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Chp. 1314
gene regulation and mutation
| Question | Answer |
|---|---|
| Turned On Gene | gene is being transcribed and translated. protein codes are EXPRESSED. |
| Turned off genes | it is not being transcribed and no proteins are produced. important to produce right amount of protein |
| Eukaryotic cells differentiate | they become specialized for a particular function |
| Active genes | each cell has a different set of active genes |
| DNA packing | DNA must be tightly coiled in order to fit into the nucleus. |
| Histones | are small proteins that attach to the dna, histones also loosen and allow dna to uncoil during transcribed. |
| Nucleosome | is a region of DNA that is wrapped around * histone proteins. Nucleosomes are wrapped into a helix then is supercoiled. |
| Female Mammals | , one X chromosome is inactivated - very tightly coiled and compacted, so the genes on this chromosome are not expressed. she is hetrozygous. *calico cat |
| Transcription Factors | are proteins that turn transcription of a gene off and on. |
| Activators | *type of transcription factor. The activator binds to an enhancer sequence in the DNA. This allows the RNA polymerase to bind to the promoter and begin transcription. The gene is active, it is expressed, and its protein product is made. |
| Repressors | bind to silencer sequences in the DNA and prevent transcription from taking place. |
| genome | all DNA |
| proteome | all protein |
| Introns | Must be spliced out before it can be translated |
| so different mRNA molecules can be produced from the same transcript | These mRNAs will have different base sequences, so they will be translated into different proteins |
| mRNA breakdown | mRNA doesnt survive long in cytoplasm. The longer it survives the more it can be translated so proteins are made of it. |
| Inhibition of translation | An mRNA molecule may be transcribed, but it may not be translated immediately or at all. Inhibitory proteins may prevent translation |
| Protein Activation | After a protein is translated, it still may not be functional. Some proteins need to be cleaved into a shorter molecule or modified |
| Protein Breakdwon | The lifespan of a protein is controlled by the cell. some proteins survive for long periods of time. others are rapidly broken. |
| Gene expression | can also be regulated by events outside the cell. |
| Signal transduction pathways | convert messages received at the cell membrane into responses within the cell |
| mutation | is any change in the nucleotide sequence of DNA. even changing a single base can have a huge impact on the final protein. |
| Base Substitution | The replacement of one nucleotide with another. Changing a codon from G A A to G U A changes the amino acid in the protein from glutamate to valine |
| Silent Mutations | have no effect. For example, changing a codon from G A A to G A G would not change the protein, because they both code for the same amino acid. |
| Changing a codon to a stop codon | prematurely terminates translation. Only part of the protein is made. |
| Inseriton or deletion of a nucleotide | changes the reading frame of the message. This usually changes the amino acid sequence of the protein |
| Mutagens | are agents that cause mutations. Chemical agents like nitrous acid and physical agents like UV light and X rays |
| Repair of DNA | Reactive chemicals in the environment, radiation, X rays and UV rays can cause changes in the DNA that can be very harmful to the cell. However, cells have mechanisms for repairing damage to DNA |
| nucleotide excision repair | in which the incorrect nucleotides are removed, and the resulting gap is filled with the correct nucleotides. |
| disorder xeroderma pigmentosum | individuals are hypersensitive to light and mutations in their skin cells caused by UV light are left uncorrected and cause skin cancer |
| Cancer | is a result of mutation that alter gene expression |
| Oncogene | is a gene that cause a to become cancerous |
| proto-oncogenes | normal genes, if they are mutated, they can become oncogenes. found in somatic cells. |
| Virus | insert an oncogene into host cell's DNA |
| growth factors | proteins that stimulate cell division |
| BRCA 1 and 2 | dna repair genes |
| 3 ways to convert proto-oncogenes to oncogenes | translocation of gene mutation with the gene multiple copies of the gene |
| Translocation | gene is moved to another location, gets new promoter, causes it to transcribe and translate more often to produce excess protein. *leukemias and lymphomas |
| Mutation within the gene | if the proto-oncogene codes for a protein that stimulates cell division, a mutation may cause it to produce a supercharged version of the protein, |
| Multiple copies of the gene | If all the copies of the gene are transcribed and translated, more of the stimulatory protein will be produced. *squamous cell carcinomas(skin cancer) |
| Tumor suppressor genes | proto-oncogenes, inhibit cell division. when its mutated then inhibition is removed and cell is more likely to divide. |
| Ras | oncogene that overstimulates cell division. form tumors. |
| p53 | tumor suppressor gene that inhibits cell division. |
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