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AP Bio Exam: Unit 6
AP Exam
| Question | Answer |
|---|---|
| How is genetic information stored? | In the sequence of nucleotide bases (A, T, C, G) within DNA molecules. |
| How is genetic information passed from one generation to the next? | Through DNA replication and transmission of genetic material to offspring. |
| How is prokaryotic DNA shaped? | Circular chromosome found in the nucleoid region. |
| How is eukaryotic DNA shaped? | Linear chromosomes organized within a membrane-bound nucleus. |
| How is the amount of DNA different between a prokaryote and a eukaryote? | Eukaryotes generally have more DNA organized into multiple chromosomes. |
| What is a plasmid? | Small, circular, double-stranded DNA molecule separate from chromosomal DNA. |
| Identify two functions of plasmids. | Antibiotic resistance and virulence factors. |
| Identify two biotechnical uses for plasmids. | Gene cloning and recombinant protein production. |
| Why is DNA a better hereditary material than RNA? | DNA is more chemically stable due to deoxyribose sugar and lack of 2' OH group. |
| What are the nucleotide base pairing rules? | Adenine pairs with Thymine; Cytosine pairs with Guanine. |
| What is the structure of a purine? | Double-ring nitrogenous base structure. |
| Which of the nitrogenous bases are purines? | Adenine and Guanine. |
| What is the structure of a pyrimidine? | Single-ring nitrogenous base structure. |
| Which of the nitrogenous bases are pyrimidines? | Cytosine, Thymine, and Uracil. |
| Why does a purine always pair with a pyrimidine? | To maintain the uniform width of the DNA double helix. |
| If there is 20% thymine in a DNA strand, how much cytosine is there? | 30% (If T=20%, A=20%, leaving 60% for C+G, so C=30%). |
| What direction is DNA synthesized? | 5' to 3' direction. |
| What direction does the DNA polymerase READ the DNA template? | 3' to 5' direction. |
| What is the function of helicase? | Unwinds the DNA double helix at the replication fork. |
| What is the function of topoisomerase? | Relieves torsional strain ahead of the replication fork by cutting and rejoining DNA. |
| What is the function of DNA polymerase? | Synthesizes new DNA strand by adding nucleotides complementary to the template. |
| What is the function of RNA primers and primase? | Primase synthesizes RNA primers to provide a starting point for DNA polymerase. |
| Why are RNA primers required for DNA replication? | DNA polymerase cannot initiate synthesis de novo; it requires a free 3' OH group. |
| How does the leading and the lagging strand differ? | Leading strand synthesized continuously; lagging strand synthesized in Okazaki fragments. |
| What is the function of DNA ligase? | Joins Okazaki fragments on the lagging strand by forming phosphodiester bonds. |
| Describe the process of DNA replication using the enzymes described above. | Helicase unwinds, topoisomerase relieves stress, primase lays primers, polymerase extends, ligase seals fragments. |
| What determines RNA function? | Its nucleotide sequence and resulting 3D structure. |
| What is the function of mRNA? | Carries genetic information from DNA to the ribosome for protein synthesis. |
| What is the function of tRNA? | Transports specific amino acids to the ribosome during translation. |
| What is the function of rRNA? | Structural and catalytic component of ribosomes. |
| How does the mRNA, tRNA, and rRNA all interact? | mRNA codons pair with tRNA anticodons on the rRNA ribosome structure. |
| How does the DNA sequence determine the RNA sequence? | Through complementary base pairing during transcription (A-U, T-A, C-G, G-C). |
| What is transcription? | Process of synthesizing RNA from a DNA template. |
| What is the starting material for transcription? | DNA template strand. |
| What is the product of transcription? | A complementary RNA molecule (mRNA, tRNA, or rRNA). |
| What is the function of RNA polymerase? | Enzyme that synthesizes RNA by reading the DNA template strand. |
| Which strand is the template strand? | The strand transcribed by RNA polymerase; it is complementary to the mRNA. |
| Which direction does transcription take place? | RNA is synthesized 5' to 3'. |
