1883820
Description
Flashcards by itstinachen, updated more than 1 year ago
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Created by itstinachen
almost 10 years ago
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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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