Tuesday, March 15, 2011

CH. 15, 16, 21

Connections
1. Viruses multiply via a process called the Lysogenic Pathway. In this process, viruses cut into the chromosomal DNA of a host cell and integrate its viral genes with that of the host. If that cell were a prokaryote, once it divided through binary fission, when cell wall material is deposited at the middle section of the cell to sever the cytoplasm, the replicated DNA, which also contained the viral DNA, manifest themselves in the creation of new infectious viruses.

2. The plasmid is the bacterial unit of DNA that contains genes that enable the transfer of genetic material between two cells. This process, which is called conjugation, causes a recipient cell to integrate foreign genetic material with its own genetic material, and, as a result, replicate the foreign DNA. The incorporating of external and internal genetic material will result in the recipient bacteria cell expressing new or alternated traits, in all called Bacterial Transformation.

3. A plasmid is the circle of DNA that is self-replicating and present in bacteria cells. When this genetic material becomes corrupted when the incorporation of DNA of an infective virus occurs, its self-replicating nature will benefit the virus because it only helps its proliferation. If this was a RNA retrovirus, the organism infected could express deadly diseases such as AIDS, for HIV is a retrovirus that destroys certain white blood cells, and, as a result, the immune system as a whole.

4. The prokaryotic organism E. Coli,, which resides in the large intestines of various mammals, feeds off the nutrients consumed by the host organism, If it infects the digestive system of a human baby ,for example, glucose is not as readily provided as lactose sugar from milk. In order to digest this hydrolysis composed disaccharide, E. Coli utilizes operator to regulate the production of the enzymes that breack down lactose. Operators serve as binding sites for repressor proteins that disable the transcription of the gene coding for lactose enzymes.

5. Okazaki fragments are disconnected DNA segments complimentary to the 5'->3' DNA parent strand that result from the discontinuous replication process of DNA polymerase on the lagging strand. Similarly restriction enzymes create fragmented DNA strands by cutting specific sequences on strands so that the genetic material of another organism can be incorporated by occupying the gaps. Both the Okazaki segments and the segments of restriction enzymes rely on the protein Ligase to consolidate the nicks and little openings resulting from fragmentation.

III. Essentials
1. The first stage of gene regulation is before transcription, for in the nucleus, before a DNA molecule is transcribed it can become attached to acetyl groups that loosen the grip of histones for an activating function, or inhibitory methyl groups which block an allele's expression on a trait. The second stage is after transcription in which an mRNA needs to exit the nucleus, for before traveling to the ribosomes certain proteins termed Y-boxed proteins can be binded to the transcript to completely stop its translation, in other words leaving it inactivated.

The third stage of regulation takes place during translation, for due to the fact that the longer a transcript lasts in the cytoplasm the more times it can be translated, enzymes digest and remove transcripts at certain times. The last stage is after translation because various factors can inhibit or activate a new protein, as seen by Y-box proteins that are only activated when a phosphate group is bonded to them by enzymes.


2. *This will be included in the notecards that get turned in later*

3. Prior to gel electrophoresis, a single-stranded DNA template is placed in a mixture containing the necessary enzymes, nucleotides, etc. to produce new strands of DNA. The numerous new copies of DNA fragments that have been produced are then separated from each other through the gel electrophoresis process, in which fragments pass through a semisolid gel slab in response to an electric field. Because each fragment's end is fluorescent-tagged, as they move through the gel and become subject to a laser, a computer can subsequently record what specific color the fragments express, and since the colors correspond to specific nucleotides a DNA sequence can thus be concluded (DNA fingerprint).

4. The primary difference between eukaryotic and prokaryotic genomes is the DNA of eukaryotes is linear whereas in prokaryotes it is circular (plasmids). In addition, the method in which prokaryote cells divide is very different when compared to mitosis. Known as prokaryotic fission, this process begins with the replication of DNA. Following duplication, the genetic materials attach to the cell's plasma membrane. Using newly produced lipids and proteins, the cell adds the molecules to the membrane to separate the attached strands, thereby stretching the length of the cell and the DNA attached to its walls. The cell finally undergoes  cytokinesis by depositing cell membrane material in the midsection of the now elongated cell, soon resulting in a new membrane being formed.

5. The lytic pathway is a variation cycle of how viruses multiply from cells. In the lytic cycle, viruses inject their genetic material in a host cell so that new viral particles can be synthesized within the cell. These infectious agents are released from the host after it goes through the process lysis, when the cell dies. This pathway is different from the lysogenic cycle in that it is relatively quicker since the lysogenic cycle is essentially an extension of the lytic pathway. Instead of just killing the cell, the lytic cycle focuses on incorporating the viral DNA with the genetic material of the host cell, so that when that cell divides, the foreign DNA will successfully spread, resulting in proliferation of the viruses.