| Which direction is the template strand READ? | 3' to 5'. |
| Describe the process that takes place during transcription. | RNA polymerase binds promoter, unwinds DNA, synthesizes RNA 5' to 3', and terminates. |
| Identify three post-transcriptional modifications that alter the pre-mRNA prior to its release from the nucleus. | 5' cap addition, 3' poly-A tail addition, and splicing of introns. |
| What is the function of the poly-A tail? | Protects mRNA from degradation and aids in ribosome binding and export. |
| What is the function of the GTP cap? | Facilitates ribosome binding and protects mRNA from degradation. |
| What is the function of RNA splicing? | Removes introns (non-coding regions) and joins exons (coding regions). |
| How can multiple proteins be synthesized from the same mRNA transcript? | Alternative splicing of exons creates different mRNA sequences. |
| What is translation? | Process of synthesizing a polypeptide from an mRNA template. |
| Where does translation take place? | At the ribosome. |
| How does the location of translation differ between a prokaryote and a eukaryote? | Prokaryotes: cytoplasm; Eukaryotes: cytoplasm or rough ER. |
| How does the location of translation affect gene expression in a prokaryote? | Allows transcription and translation to occur simultaneously. |
| How is a prokaryote able to translate concurrently with transcription? | Lack of nuclear membrane allows ribosomes to bind mRNA while it is being transcribed. |
| What are the three steps of translation? | Initiation, elongation, and termination. |
| What happens in the initiation step of translation? | Ribosomal subunits, mRNA, and initiator tRNA assemble at the start codon. |
| Where does translation start? | At the AUG start codon. |
| What is a codon? | Three-nucleotide sequence in mRNA that specifies a particular amino acid. |
| How many nucleotides make up a codon? | Three nucleotides. |
| What amino acid is coded by UAU? | Tyrosine. |
| What codons code for lysine? | AAA and AAG. |
| How are multiple codons able to code for the same amino acids? | Redundancy of the genetic code; multiple codons specify the same amino acid. |
| True or False: One codon can code for more than one amino acid. | False; codons are specific (non-overlapping). |
| What are the three sites found on a ribosome and what is their function? | A site (binding), P site (peptidyl transfer), E site (exit). |
| What happens in the elongation step of translation? | tRNAs deliver amino acids to the ribosome, and the polypeptide chain grows. |
| What happens in the termination step of translation? | Release factor binds stop codon, causing polypeptide release and ribosome disassembly. |
| What chemical process releases the growing polypeptide? | Hydrolysis of the bond between the polypeptide and tRNA in the P site. |
| How does the genetic code demonstrate common ancestry? | The code is nearly universal across all domains of life. |
| What is the central dogma? | DNA -> RNA -> Protein. |
| How does a retrovirus violate this process? | It uses reverse transcriptase to make DNA from RNA. |
| Identify two examples of retroviruses. | HIV and Rous sarcoma virus. |
| What is the function of reverse transcriptase? | Synthesizes DNA from an RNA template. |
| How does a virus incorporate its viral genome into a host genome? | Viral DNA integrates into host chromosome via integrase enzyme. |
| How does a virus form progeny viruses? | Host cell machinery replicates viral components, which assemble into new virions. |
| What are regulatory sequences? | Non-coding DNA regions that control the rate of transcription. |
| What is the promoter region? | DNA sequence where RNA polymerase binds to initiate transcription. |
| What is the TATA box? | Conserved promoter sequence crucial for binding transcription factors and RNA polymerase. |
| What is the enhancer region? | DNA sequence that binds transcription factors to enhance transcription initiation. |
| What are epigenetic changes? | Heritable changes in gene expression that do not alter the DNA sequence. |
| How is DNA modified to initiate transcription? | Methylation patterns are removed; acetylation opens chromatin structure. |
| How is DNA modified to inhibit transcription? | