Transcription and Translation I E T slideshow

Question 1

Transcription - Initiation

Answer 1

Initiation
Promoter region: a sequence of nucleotides in DNA that indicates where the RNA polymerase complex should bind to initiate transcription

-Key element of the promoter in eukaryotes is the TATA box (a portion of DNA with high percentage of Adenine and Thymine bases)

-Prokaryotes have a TATATT sequence instead for this

-RNA polymerase binds to a promoter region on the DNA same purpose

Question 2

Transcription - Elongation

Answer 2

Elongation
RNA polymerase complex works its way along DNA molecule

-Without needing a primer to be already in place

-Synthesizes mRNA strand that is complementary to template strand of DNA (T is replaced with U)

-RNA polymerases work in the 5ʼ → 3ʼ direction, using the 3ʼ→ 5ʼ DNA strand as a template strand.

As RNA polymerase moves along the DNA, it unwinds the DNA at the forward end of the enzyme

-RNA strand grows as nucleotides are added, one by one forming a temporary RNA-DNA double helix with the template strand

-As the RNA polymerase passes, the DNA double helix reforms

-Once an RNA polymerase molecule has started transcription and progressed past the beginning of a gene, another molecule of RNA polymerase may start producing another RNA molecule if there is room at the promote

Question 3

Transcription - Termination

Answer 3

The transcription is terminated when RNA polymerase recognizes a termination sequence.

Question 4

Translation - Initiation

Answer 4

-mRNA, tRNA and small ribosomal subunit bind with P site at start codon

-Only the first tRNA binds to P at start codon

-Large subunit binds using energy from GTP

Question 5

Translation - Elongation

Answer 5

mRNA read 3 nucleotides at a time in codons

-tRNA brings corresponding amino acid into the A site of the ribosome

-Ribosome catalyzes dehydration synthesis reaction between amino acids in P site and A site

-Peptide bond is formed

-Growing polypeptide now attached to tRNA in A site

-Ribosome moves forward one codon

-Free tRNA in P site exits out the back of ribosome on the E site

-tRNA (with polypeptide) moves into P site

Question 6

Translation - Termination

Answer 6

-Elongation continues until reaching a stop codon

-There is no amino acid for stop codon, just STOP

-Release factor binds and hydrolyzes the bond between the last tRNA and its amino acid

-New protein is free