Ap Biology Chapters 15, 16, and 21 Work

Derek Lee

Mr. Hillegas

Ap Biology

13 March 2011

Chapter 15, 16, and 21 Work

II. Connections

1.      Lysogenic and Binary Fission- During a lysogenic pathway, a virus does not kill its host outright, but rather a viral enzyme cleaves the host’s chromosomal DNA, then integrates the viral genes into its base sequence. The infected cell eventually divides, and replicates its DNA, including all of the foreign genes in the recombinant molecule, i.e. miniature time bombs are passed on to its descendents. These infected cells, viruses, may infect other bacterium, in which the virus will be passed on through the bacteria cells via binary fission, the replication of a prokaryotic cell.

2.      Conjugation and Bacterial transformation- Conjugation is a process that involves the transfer of genetic information from one bacterial cell to another, and requires physical contact between the two bacteria involved via a protein tube called an F or sex pilus, which is also the conduit for the transfer of genetic material. During transformation, bacteria will pick up DNA from their environment from a number of sources, most notably the remnants of DNA from dead bacterial cells. One way for this genetic material to be “picked” up is through conjugation – the physical touch and sex pilus.

3.      Plasmid and retrovirus- Retroviruses carry an enzyme causes a process known as reverse transcription in the DNA to occur. It fools the DNA to copy it rather than RNA leading to the creation of more retroviruses resulting in cells that carry the viruses for life and only further duplicate. Plasmids are small, self-replicating circles of DNA which show how such viruses can be passed on through conjugation and thus physical touch.

4.      Operator and hydrolysis- hydrolysis is a chemical reaction or process wherein a water molecule and a reactant exchange functional groups resulting in two end products. It is the process of splitting a compound into fragments with the addition of water, breaking down polymers into simpler units, i.e. starch into glucose. Operations are segments of DNA where the repressor binds to, thereby preventing the transcription of certain genes; both of which stop the chemical processes leading to the replication of DNA.

5.      Okazaki Fragments and restriction enzymes – Okazaki fragments are formed when the 5’ to 3’ end of the DNA adds grows from the top to bottom resulting in unconnected or Okazaki fragments. Restriction enzymes catalyze the cleave of DNA at restriction sites, producing small fragments for gene splicing, aiding the connection between the fragments.

III. Few Essentials

1.      At control before transcription the access to genes is under control. Where a DNA molecule is wound up tightly, polymerases cannot access genes. Acetylation can make histones loosen their grip and or a maternal or paternal allele at any locus in a diploid cell may become methylated which can block the gene’s influence on a trait. Such controls also affect how a gene will be transcribed, some gene sequences can be rearranged or multipled.

Controls of transcript processing influences mRNA transcript processing. Such examples include the nuclear envelope which helps control when mRNA transcript reaches a ribosome. The transcript can not pass through a nuclear pore complex unless proteins become attached to it. A base sequence in the untranslated end of mRNA is like a zip code.  Controls “read” the code and attach proteins to it. During translation certain controls work on initiation factors and ribosome components. Others work through mRNA transcript stability. Controls after translation is controlled by new enzymes and other proteins. For example, Y-box proteins become activated only when enzymes attach a phosphate group to them. Other controls activate, inhibit, and stabilize diverse molecules that take part in protein synthesis. Allosteric control of tryptophan synthesis is a case in point.

2.      Note card~

3.      Gel electrophoresis separates an individual’s DNA fragments from one another according to size. AN electric current repels a mixture of the negatively-charged DNA fragments thru microscopic pores in the gel from the negative to positive electrode. Upon completion, the separated fragments of DNA can be visualized as a ladder of small bands in the gel by staining with methylene blue dye solution. It is a procedure for separating a mixture of molecules through a stationary material (gel) in an electrical field.

4.      Eukaryotic cells divide through mitosis whereas prokaryotic cells divide through prokaryotic (binary) fission. Prokaryotic fission starts when a cell replicates its DNA. The parent molecule and the copy are both anchored to the plasma membrane at adjacent sites. Meanwhile, the cell is synthesizing proteins and lipids, which become added to the plasma membrane between the two attachment sites. The additions make the membrane grow, which moves the molecules of DNA apart. New wall material is deposited onto the growing membrane, and growth continues on through  the cell midsection. It cuts the cytoplasm in two, the result being two genetically equivalent daughter cells.

5.      The lytic cycle is one of two cyclecs of viral reproduction, which is usually considered as the main method of viral reproduction because it ends in lysis of the infected cell releasing the progeny viruses that will in turn spread and infect other cells. A virus undergoes lytic and lysogenic cycles to reproduce. The lytic cycle vs. lysogenic cycle takes place when the virus gets itself attached to the outcer cell wall of a bacterium. Then it releases enzymes to weaken the cell wall of the bacteria. Then, virus injects its genetic material, that is, either double stranded DNA or single stranded RNA, depending o the virus. The lytic cycle causes the host bacterium to undergo cell lysis or cell destruction whereas the lysogenic cycle does not cause the host to lysis. The lytic cycle can lead to the production of 100-200 progeny phages vs lysogenic in which the DNA of the phage gets integrated into the bacterial chromosome and no progeny are produced mostly. The lytic cycle can not be converted into the lysogenic cycle but the lysogenic cycle can be converted into the lytic cycle when the host cell is exposed to chemical or physical agents.