AP Biology Review Packet 4: Viruses, Bacteria and Expression & DNA Technology 3A1- DNA, and in some cases RNA, is the primary source of heritable information. 3B1- Gene Regulation results in differential gene expression, leading to cell specialization. 3C3- Viral Replication results in genetic variation, and viral infection can introduce genetic variation into the hosts. 2C1- Organisms use feedback mechanisms to maintain internal environments and respond to external environmental changes. 1. Chromosome structure a.Nucleosome- packing unit of DNA wrapped around a histone b.Nucleosomes coil together to make fiber; loops coil; further compacted into chromosomes c.Euchromatin is loosely coiled DNA (can be read for mRNA so it is turned on) d.Heterochromatin is tightly coiled DNA (cannot be read for mRNA so it is turned off) e.Histone acetylation refers to chemical that causes DNA to become less packed (turned on) f.Satellite DNA (Tandemly Repetitive DNA)- Repeated DNA sequences that are present in hundreds or thousands of copies (usually 5-10 nucleotides) g.Interspersed Repetitive DNA- Repeats not adjacent- scattered throughout the genome. h.Telomeres are repeated sequences (usually TTAGGG) at tips of chromosomes. Used to conserve chromosomes because of lagging strand problems. 2. Regulation of Transcription/Translation a.Enhancers- Areas on genome that are non-coding that are located at a distance from a promoter. Transcription factors can bind to these areas and cause transcription of certain genes. (turns on) b.MRNA Degradation- mRNA has a life span in the cytoplasm (can last a few hours to a week). (turns off) c.RNA processing (intron splicing, poly a tail, gtp cap) (turn on and alter expression) d.Histone Acetylation (turn on) e.Methylation- marks on outside that turn DNA on or off (epigenetics) f.Translation Repressors (turn off) g.Posttranslational modifications- folding, cleaving, etc. (alter expression) h.Transposons- jumping genes can enhance or reduce transcription translation by where they land 3.Viruses (not alive) a.Can be DNA or RNA (injected into host and takes over host energy/enzymes to make more of itself) b.Protein coat called capsid c.Retroviruses have reverse transcriptase; which is used in recombinant DNA tech- ex. AIDS d.Can allow for new gene combination in host by transduction (taking a piece of DNA with them when they break out) e.Lytic cycle (virulent/active) and Lysogenic cycle (dormant/temperate) 4. Regulation of Gene Expression in Bacteria as Model a.Bacteria are prokaryotic with a single circular chromosome b.Bacteria express all the genes needed for a product (more than one gene at a time) c.
- Маловероятно. Помимо всего прочего, в списке очередности указано, что это посторонний файл. Надо звонить Стратмору. - Домой? - ужаснулся Бринкерхофф. - Вечером в субботу.