Test2HW - Karmelo Navalta (kan337) BIO325 March 29, 2008...

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Karmelo Navalta (kan337) BIO325 March 29, 2008 Chapter 6 Questions C2) Conjugation is a form of sexual reproduction because it involves direct physical interaction between two bacterial cells in which one bacterium acts as a donor and transfers genetic material from one bacterium to another. The transfer of genetic material through direct physical interaction is the definition of sexual reproduction. C9) The lytic cycle starts with the phage DNA injecting its DNA into the cytoplasm, then the phage DNA directs the synthesis of many new phages and coat proteins. These components then assemble to make new phages. When synthesis and assembly are completed, the bacterial host cell is lysed, released the newly made phages into the environment, which then can bind to new bacterial cells. The lysogenic cycle starts with a bacteriophage infects a bacterium. The bacteriophage that usually infects is called a temperate phage with do not produce new phages and will not kill the host bacterial cell. The phage then integrates its genetic material into the chromosome of the bacterium. The integrated phage DNA, called a prophage, can exist in a dormant state for a long time, during which no bacteriophages are made. When the bacterium containing a lysogenic prophage divides to produce two daughter cells, it copies the prophage’s genetic material along with its own chromosome. Thus, both daughter cells will inherit the prophage. At a later time, the prophage may become activated to excise itself to enter the lytic cell to promote the synthesis of new phages and eventually lyse the host cell. C13) First, a DNA fragment binds to a cell surface receptor. Then, an extracellular endonuclease cuts the DNA into smaller fragments. One strand is then degraded and a single strand, which contains the lac+ gene, is transported into the cell. The DNA strand aligns itself with a homologous region on the bacterial chromosome, where the lac- gene is. The DNA strand is incorporated into the bacterial chromosome via homologous recombination. The heteroduplex DNA is repaired in a way that changes the lac- strand to create a lac+ gene. Competent cells are bacterial cells that are able to take up DNA. C14)
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The transfer of conjugative plasmids such as F factor DNA C15) The uptake of DNA could provide the cell with a nutritional source and could also provide the cell with a new trait that might be beneficial for its survival. . E1) You know its not due to rare double mutations because there were no colonies of bio met phe+ thr+ or bio+ met+ phe thr – strains when 10^9 cells where plated alone E3) A U-tubed shape apparatus distinguishes between conjugation and transduction because of the pore size. The pores are too small for the passage of bacterial cells. But, viruses can pass through each side and infect cells on either side of the U-tube. DNA can also pass through also. E10)
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Test2HW - Karmelo Navalta (kan337) BIO325 March 29, 2008...

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