Part+2


 *  [[image:MicroArrays1.jpg align="right"]]Microarrays **

**Describe:** A microarray is a microscope slide on which copies of single-stranded DNA fragments from the organism's gene. Many tiny fragments of a lot of single-stranded DNA fragments that represent a different genes make up a DNA microarray. On a tightly space array, these different genes are fixed to a glass slide.

**Analyze:** DNA fragments on a microarray are tested for hybridization with cDNA molecules. To do this mRNA is isolated and cDNA is made by reverse transcriptase using florescent nucleotides. The cDNA goes on the microarray with a different gene in each spot. It then hybridizes with any complementary DNA on the microarray. The excess cDNA rinses off, and the microarray is scanned for fluorescence and each fluorescent spot represents a gene that is expressed in the tissue sample.

**Apply:** Researches are able to figure out a what stage in life an organism expresses certain genes. It also helps them to compare patterns of gene expression like in breast cancer. Comparing the patterns of gene expression of noncancerous and cancerous breast cancer tumors has resulted in more effective treatment protocols.

**Synthesize:** A DNA microarray reminds me of a computer chip because both store information. Many different tiny fragments of different things make up both of them. DNA microarrays and computer chips are also both really small, yet hold such valuable information.

**Argue:** This is a positive thing because they help contribute to a better understanding of diseases. It may show new diagnostic therapies or techniques. DNA microarrays will also provide a bigger picture of how genes interact to form an organism and maintaining its vital systems. Other advantages include how fast it is, it is relatively cheap to use, and it is user friendly.

[|DNA Microarray]

**Sources:** AP Biology Textbook, http://arabidopsis.info/students/microarrays/advantages.html

**Gel Electrophoresis **

**Describe:** A gel made of a polymer acts to separate nucleic acids or proteins from either DNA or RNA.The strands are separated into different lengths. Groups of pieces of the nucleic acids or proteins that are the same shape form bands.

**Analyze:** After the gel separates the nucleic acids, they move toward a positive pole. The shorter pieces move farther than longer pieces because they can move through the fibers of the gel much easier. Bands containing the same length pieces can then be compared. Gel electrophoresis needs a linear strand of either DNA or RNA, a polysaccharide gel and an electrical source.

**Apply:** An application of gel electrophoresis is called restriction fragment analysis. This provides useful information about the DNA segments. It is also helpful when comparing 2 different DNA pieces. It can easily compare alleles of a gene.

**Synthesize:** When I think of this process I think of two different size animals, one very big and one very small. They are going to race through a forest and see who can get through it first. The smaller one wins because it can get farther faster because it is able to maneuver through all the trees and other obstacles.

**Argue:** This is a positive thing because it can be used for many things. It can be used in criminal investigations. If they have a sample of blood or hair as evidence they are able to do this process on it to figure out who committed the crime. This process is also used in paternal testing to figure out or confirm the father of a baby. It is an extremely useful technique.

Gel Electrophoresis Animation

**Sources:** AP Biology Textbook, http://www.molecularstation.com/molecular-biology-techniques/gel-electrophoresis/

**Southern Blotting ** **Analyze:** This process occurs differently in heterozygotes than it does in homozygotes for a normal allele. There are 5 steps to this process. The first step is the preparation of restriction fragments. Second, gel electrophoresis takes place. The third step is blotting. The solution must be blotted. The single-stranded DNA that is stuck to the paper after is complementary to the bands of DNA in the gel. The next step is hybridization with the radioactive probe. The final step is an autoradiography. In this step a sheet of photographic film is put over the paper blot. The result is a formed image on the sheet of film. **Apply:** It can be used in gene discovery, mapping, evolution, development studies and even in forensics. It can help us identify bands of DNA segments that contain the beta-globin gene. It's used to identify carriers of mutant alleles. **Synthesize:** The process of southern blotting makes me think of photography class and processing a roll of film. On a roll of film the pictures are not visible to our eye. The film needs to be processed in the right solutions and lighting. First, the film needs to be cut and then rolled into a canister. Then, special solutions need to be applied to it to make the pictures show up. Once that's done pictures can be printed and they are now visible to our eye. **Argue:** This is a positive thing because it can detect carriers of mutant alleles. It can be used to prevent the spread of mutations and diseases. It's important to know of this process because if two people discover that one of them carries the mutant allele, they might decide to not reproduce in order to avoid certain complications in their offspring. media type="custom" key="8276558" **Sources:** AP Biology Textbook, http://www.accessexcellence.org/RC/VL/GG/ecb/southern_blotting.php
 * Describe:** Southern blotting is a combination of two processes we have previously talked about which include gel electrophoresis and nucleic acid hybridization. It has to do with the bands that are the result of gel electrophoresis**.** The probe in this process is a radioactive single-stranded DNA which is complementary to the gene of interest.