Chapter 17 Flashcards
Translation
Sequence of mRNA bases are converted to an amino acid sequence
Codons
Groups of three RNA nucleotides that the instructions for building a polypeptide
How many codons are there?
61 to specify amino acids and three codons as start and stop signals
Start codon
AUG codon that signals the start of protein construction
Stop codons
UAA, UAG, and UGA that tell the cell when a polypeptide is complete
Genetic code
Collection of codon-amino acid relationships
Two types of molecules with key roles in translation
tRNAs and ribosomes
tRNA
Molecular bridges that connect mRNA codons to the amino acids they encode
Anticodon
Sequence of three codons at the end of each tRNA that binds to specific mRNA codons
Template strand
strand read by RNA polymerase in transcription
coding strand
strand of DNA that is not transcribed during synthesis of RNA
Transcription in Eukaryotic differences
- Three RNA polymerase: RNA polymerase 1, 2 and 3
- Larger, more diverse promoters, including TATA box
- General transcription factors recognize promoters rather than sigma proteins.
- At termination a poly(A) signal is transcribed rather than a hair pin
- Transcription occurs in the nucleus and translation occurs in the cytoplasm.
TATA box
short DNA sequence in many eukaryotic located about 30 pairs upward of the transcription start site. Important for assembling general transcription factors and RNA polymerase at the core enzyme.
General transcription factors
Group of proteins that assemble on promoters and help RNA polymerase initiate transcription
Termination of transcription for eukaryotic protein-coding genes
A DNA sequence near the end of each gene called poly(A) signal, is transcribed.
The RNA downstream of the poly(A) signal sequence is cut by an enzyme as the polymerase continues to transcribe the DNA template.