Gene Expression PDF

# Gene Expression Gene expression is the process of a gene making a protein to produce something functional. - Not every gene is expressed - Gene expression has to be regulated - Certain body parts don't need certain genes codes present in that area, so the gene is not expressed ## Gene Expressi...

# Gene Expression Gene expression is the process of a gene making a protein to produce something functional. - Not every gene is expressed - Gene expression has to be regulated - Certain body parts don't need certain genes codes present in that area, so the gene is not expressed ## Gene Expression in Prokaryotes vs. Eukaryotes ### Prokaryotic - Only DNA inside, no nucleus - Transcription and translation just happen - Control of gene expression affects transcription/translation ### Eukaryotic - No traveling of DNA outside of the nucleus - More opportunities for gene regulation ## Gene Expression Involves Transcription - When an RNA polymerase makes mRNA from DNA template ## Transcription Factors: Regulatory Proteins that affect transcription and translation - Found in both eukaryotes and prokaryotic cells ### Areas where proteins attach - **Promoter**: Helps the RNA start transcriptions. Other attach to stop it. - **Enhancer**: Increases transcription ## Environmental Factors that Affect Gene Expression - UV light - Lack of nutrients - Too much - **Repressors**: Block the DNA polymerase from performing transcription ## Lac operon - Attaches to the 'Operator' so RNA polymerase cannot work and protein won't be produced - When the gene doesn't need to be expressed, it's okay ## Certain genes need to be expressed: Example of Gene Expression - **Lactose**: Bacteria want to break down the sugar lactose by lactose enzyme ### Repressor - The repressor has to be removed so the polymerase can undergo transcription. - Then mRNA is used to produce protein. - The gene is expressed that contains the enzyme able to break down lactose ### Diagram of Gene Expression - No lactose: Repressors can block the enzyme from being created. No gene expression. - Lactose: Repressors can't block the enzyme from being created. Gene expression. ## Gene Regulation in Eukaryotes ### Transcription - Gene that is made of DNA is "rewritten" to mRNA. - DNA polymerase makes a copy of the DNA sequence called mRNA. - mRNA carries the genes' protein information encoded in DNA. ### Post Transcription - mRNA is made in transcription before translation - Examination of mRNA strand is done. - Certain areas of RNA are removed. ### RNA Splicing - The process of removing introns (gene is cut) - **Introns**: removed RNA regions. - **Exons**: regions of mRNA that remain. - Exons are connected together through splicing - RNA splicing can affect remaining exons ## Translation - **eIF-2** helps translation happen - Making a polypeptide chain of amino acids - These are then made into protein ### Stages - **Initiation**: mRNA + ribosomes come together to make the first tRNA - **Elongation**: Amino acids are brought to ribosome by tRNA. - **Termination**: Polypeptide chains are released. ### Post-Translation - Chemicals can be added or removed to proteins. - Change where/how they function, impacting expression ## Why Gene Expression is Important - Impacts: * Height * Eye color * Blood type * Hair color - Also important when cells in the body aren't functioning correctly. ### Example: Cancer - Can have expression or none expression of certain genes - Can hurt situations - Mutation that increase translation of genes that speed up cell division increases production of cancer cells dividing. ## Genetic Code: the relationship between nucleic acid sequences and amino acid sequences - **First Letter of Codon**: U, C, A, G - **Second Letter of Codon**: U, C, A, G - **Third Letter of Codon**: U, C, A, G - Each row represents a different amino acid. - **Stop** codons stop the process of translation. - **Start** codon begins the process of translation.