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Bis 101
Lecture 9
| Question | Answer |
|---|---|
| What do structural gene code for? | Polypeptides |
| What do non-structural genes code for? | RNA's |
| What is the purpose of tRNA? | Tranlate mRNA into amino acids |
| What is the purpose of rRNA? | It is part of the ribosome |
| What is transcription? | The transcribing of DNA into an mRNA |
| What is the point of the promoter on the transcribed region? | The site for RNA polymerase to bind and begin transcription |
| What is the point of the regulatory sequence on the transcribed region? | The site for regulatory proteins to bind |
| What is the point of the terminator site on the transcribed region? | To end transcription |
| What are the three stages of transcription? | 1: Initiation 2: Elongation 3: Termination |
| In bacteria, what does the Initiation step of transcription do? | It is the recognition step where the sigma factor causes the RNA polymerase to recognize the promoter region on the DNA and bind to it |
| In bacteria, what does the Elongation step of transcription do? | The Sigma Factor detaches and the RNA polymerase synthesizes the mRNA for translation, and the DNA re-zips behind it |
| In bacteria, what does the Termination step of transcription do? | The RNA polymerase reaches the termination sequence so the RNA polymerase and newly made mRNA dissociate from the DNA |
| What is the similarities and differences between bacterial and eukaryotic transcription? | They are essentially the same, however, Eukaryotes have more proteins involved such as polymerase 1, 2, and 3. They also take an additional process with the mRNA. |
| What additional steps do Eukaryotes take with their mRNA? | They have a pre-mRNA phase that are processed so that the RNA can be spliced, which is where the exons are connected and the introns are removed. They also add the 3 tails and 5 caps. |
| What are snRNP's or "snurps"? | A splicesome that removes introns from pre-mRNA. Made of a small nuclear RNA and proteins. |
| What is the point of alternative splicing and how does it function? | A function so that a single gene can encode for more than one protein. Performed by splicesomes. |
| What is the 5 prime cap for? | Needed for exit of the mRNA from the nucleus and for binding to the ribosome |
| What is the 3 prime poly A tail and what is it for? | 100 to 200 adenine nucleotides attached to the 3 prime end. Increases the length and stability of the mRNA in the cytosol. |
| What is translation? | The process of making polypeptices from mRNA. Takes a lot of energy. |
| What are codons and how are they used? | Groups of three nucleotides that are read during translation to code for different amino acids |
| What is a degenerate in translation? | When more than one codon can signal for a single amino acid |
| What is an anticodon? | The 3 RNA nucleotides in the tRNA that are the opposites of the codons in the mRNA. These anticodons specify the amino acid. |
| What is aminoacyl-tRNA synthetase? | A substance that catalyzes the attachment of amino acids to tRNA |
| Do prokaryotes and eukaryotes have different kinds of ribosomes? | Yes. Prokaryotes have the 70S ribosome, while eukaryotes have the 80s. A much more complicated ribosome. Both are made of a large and small subunit though. |
| What is the purpose of the ribosome? | It is the site for polypeptide synthesis. It uses three different sites, termed A P and E. |
| What are the different uses of the APE sites in ribosomes? | The A site pairs the codon with anticodon and brings the associated amino acid on the tRNA. The P site collects the amino acids and forms them into a polypeptide. The E site is used to exit the ribosome. |
| What happens in the initiation stage of translation? | tRNA and ribosomal subunits assemble with the help of a ribosomal initiation factor, and also with the input of energy (GTP hydrolysis) |
| What happens in the elongation stage of translation? | Aminoacyl tRNA brings a new amino acid to the A site of the ribosome. A peptide bond is formed between the A site, the growing peptide chain, and the amino acid. The chain transfers to the A site and all the tRNA moves over one space until it exits. |
| What happens in the termination stage of translation? | The translation at the A site stops when a stop codon is found. The polypeptide is released. |
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24rory
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