DNA transcription/translation Flashcards
What is transcription catalyzed by?
RNA polymerase
Where does transcription occur?
mostly in the nucleus
What are the 3 types of RNA?
messenger, transfer, ribosomal
What does messenger RNA do?
template for translation (PROTEIN SYNTHESIS)
What does transfer rNA do?
reads genetic code in mRNA and transfers appropriate amino acid to a growing polypeptide chain during translation
What does ribosomal RNA do?
component of ribosome (cell machinery for translation)
What direction does transcription happen?
• read 5’ to 3’ direction (like DNA polymerase)
T/F: RNA poly requires a primer
• RNA polymerases do NOT require a primer (unlike DNA polymerase)
False
Adenine binds with ____ in RNA
• Uracil binds with adenine (instead of Thymine in DNA)
Transcription Begins at a ______
• Begins at a promoter
Name 2 inhibitors of transcription
• Actinomycin D, • Rifampin:
What does actinomycin D do?
inserts into double helical DNA and prevents movement of polymerase along template DNA; inhibits both prokaryotic and eukaryotic; used for chemo
What does rifampin do?
inhibits prokaryotic transcription by binding to prokaryotic RNA polymerase; used to treat TB
What do most eukaryotic DNA’s have on the 5’ end? 3’ end?
5’–>cap, 3’–>poly A tail
What does the 5” cap do?
protects mRNA from degradation by ribonucleases
What does the poly A tail do?
enhances translation process
sequences removed by splicing are
introns
sequences retained after splicing
exons
• Addition of 5’ cap, splicing, and poly(A) tail occur in the ____
nucleus
What does reverse transcriptase do?
produces DNA from RNA
cDNA synthesis commonly used to ____
clone cellular genes
Codons are
a set of 3 nucleotides
• Set of 3 nucleotides codes for a ____
amino acid
What is the start codon?
AUG (school starts in AUGust)
What are the stop codons?
UAA, UAG, UGA
codons read by tRNAs using _____, which are complementary to codons
anticodons
What does it mean for the genetic code to be degenerate? how is this helpful?
the same amino acid can be encoded by more than 1 codon. minimizes deleterious effects of mutations!!!
codes for the SAME amino acid: ____
silent mutation
codes for a DIFFERENT amino acid: _____
missense mutation
codes for a STOP codon and results in premature termination: _____
nonsense mutation
nucleotide insertion or deletion changes the reading frame: _____
frameshift mutation
T/F: Genetic code is universal
True
Where does translation occur?
• Occurs on RIBOSOMES, consists of proteins and rRNAs
• Starts from ___ encoding methionine and terminates at ___ codon
AUG, stop
What inhibits translation?
antibiotics, toxins
Prokaryotic ribosome consist of which subunits?
• Prokaryotic: 30s + 50s = 70s
Eukaryotic ribosome consist of which subunits?
• Eukaryotic: 40s + 60s = 80s
Where are ribosomes synthesized in eukaryotes?
i. Ribosomes synthesized in nucleolus and transported to cytoplasm
Where does translation occur?
• Ribosomes and mRNAs meet in cytoplasm and this is where translation occurs!
• __________ attach correct amino acids to their tRNAs
• Aminoacyl tRNA synthetases attach correct amino acids to their tRNAs
T/F: ii. Each synthetase is specific to one amino acid and its corresponding tRNAs
True
T/F: • Multiple ribosomes can bind a single mRNA at different points and perform translation
True
What is a polysome?
• Polysome: complex of mRNA and multiple ribosomes (allows efficient use for protein synthesis)
What are the antibiotics that inhibit prokaryotic ribosome?
- Streptomycin
- Tetracycline
- Chloramphenicol
- Erythromycin
What does diphtheria toxin do?
inhibits eukaryotic protein synthesis by inactivating translation factor (eEF2); toxin gene encoded by LYSOGENIC bacteriophage
