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Transcrip/Transla
Bio 2 Lecture 14
| Question | Answer |
|---|---|
| When does gene expression occur? | Occurs when information, stored in DNA as genes, is converted into instructions (mRNA) for making proteins. |
| How to express the genetic information? like what is used and how | The mRNA is used as the template for synthesize of a protein. The ribosomes (rRNA) organize and bind the specific sequence of amino acids as mapped by the mRNA. |
| Explain the transcription process in prokaryotic genes. | RNA polymerase move information from DNA to mRNA, converting the language of DNA |
| Explain the translation process in prokaryotic genes. | Uses the mRNA codon reading frames to get the correct sequence of amino acids and with the help of tRNA and rRNA, it forms a single polypeptide. |
| Give an overview of the transcription process | The double stranded DNA separates into single stranded DNA. RNA polymerase binds, forming a transcription bubble. The template strand (3' to 5') is read to make mRNA. The strands separate |
| Which direction is the template strand? | 3' to 5' |
| Which direction is the coding strand? | 5' to 3' |
| What direction does mRNA grows? | mRNA grows 5' to 3' |
| What direction does RNA polymerase moves DNA? What does it make? | RNA polymerase moves to DNA 5' end which makes mRNA strand (See slide 7) |
| What is transcription? | The process of making RNA from DNA template |
| What are the components of transcription? | 1)Promoter sequence=RNA polymerase binding 2)Start site (where transcription begins) 3)Termination sequence (signals the end) |
| What are the 3 stages of transcription? | 1)Initiation 2)Elongation 3)Termination |
| What happens in initiation? | RNA polymerase binds to the promoter region and tells the polymerase where to park and open up DNA to form transcription bubble |
| What happens in elongation? | Stage where RNA strand gets longer bc of the addition of new nucleotides. |
| In what direction does RNA polymerase moves in the template strand? | RNA polymerase moves along the template strand, in the 3' to 5' direction. |
| What happens in termination? | Rich area in C and G nucleotides and they bind together, which causes the polymerase to stall |
| What is UAA? | It's not a code for an amino acid, it places a stop factor in the reading frame which ends translation |
| What are codons? | It's where the instructions for building a polypeptide come (in the form of 3 nucleotides) |
| What's the start codon? | AUG aka Met |
| How many codons for amino acids and what are they called? | 61 different codons known as genetic code |
| What are the 3 types of RNA that translation require? Explain what they are | 1) tRNA: transfer RNA transports amino acids to mRNA 2)rRNA: ribosomal RNA is site where polypeptide is assembled 3) mRNA: messenger RNA carries the codon sequence info from DNA to make protein |
| What are the stages of translation? | 1) Initiation 2) Elongation 3) Termination |
| What happens in initiation? | A complex is formed. 1) On a small subunit, mRNA binds, lining up the start codon in the P-site 2) d-met tRNA binds to AUG in P-site, then the small and large rRNA subunits come together |
| What happens in elongation? | Adds amino acids by bringing them to empty A site on rRNA. |
| Elongation continues until what? | Until the ribosome encounters a stop codon |
| What happens in termination? | 1) Stop codons are recognized by release factors which release the polypeptide from the ribosome 2) Release factors (protein) bind to the A-site causing the release of the polypeptide from the ribosomal RNA. 3) The initiation complex dissociates |
| What is special about transcription and translation for prokaryotes? | It occurs at the same time |
| What's the sequence of gene flow recognition sequences? | TAC (in template strand, aka DNA), then AUG (in transcription, aka RNA) and finally Met (in translation, aka a protein) |
| Does RNA polymerase have proof-reading abilities? | No |
| What does translation allow? | Allows less stringent pairing between the codon and the anticodon aka mistakes can occur without consequences |
| Can severak codons code the same amino acid? | yes, so that errors can happen without changing the protein |
| So what does wobble pairing help? | Helps avoid translation errors |
| What position can change without affecting the amino acid? | The 3rd sequence |
| What's the difference between eukaryotic and prokaryotic gene flow? | PROKARYOTES: No nucleus, DNA in cytoplasm, transcription and translation in cytoplasm, mRNA not processed, one RNA polymerase EUKARYOTES: Nucleus, DNA in nucleus, transcription in nucleus and translation in cytoplasm, RNA processed, manu RNA polymerase |
| Explain eukaryotic gene expression | Remember that transcription happens in the nucleus and translation in the cytoplasm. It goes from DNA to RNA to mRNA, AA chains and finally protein. See slide 34 |
| So what are the major differences in eukaryotic gene expression? | 1) Pre-mRNA is made in the nucleus, and has a non-coding DNA called introns which must be removed 2) RNA polymerase II reaches the poly-A tail region and falls off (no G-C hairpin) |
| Know the structure of a pre-mRNA | See slide 36. Introns are non-coding regions and exons are sequences that will be translated |
| What does pre-mRNA must undergo before translation? | A maturing process to remove introns and slice together exons |
| What is a splicesome? | Enzymes that function together, snips out the introns and glues together the exons (so named because they EXIT the nucleus). Introns degrade in the nucleus. |
| What gives mature mRNA? | The 5' CAP and the poly-A tail are added to pre-mRNA to give mature mRNA |
| What is alternative splicing? | Fewer genes are needed to make proteins |
| What are the 3 categories of mutations? Explain them | 1) Benefical mutations (Increase the fitness of the organism) 2) Neutral mutations (Do not affect organism) 3) Deleterious mutations (Decrease fitness of organism) |
| What is a mutagen? | A chemical or physical agent that interacts with DNA and causes a mutation. |
| What's the starting point for evolution? | Mutations bc it allows new genetic material |
Created by:
Malayka
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