AP BIO MIDTERM ESSAYS
Describe two ways that the reflex arc differs from typical stimulus-response transmission pathways. Provide reasoning to support the claim that reflex arcs help organisms avoid serious injury.
Two ways that the reflexes arc differs from typical stimulus response transmission pathways are a quicker response time and fewer neurons are used. This is so that there is a quicker response to a threat.
Describe how a plasmid can be genetically modified to include a piece of foreing DNA that alters the phenotype of bacterial cells transformed with the modified plasmid. Describe a procedure to determine which bacterial cells have been successfully transformed.
A plasmid can be genetically modified to include a piece of foreign DNA that alters the phenotype of bacterial cells transformed by the modified plasmid by cleaving DNAs. This process uses restriction enzymes to cut the plasmid and inserted DNA, and both must use the same restriction enzyme. The cutting produces sticky ends, which are ends of DNA that have a staggered cut and matching ends bond with each other. The joining of sticky ends is called Ligase. The correct orientation of insertion should be done to the bacterial cells to ensure proper expression. The gene of interest should be attached with a promoter. The reporter gene, a gene used to identify insertion of desired DNA, should be inserted to DNA with a gene that produces a new phenotype. The selective marker is inserted to help identify the DNA insertion. The AUG should be in place to ensure proper start codon. The bacterial cell uptakes plasmids and undergoes transformation. This starts with isolation, plasmids are isolated and the agar plate grows only colonies of resistance gene. Next is the use of antibiotic resistance. Gel electrophoresis isolates the plasmids and the step after is retrieval, taking of the altered plasmid.When the modified plsmid is taken by the bacteria, their protein produces glowing light and this ensures proper retrieval. The use of a fluorescent marker, called tagging, reveals the glowing protein.
Identify a likely primary function of each cell type and explain how the data supports the identification.
Cell type X has locomotion and uses cilia for it. It uses mitochondria for energy to provide movement. Cell type Y goes through protein synthesis, since it has large amounts of rough ER and Golgi Bodies to produce and package proteins. Cell type Z could have no function or is a dead cell going through apoptosis and it does not require these organelles.
Explain the most likely genetic change that produced the polypeptide in species 2 and the most likely genetic change that produced the polypeptide in species 3. Predict the effects of the mutation on the structure and function of the resulting protein in species 4. Justify your prediction.
In species 3, the genetic change could've happened due to a substitution and resulted in an amino acid change only at position 4. For species 3, a deletion could've happened, which resulted in the termination of the polypeptide after the Val at position 8. A protein may have a different structure and a change in functions. A change in amino acid sequence of the protein starting at position 5 could alter the overall structure or local structural regions, interfering with function of the protein.
Describe two potential biological risks of large-scale cultivation and use of such genetically modified plants.
Two risks of large-scale cultivation and use of genetically modified plants are herbicides and disruption of food chain. Herbicides harm non-target species, and organic alternative herbicides could be used instead. When the food chain is disrupted, providing an alternative food source could be a solution.
Describe the structure and function of the parts of a eukaryotic chromosome. Describe the adaptive significance of organizing genes into chromosomes. How does the function and structure of the chromosome differ in prokaryotes?
The structure of the Eukaryotic chromosome is condensed DNA to fit more in the nucleus. The DNA codes for proteins or for RNA. The DNA are in twisted loops, which go around the nucleosomes, which then loop again and again. The histones order the DNA into nucleosomes. All of this allows for more space. Chromosomes have Telomeres to protect against degradation and limits the number of cell division. The Significance of organizing genes into chromosomes allows for genetic variation, gene regulation, and complexity. This leads to variation in gametes, offsprings getting the same number of chromosomes, maintaining the integrity of the chromosomes, histone acetylating, methylation, allows for more genes, and evolution new genes can occur. The function and structure of the chromosome differ in prokaryotes. They have a different shape, the bacteria has a circular shape and is less complex (doesn't contain histones, no folding). Both have different sizes and the bacteria has fewer genetic information.
Identify four organelles that should be present in the eukaryotic organism and describe the function of each organelle. For three organelles identified in part a, explain how prokaryotic cells carry out the associated functions. Describe three observations that support the endosymbiotic theory.
Four organelles the Eukaryotic organism has are the Nucleus, Ribosomes, Mitochondria, and Vacuoles. The Nucleus carries hereditary information and ribosomes are the place of protein production. the mitochondria synthesizes ATP and vacuoles store water and waste. Instead of a nucleus and just DNA, bacterial cells have plasmids floating around in the cell, but isn't the main type of DNA. Bacteria don't have membrane bound organelles. The endosymbiotic theory is the belief that prokaryotic cells have been engulfed by Eukaryotes and are in a symbiotic relationship. Evidence of this are that mitochondria and chloroplasts have separate DNA from the cell and are the same size as a prokaryotic cell.
