Topic 15 - Ribosomes and Protein Synthesis Flashcards
Gene
Region of DNA that contains a code that specify proteins through RNA
Central Dogma of Gene Expression
Genes specify the sequence of mRNAs, which in turn specify the sequence of proteins
Codon
Three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation
Anticodon
Three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon
What does “the genetic code is redundant but specific” mean?
- Redundant: more than one codon corresponds with each amino acid
- Specific: a codon specifies only one amino acid
What are the 3 kinds of RNA involved in protein synthesis? Describe what each does.
- mRNA (messenger RNA)
- carries the coding sequences for protein synthesis (transcripts) - tRNA (transfer RNA)
- carries amino acids to the ribosomes during protein synthesis; does translation - rRNA (ribosomal RNA)
- forms the core of a cell’s ribosomes (the structures in which protein synthesis takes place)
Where does transcription take place?
Nucleus
What is the final product of transcription?
mRNA strand
What enzyme adds RNA nucleotides to create mRNA?
RNA polymerase
Which RNA nucleotides are complementary to the DNA nucleotides adenine, thymine, guanine, and cytosine?
Uracil, adenine, cytosine, and guanine
What do transcription factors do? What are they made of? What is the transcription initiation complex?
Transcription factors are proteins involved in the process of converting, or transcribing, DNA into RNA. Transcription factors include a wide number of proteins, excluding RNA polymerase, that initiate and regulate the transcription of genes.
Which strand is transcribed to make mRNA - the coding strand or the template strand?
Template strand
What happens during eukaryotic pre-mRNA processing?
- When an RNA transcript is first made in a eukaryotic cell, it is consider a pre-mRNA and must be processed into mRNA
- A 5’ cap is added to the beginning of the RNA transcript and a 3’ poly-A tail is added to the end
- Introns (“junk” sequences) are removed and exons are put back together by spliceosomes
Where does transcription take place?
Ribosomes
What is the final product of translation?
Polypeptide chain (protein)
What happens on the small and large ribosomal subunits?
The small subunit decodes the genetic message and the large subunit catalyzes peptide bond formation.
- mRNA is “fed” through the ribosome; tRNA goes through the A, P, and E sites in the large subunit
Where are codons found?
mRNA
Where are anticodons found?
tRNA
What is the relationship between a codon and an anticodon?
Codons in the mRNA bind to the anticodons in the tRNA during protein synthesis (translation)
Aminoacyl-tRNA synthetase
Enzyme that attaches the appropriate amino acid onto its corresponding tRNA (first step of translation)
Initiation
Ribosome assembles around the target mRNA (forming an initiation complex) and the start codon 5’ AUG is recognized
Elongation
The tRNA transfers an amino acid to the tRNA bound to the next codon, forming a peptide bond between the two amino acids. The ribosome then shifts to the next codon to continue the process, creating a polypeptide chain.
- tRNA moves through the A, P, and E sites of the ribosome respectively.
Termination
Elongation continues until a “stop” codon enters the A site on the ribosome, terminating the process.
Point mutation
Occurs when a single base-pair is added, deleted or changed
