Chapter 7 Flashcards
(20 cards)
What is the Central Dogma of Molecular Genetics?
DNA is TRANSCRIBED into complementary messenger RNA, and ribosomes TRANSLATE messenger RNA into a specific sequence of amino acids
This process is fundamental to gene expression and protein synthesis.
What are the three sequential processes of transcription?
Initiation, Elongation, Termination
These processes occur in the nucleus and are essential for RNA synthesis.
What occurs during the initiation phase of transcription?
RNA polymerase binds to the DNA and unwinds near the beginning of a gene
The promoter sequence allows for the binding of RNA polymerase.
What is a promoter?
The nucleotide sequence that lies just upstream from the start of a gene
It facilitates the binding of RNA polymerase.
What is the TATA box?
A section of the promoter with a high percentage of adenine and thymine bases
It requires less energy to open the DNA helix due to only having 2 hydrogen bonds between A & T.
What is the direction of RNA synthesis during elongation?
RNA is made in the 5’ to 3’ direction
The template strand of DNA runs in the 3’ to 5’ direction.
What happens during the termination phase of transcription?
Transcription is terminated when RNA polymerase recognizes a termination sequence
The RNA transcript is released, allowing RNA polymerase to bind to another promoter.
What are post-transcriptional modifications?
Capping, Tailing, and Splicing
These modifications enhance RNA stability and prepare it for translation.
What is the function of the Poly-A tail?
Protects mRNA from degradation and aids in translation efficiency
It consists of 50-250 adenine nucleotides added to the 3’ end.
What is the role of the 5’ cap?
It serves as the initial attachment site for ribosomes
The cap is made up of 7 methylated guanines.
Define exons and introns.
Exons: coding sequences; Introns: non-coding sequences
Introns must be removed from mRNA to ensure correct protein synthesis.
What is the role of the spliceosome?
Removes introns from mRNA and joins exons together
It is a complex of proteins and RNA that facilitates splicing.
What is alternative splicing?
Produces different mRNAs from pre-mRNA, allowing multiple polypeptides from a single gene
This increases protein diversity.
What are codons?
Triplets of RNA bases that are translated into amino acids
61 codons specify 20 different amino acids.
What is the wobble hypothesis?
The third base in a codon can change without altering the amino acid specified
This redundancy minimizes errors that could lead to mutations.
What are start codons?
Initiator codon AUG, which codes for methionine
It signals the start of translation.
What are stop codons?
UAA, UAG, UGA, which signal the end of a polypeptide chain
These codons cause the ribosome to terminate translation.
What is the lac operon?
A cluster of genes that regulates protein needed for lactose metabolism
It is an inducible operon activated by lactose.
What is the trp operon?
Regulates the production of tryptophan in prokaryotic cells
It is an example of enzyme repression.
What are the types of mutations?
Substitution, Insertion, Deletion, Inversion, Silent, Nonsense, Missense, Frameshift
Each type can have different effects on protein function.
