Protein Synthesis: Transcription and Translation

Flashcards by itstinachen, updated more than 1 year ago
Created by itstinachen about 6 years ago


grade 12 bio tdsb version sources - nelson 12 textbook

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Question Answer
What are the 3 stages of transcription? Initiation Elongation Termination
Describe the initiation process of DNA transcription. Promoter regions (TATA box) is detected by transcription factors. Following, RNA polymerase binds to and separate the DNA strands.
Describe the elongation process of DNA transcription. Once RNA polymerase opens the double helix, ONE mRNA strand begins to synthesize accordingly. **the mRNA begins to transcribe at the start sequence/codon ONLY. One DNA strand acts as the template strand, to transcribe the mRNA strand, while the other becomes the coding strand.
True or false: The promoter region is upstream from the initiation site and gets transcribed. False, the promoter region does NOT get transcribed
Describe the termination process of DNA transcription. When RNA polymerase reaches a termination sequence on the template strand (complementary to), trancription stops. (UGA, UAA, UAG --> ACT, ATT, ATC)
A complementary RNA strand is synthesized in the direction of? 5'-3'/3'5'?  5'-3'
Describe what modifications the mRNA strand undergoes before leaving the nucleus, to serve what purpose? 1. 5' cap (guanine nucleoside trphosphate, short GTP) is added to the start of primary transcript. This protects the mRNA from digestion. 2. A "poly A tail" (50-250 adenine nucleotides) is added to the 3' end of the RNA. Also prevents degradation of mRNA 3. Splicing: INTRONS are nonfunctional segments of nucleotides that are snipped out of the chain. EXONS code for functional polypeptides and are rejoined by ligase
Describe the structure of tRNA. - clover-leaf shape - single stranded molecule with attachment site at one end of an amino acid, and the opposite end contains an anticodon (3 nucleotide bases complementary to mRNA codon)
If the mRNA codon is UUU, how will the corresponding tRNA look like? - 3' end holds amino acid (phe) according to chart - anticodon has the code AAA
Which enzyme joins the amino acid to tRNA? aminoacyl-tRNA synthetase
Explain the different sites on a ribosome unit. Ribosomes are made of large and small subunits that clamp on to the mRNA strand. P site (P for polypeptide) - holds tRNA carrying the growing pp chain A site (A for amino acid) - holds tRNA carrying the next aa to be added to the pp chain E site (E for exit) - discharges tRNA from ribosome
Describe translation process - start codon AUG attaches to the small ribosomal subunit, large and small subunit clamps onto strand - ribosome moves along mRNA, reading codons - translation only begins at AUG (start) codon, which corresponds to the a. acid met - the process of elongation continues until a stop codon is read in the A site. - release factors recognizes that the ribosome has stalled and causes the ribosome subunits to disassemble
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