Describe three types of chemical bonds/interactions found in proteins. For each type, describe its role in determining protein structure. Discuss how the structure of a protein affects the function of two of the following: Muscle contraction, regulation of enzyme activity, and cell signaling. Explain the genetic bases of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the world.
Proteins use hydrogen bonds, peptide bonds, and disulfide bonds. hydrogen bonds are its interactions with oxygen and nitrogen and is used in all but the first level structure of an amino acid. Peptide bonds link amino acids together and is used in the primary structure. Disulfide bonds use two sulfur atoms for bonding and is found in the quaternary or tertiary structure. Protein structure affects muscle contraction and enzyme activity. It affects muscle contraction by the ATP/ADP changes in the myosin structure and troponin/tropomyosin interaction blocks binding of myosin to actin. Enzyme activity is affected by protein structure through temperature or pH changes and through binding of the allosteric activator. The genetic basis of the abnormal hemoglobin is the changing of glutamine to valine and is the point mutation in DNA. The sickle cell allele is selected for in certain areas of the world since it protects against malaria and its heterozygotes maintain a reproductive advantage.
Explain the role of each of the following in protein synthesis in eukaryotic cells: RNA polymerase, spliceosomes, codons, ribosomes, and tRNA. Discuss two specific mechanisms of protein regulation in eukaryotic cells. Select a specific virus or type of virus and explain how it deviates from the central dogma.
RNA polymerase in Eukaryotic cells transfers DNA to RNA. Spliceosomes remove the introns and connects the exons in the RNA. Codons code for amino acids. Ribosomes are the site of protein synthesis. tRNA transports amino acids. Two specific mechanisms of protein regulation in Eukaryotic cells are the promoter and the enhancer. The promoter increases RNA polymerase binding and the enhancer increases transcription. The CHikungunya virus's RNa enters the host and uses their body to make more of their RNA coding. They use their ribosomes to make RNA.
Describe the role of three of the following in the regulation of protein synthesis: RNA splicing, repressor proteins, methylation, and siRNA. Describe three different types of mutations and their effect on protein synthesis. Identify two environmental factors that increase the mutation rate in an organism, and discuss their effect on the genome of the organism. Describe on example of epigenetic inheritance.
RNA splicing in the regulation of protein synthesis splices exons together and removes introns. Methylation prevents transcription and protects against cleaving of restriction enzymes. Repressor proteins inhibit transcription and translation and inactivate gene expression. A silent mutation changes a nucleotide and its effect is no change in the amino acid/protein sequence. A deletion removes a segment of the chromosome and alters gene expression. A frameshift mutation happens when a nucleotide insertion/deletion alters the reading frame and it changes the amino acid/ protein sequence. Two environmental factors that increase the mutation rate in an organism are viruses and radiation. Viruses embed their own DNA into the host's cells and this disrupts the gene sequence. Radiation damages/alters DNA. An example of epigenetic inheritance is the Agouti mice experiment. The mice were either given BPA or gemistein, which is high in methyl groups. Those fed with BPA had an increased expression of the Agouti gene and they had a higher weight and a yellow coat color. The mice who were fed Gemistein had a decreased expression of the Agouti gene and had a lower weight and a brown coat color.
Describe the structure and function of two eukaryotic membrane-bound organelles other than the nucleus. Describe the function of two of the following and discuss how each differs in prokaryotes and eukaryotes: DNA, Cell wall, Ribosomes. Explain the endosymbiotic theory of the origin of eukaryotic cells and discuss an example of evidence supporting this theory.
The mitochondria's structure has many infoldings within the organelle and its function is to release chemical energy and produce ATP. The Golgi Apparatus has a series of flattened sacs and its function is to package and process molecules. The DNA in Prokaryotic and Eukaryotic cells contain genetic information, but Prokaryotes have a circular DNA and don't have histones. Both cells use the cell wall for support and protection, but in Eukaryotes, the cell wall is made out of cellulose or chitin and in Prokaryotes, the cell wall is made out of Peptidoghycans. For both cells, the ribosome is used for making proteins and is the site of translation. The difference in both is that the ribosomes for Eukaryotes are larger and in Prokaryotes, the ribosome is smaller and contains different proteins or RNAs. The Endosymbiotic Theory is the belief that a prokaryotic cell was engulfed or absorbed by another cell and formed a symbiotic relationship by using it as an organelle. Evidences of this are that mitochondria and chloroplasts contain their own DNA and their own double membrane.