Tuesday, March 8, 2011

Ch. 13 and 14

II. Connections
1. 5', or five prime end refers to the fifth carbon of the deoxyribose sugar of DNA, which is bonded to a phosphate molecule. This is a covalent bond  due to the electronegativities of the two molecules being relatively equal and therefore resulting in shared electrons. However, if one molecule's electronegativity is substantially greater than that of another, then the bond would not be covalent but ionic.

2. mRNA is read by ribosomal subunits via a method in which the nitrogen bases are read by translating them into amino acids three bases at a time, one group of three bases being termed a 'codon'. The codon containing the nitrogen bases Adenine, Uracil, and Guanine is known as the start codon and it signals the ribosomes to begin translating the mRNA three at a time as soon as it is read, which is why the start codon is found at the beginning of transcipts. Once the 'start codon' is read and the mRNA is translated into proteins, each codon that is read corresponds to a specific amino acid, and ultimately each transcript results in a unique expression of the specific codons collectively. No codon is dominant in determining the outcome of the protein which is relevant to genetic incomplete dominance because codons are expressed as a mixture of different amino acids.

3. Semiconservative refers to one of the theoretical methods that DNA is replicated in every cell, stating that two copies of DNA are ultimately produced, each one containing one original strand and one newly synthesized strand. This replication would be hampered in females if that one specific DNA strand was an x-chromosome destined to be inactivated and remain a Barr Body, for such restricts one of a female’s x-chromosomes from extending out of its condensed chromatin form and therefore disables the replication of that DNA in every cell.

4.  The enzyme RNA polymerase is a protein that catalyzes ribonucleotides in a new RNA strand by utilizing one strand of DNA as a template. The RNA molecule that is created during this process leaves the nucleus to be translated into proteins by ribosomes, whose subunits are also synthesized in the nucleolus in the nucleus.

5. DNA polymerase is an enzyme that is a protein that replicates DNA by catalyzing free nucleotides to each new strand of deoxyribonucleases on to a original strand belonging to the parent DNA. These deoxribose sugars are bonded to the nucelotides by glycosidic linkages..

6. The process of DNA replication begins with the helicase enzyme which unzips the two strands of DNA by breaking the hydrogen bonds between the DNA’s nitrogen base pairs. As a whole this process of replication is similar to s-phase of the cell cycle which results in the doubling of the amount of a cell's chromesomes, as a karyotype, which is a digital image of chromosomes, of a cell in the following G2 stage of the cell cycle would relate to the DNA replication.


III. Essentials

1. Because the two strands of DNA molecule are antiparallel, the enzyme DNA helicase can only assemble new nucleotide strands in the 5'-3' direction. Despite this, assembly is discontinuous where nucleotides of a 3'-5' strand are only joined to exposed -OH functional groups that are themselves connected to the 3' carbon of a growing strand.  Despite the choppy DNA strand, the enzyme ligase initiates the integration of all short stretches of strand.

2. -RNA is composed of only strand of nucleotides, while DNA consists of two.
 -RNA nucleotides contain the sugar ribose whereas DNA's have the sugar deoxyribose.
- one of DNA’s nitrogen bases is labeled thymine, while RNA's version of the same base is called uracil.

3. -mRNA (messenger RNA) is the class of RNA that contains the recipe for the construction of proteins. They are the outcome of the transcription process of protein synthesis centered in the nucleus.

    -tRNA (transfer RNA) is the type of RNA that serves as a transport of amino acids to ribosomes for the production of proteins. They arrange themselves in alignments which the mRNA specifies.

   - rRNA (ribosomal RNA) is the of RNA molecules that becomes a vital part of ribosomes, because they provide for the decoding of mRNA and assist tRNA in translation.


4. A.Transcription- In the process of transcription, the enzyme RNA polymerase reads a template strand of DNA and synthesizes a new complimentary strand, after recognizing the start signal of a promoter or specific base sequence.

B. RNA Splicing- Before mRNA molecule leaves the nucleus to be translated by ribosomes, it must be modified or spliced by which introns or base sequences that don't code for proteins are 'snipped' and exons or protein-coding base sequences are retained.

C. Translation- When a ribosome initiates the translation phase, it reads a mRNA strand three base sequences at a time. Each series of three bases, or codon, corresponds to a specific amino acid which are delivered by tRNA, who in addition carry the anticodon base pairs that are complementary to those of the mRNA. The creation of the protein, or polypeptide from the ribosome is called elongation.