7.2 & 7.3 Notes
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Transcription and translation are the two main processes by which genes are expressed into proteins. During transcription, DNA is copied into messenger RNA (mRNA) by RNA polymerase. In eukaryotes, mRNA undergoes processing after transcription where introns are removed and exons are joined together. Translation occurs where the mRNA is read by ribosomes to produce a polypeptide chain based on the mRNA sequence. There are three steps to translation - initiation, elongation, and termination. Gene expression is regulated at transcriptional and post-transcriptional levels through promoter regions, epigenetic modifications, and alternative splicing of mRNA.
7.2 & 7.3 Notes
- 1. IB Biology Chapter 2 Notes: Transcription & Translation AHL (7.2 & 7.3) NAME: Word Definition Polysome Many ribosomes translating the same mRNA at the same time Nucleoside triphosphates Nucleotides with three phosphates. They break off to provide energy for reactions Introns Portions of mRNA that are removed and not used for translation Exons Portions of mRNA that are used for translation Splicing The process of removing introns Promoter Portion of DNA in front of gene that RNA poly attaches to Release factor Protein that attaches to ribosome at stop codon Initiation Start of translation or transcription Elongation When the ribosome moves to read the next mRNA codon and add another amino acid to the growing polypeptide Termination The end of transcription or translation tRNA activating enzyme An enzyme that attaches the correct amino acid to a tRNA molecule A-Site The site on the ribosome where new tRNAs enter P-Site The middle site on the ribosome E-Site The site on the ribosome from which tRNAs leave after dropping off an amino acid
- 2. 7.2.7 Describe the promoter as an example of non-coding DNA with a function. 7.2.1 Gene expression is regulated by proteins that bind to specific base sequences in DNA. 7.2.2 The environment of a cell and of an organism has an impact on gene expression. 7.2.3 Nucleosomes help to regulate transcription in eukaryotes. 7.2.8 Analyze changes in DNA methylation patterns. 7.2.4 Transcription occurs in a 5’ to 3’ direction. 7.2.5 Eukaryotic cells modify mRNA after transcription. List functions of non-coding DNA sequences: What is a ‘Promoter?’ Enhancers: Silencers: Promoter-proximal elements: What is the role of the environment in gene expression? Example of Siamese cats: How do nucleosomes regulate transcription? What is the effect of direct methylation of DNA? Describe what steps occur in eukaryotes to modify pre-mRNA to mature mRNA before Translation:
- 3. 7.2.6 Splicing of mRNA increases the number of different proteins an organism can produce. 7.3.12 Use molecular visualization software to analyze the structure of eukaryotic ribosomes and a tRNA molecule. 7.3.11 tRNA-activating enzymes illustrate enzyme- substrate specificity and the role of phosphorylation. 7.3.1 Initiation of translation involves assembly of the components that carry out the process. How can ‘alternative splicing’ lead to greater variety in proteins produced in Translation? Ribosome tRNA Drawing of structure Description of structure Describe how tRNA-activating enzymes work: How do these enzymes illustrate enzyme-substrate specificity? Outline the steps ofInitiation:
- 4. 7.3.2 Synthesis of the polypeptide involves a repeated cycle of events. 7.3.3 Disassembly of the components follows termination of translation. 7.3.4 Free ribosomes synthesize proteins for use primarily within the cell. 7.3.5 Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes. 7.3.6 Translation can occur immediately after transcription in prokaryotes due to the absence of a nuclear membrane. 7.3.13 Identify polysomes in an electron micrograph. Outline the steps ofElongation: Outline the steps ofTermination: Explain why translation can occur immediately after transcription in prokaryotes,but not eukaryotes: What are polysomes?