1996 genetics essay ap biology
Did you eat cereal for breakfast or tomatoes in your dinner salad? Do you know someone who has received gene therapy to treat a disease such as cancer? Should your school, health insurance provider, or employer have access to your genetic profile? Understanding how DNA works has allowed scientists to recombine DNA molecules, clone organisms, and produce mice that glow in the dark.
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Did you eat cereal for breakfast or tomatoes in your dinner salad? Do you know someone who has received gene therapy to treat a disease such as cancer? Should your school, health insurance provider, or employer have access to your genetic profile?
Understanding how DNA works has allowed scientists to recombine DNA molecules, clone organisms, and produce mice that glow in the dark. We likely have eaten genetically modified foods and are familiar with how DNA analysis is used to solve crimes. Manipulation of DNA by humans has resulted in bacteria that can protect plants from insect pests and restore ecosystems. Biotechnologies also have been used to produce insulin, hormones, antibiotics, and medicine that dissolve blood clots.
Comparative genomics yields new insights into relationships among species, and DNA sequences reveal our personal genetic make-up. However, manipulation of DNA comes with social and ethical responsibilities, raising questions about its appropriate uses. Nucleic acids can be isolated from cells for analysis by lysing cell membranes and enzymatically destroying all other macromolecules. Fragmented or whole chromosomes can be separated on the basis of size base pair length by gel electrophoresis.
Recombinant DNA technology can combine DNA from different sources using bacterial plasmids or viruses as vectors to carry foreign genes into host cells, resulting in genetically modified organisms GMOs. Transgenic bacteria, agricultural plants such as corn and rice, and farm animals produce protein products such as hormones and vaccines that benefit humans. It is important to remind ourselves that recombinant technology is possible because the genetic code is universal, and the processes of transcription and translation are fundamentally the same in all organisms.
Cloning produces genetically identical copies of DNA, cells, or even entire organisms reproductive cloning. Genetic testing identifies disease-causing genes, and gene therapy can be used to treat or cure an inheritable disease. However, questions emerge from these technologies including the safety of GMOs and privacy issues. A Learning Objective merges required content with one or more of the seven Science Practices. The Science Practice Challenge Questions contain additional test questions for this section that will help you prepare for the AP exam.
These questions address the following standards: [APLO 3. Begin the discussion with the ethical considerations, such as genetic modified foods, the availability of a genome to the government or insurance provider, or modifying a genome for therapy or the sex selection with embryos. These topics will be in the minds of students, so get them out in front and then get into the mechanics of the topic. Biotechnology is the use of biological agents for technological advancement.
Biotechnology was used for breeding livestock and crops long before the scientific basis of these techniques was understood. Since the discovery of the structure of DNA in , the field of biotechnology has grown rapidly through both academic research and private companies. The primary applications of this technology are in medicine production of vaccines and antibiotics and agriculture genetic modification of crops, such as to increase yields. Biotechnology also has many industrial applications, such as fermentation, the treatment of oil spills, and the production of biofuels.
To understand the basic techniques used to work with nucleic acids, remember that nucleic acids are macromolecules made of nucleotides a sugar, a phosphate, and a nitrogenous base linked by phosphodiester bonds. The phosphate groups on these molecules each have a net negative charge. An entire set of DNA molecules in the nucleus is called the genome. DNA has two complementary strands linked by hydrogen bonds between the paired bases. The two strands can be separated by exposure to high temperatures DNA denaturation and can be reannealed by cooling.
Various techniques are used to extract different types of DNA Figure Most nucleic acid extraction techniques involve steps to break open the cell and use enzymatic reactions to destroy all macromolecules that are not desired such as degradation of unwanted molecules and separation from the DNA sample.
Macromolecules are inactivated using enzymes such as proteases that break down proteins, and ribonucleases RNAses that break down RNA. The DNA is then precipitated using alcohol. Human genomic DNA is usually visible as a gelatinous, white mass. RNA analysis is performed to study gene expression patterns in cells. RNA is naturally very unstable because RNAses are commonly present in nature and very difficult to inactivate.
Because nucleic acids are negatively charged ions at neutral or basic pH in an aqueous environment, they can be mobilized by an electric field. Gel electrophoresis is a technique used to separate molecules on the basis of size, using this charge.
The nucleic acids can be separated as whole chromosomes or fragments. The nucleic acids are loaded into a slot near the negative electrode of a semisolid, porous gel matrix and pulled toward the positive electrode at the opposite end of the gel.
Smaller molecules move through the pores in the gel faster than larger molecules; this difference in the rate of migration separates the fragments on the basis of size.
There are molecular weight standard samples that can be run alongside the molecules to provide a size comparison. Nucleic acids in a gel matrix can be observed using various fluorescent or colored dyes. Distinct nucleic acid fragments appear as bands at specific distances from the top of the gel the negative electrode end on the basis of their size Figure A mixture of genomic DNA fragments of varying sizes appear as a long smear, whereas uncut genomic DNA is usually too large to run through the gel and forms a single large band at the top of the gel.
