transcribe DNA into mRNA.
What are transcription factors?
Proteins that regulate the initiation of transcription.
What is the function of a promoter region?
It binds RNA polymerase to initiate transcription.
What are introns and exons?
Introns are non-coding regions, and exons are coding sequences.
What happens during initiation?
RNA polymerase binds to the promoter, and DNA unwinds.
What happens during elongation?
RNA polymerase synthesizes mRNA in the 5’ to 3’ direction.
What signals the end of transcription?
A termination signal in the DNA.
What is added to the 5’ end of mRNA?
A 7-methylguanosine cap.
What is added to the 3’ end of mRNA?
A poly(A) tail.
What is splicing?
The removal of introns and joining of exons in pre-mRNA.
What is alternative splicing?
Producing multiple protein variants from one gene.
What is translation?
The process of converting mRNA into a protein.
Where does translation occur?
In the ribosome.
What are the three main steps of translation?
Initiation, elongation, and termination.
What is the role of tRNA in translation?
It carries amino acids to the ribosome.
What is a codon?
A three-nucleotide sequence that codes for an amino acid.
How many codons specify amino acids?
61 codons.
What are the stop codons?
UAA, UAG, UGA.
Is the genetic code universal?
Yes, nearly all organisms use the same code.
What happens during initiation?
The small ribosomal subunit binds to mRNA, and the first tRNA pairs with the start codon.
What happens during elongation?
Amino acids are added one by one, forming a polypeptide chain.
What happens during termination?
A stop codon signals the release of the polypeptide.
What modifications occur after translation?
Folding, chemical group additions, and cleavage into smaller peptides.
Why are post-translational modifications important?
They ensure the protein’s proper function and activity.
Where does transcription occur in prokaryotes?
In the cytoplasm.
Where does transcription occur in eukaryotes?
In the nucleus.
Do prokaryotes modify their mRNA after transcription?
No, the primary transcript is the mature mRNA.
What type of mRNA do prokaryotes produce?
Polycistronic mRNA (one mRNA can encode multiple proteins).
What is an ORF?
A sequence of DNA with a start codon, stop codon, and potential to code for a protein.
Why are ORFs important?
They help identify coding regions in DNA.
What is the central enzyme in transcription?
RNA polymerase.
What molecule brings amino acids to the ribosome?
Transfer RNA (tRNA).
What is the first amino acid in protein synthesis?
Methionine (coded by AUG).
How is mRNA stabilized in eukaryotes?
By a 5’ cap and poly(A) tail.
What are ribosomes made of?
rRNA and proteins.
Where are ribosomes found?
In the cytoplasm and on the rough ER.
What are the ribosome’s functional sites?
A-site (aminoacyl), P-site (peptidyl), and E-site (exit).
How does tRNA ensure accuracy in translation?
By matching its anticodon to the mRNA codon.
What is the role of enhancers and silencers?
To regulate transcription by increasing or decreasing gene expression.
What is polyadenylation?
The addition of a poly(A) tail to mRNA’s 3’ end for stability.
What are transcription factors?
Proteins that control the rate of gene transcription.
What is the function of ribosomal RNA (rRNA)?
It forms the core of the ribosome’s structure and catalyzes protein synthesis.
