the genetic code and trancription Flashcards
What is the central dogma of molecular genetics?
It is the concept that genetic information flows in one direction: DNA → RNA → Protein, involving replication, transcription, and translation.
What specifies an amino acid in the genetic code?
A triplet of nucleotides, known as a codon.
Which nucleotide bases are found in DNA?
Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
What is the initiator codon in the genetic code?
ATG, which codes for Methionine.
What are the three stop codons in the genetic code?
TAA (Ochre), TAG (Amber), and TGA (Umber).
What is a frame-shift mutation?
It is a mutation caused by the insertion or deletion of a nucleotide, altering the reading frame of the genetic sequence.
Why is the genetic code considered universal?
It is shared across viruses, bacteria, fungi, plants, and animals, with few exceptions in mitochondria and some unicellular eukaryotes.
What are the three classes of RNA polymerase in eukaryotes, and what do they transcribe?
RNA Polymerase I: Ribosomal RNA (rRNA).
RNA Polymerase II: Messenger RNA (mRNA).
RNA Polymerase III: Transfer RNA (tRNA) and one small rRNA.
What are the steps of transcription in eukaryotes?
Initiation: RNA polymerase binds to the promoter with transcription factors.
Elongation: RNA polymerase synthesizes RNA in the 5’ → 3’ direction.
Termination: RNA is cleaved, and a poly(A) tail is added.
How does transcription differ between prokaryotes and eukaryotes?
Prokaryotes: Transcription and translation occur in the cytosol simultaneously.
Eukaryotes: Transcription occurs in the nucleus, followed by RNA processing and translation in the cytosol.
What is the role of promoters in transcription?
Promoters are DNA sequences where RNA polymerase binds to initiate transcription.
What is the lac operon, and where is it found?
The lac operon is a gene regulatory system in E. coli that controls the expression of enzymes involved in lactose metabolism.
What happens during rho-independent termination in prokaryotes?
Transcription stops when RNA forms a hairpin loop followed by a poly(U) sequence.
What is the most important point of control in gene expression?
What is the most important point of control in gene expression?