Although genomic DNA is visible to the naked eye when it is extracted in bulk, DNA analysis often requires focusing on one or more specific regions of the genome. PCR is used for many purposes in laboratories, such as the cloning of gene fragments to analyze genetic diseases, identification of contaminant foreign DNA in a sample, and the amplification of DNA for sequencing. More practical applications include the detection of genetic diseases.
This process is called reverse transcription. This requires the presence of an enzyme called reverse transcriptase. Deepen your understanding of the polymerase chain reaction by clicking through this interactive exercise. Nucleic acid samples, such as fragmented genomic DNA and RNA extracts, can be probed for the presence of certain sequences. Short DNA fragments called probes are designed and labeled with radioactive or fluorescent dyes to aid detection.
Gel electrophoresis separates the nucleic acid fragments according to their size. The fragments in the gel are then transferred onto a nylon membrane in a procedure called blotting Figure The nucleic acid fragments that are bound to the surface of the membrane can then be probed with specific radioactively or fluorescently labeled probe sequences.
When DNA is transferred to a nylon membrane, the technique is called Southern blotting , and when RNA is transferred to a nylon membrane, it is called northern blotting. Southern blots are used to detect the presence of certain DNA sequences in a given genome, and northern blots are used to detect gene expression. Cloning small fragments of the genome allows for the manipulation and study of specific genes and their protein products , or noncoding regions in isolation.
In cloning, the plasmid molecules can be used to provide a "folder" in which to insert a desired DNA fragment. Plasmids are usually introduced into a bacterial host for proliferation. In the bacterial context, the fragment of DNA from the human genome or the genome of another organism that is being studied is referred to as foreign DNA , or a transgene, to differentiate it from the DNA of the bacterium, which is called the host DNA.
Plasmids occur naturally in bacterial populations such as Escherichia coli and have genes that can contribute favorable traits to the organism, such as antibiotic resistance the ability to be unaffected by antibiotics. Plasmids have been repurposed and engineered as vectors for molecular cloning and the large-scale production of important reagents, such as insulin and human growth hormone. An important feature of plasmid vectors is the ease with which a foreign DNA fragment can be introduced via the multiple cloning site MCS.
The MCS is a short DNA sequence containing multiple sites that can be cut with different commonly available restriction endonucleases. Restriction endonucleases recognize specific DNA sequences and cut them in a predictable manner; they are naturally produced by bacteria as a defense mechanism against foreign DNA.
Many restriction endonucleases make staggered cuts in the two strands of DNA, such that the cut ends have a 2- or 4-base single-stranded overhang. In this way, any DNA fragment generated by restriction endonuclease cleavage can be spliced between the two ends of a plasmid DNA that has been cut with the same restriction endonuclease Figure Plasmids with foreign DNA inserted into them are called recombinant DNA molecules because they are created artificially and do not occur in nature.
They are also called chimeric molecules because the origin of different parts of the molecules can be traced back to different species of biological organisms or even to chemical synthesis. Proteins that are expressed from recombinant DNA molecules are called recombinant proteins. Not all recombinant plasmids are capable of expressing genes.
The recombinant DNA may need to be moved into a different vector or host that is better designed for gene expression. Plasmids may also be engineered to express proteins only when stimulated by certain environmental factors, so that scientists can control the expression of the recombinant proteins. You are working in a molecular biology lab and, unbeknownst to you, your lab partner left the foreign genomic DNA you are planning to clone on the lab bench overnight instead of storing it in the freezer.
As a result, it was degraded by nucleases, but still used in the experiment. The plasmid, on the other hand, is fine. What results would you expect from your molecular cloning experiment? Cloning can be used to quickly replicate crop plants that have advantageous genes, such as greater disease resistance or greater fruit production. However, cloning also produces crop plants that have little genetic variation.
In a group, discuss the advantages and disadvantages of using clones as human food sources in an era where the Earth is undergoing a period of climate change.
How well will cloned populations of crop plants be able to adapt to climate change, compared to non-clone crop plants? How would a scientist introduce a gene for herbicide resistance into a plant, such as corn? Suggested group size for the activity is 3—6 students.
Guide student groups to think about climate change as a natural selection pressure that will affect the success of the clones. By using crop plants with little genetic variation, there is little potential that these plants to withstand an environmental change such as rapid, human-induced global warming. The activity is an application of Learning Objective 3.
An expanded lab investigation for biotechnology, involving performing a genetic transformation on E. Genetic engineering is as old as farming. Discuss the efforts that were made by farmers to develop better crops before technology gave its assistance. Discuss how technology has increased the changes in crops worldwide. Unicellular organisms, such as bacteria and yeast, naturally produce clones of themselves when they replicate asexually by binary fission; this is known as cellular cloning.
The nuclear DNA duplicates by the process of mitosis, which creates an exact replica of the genetic material. Reproductive cloning is a method used to make a clone or an identical copy of an entire multicellular organism. Most multicellular organisms undergo reproduction by sexual means, which involves genetic hybridization of two individuals parents , making it impossible for generation of an identical copy or a clone of either parent.
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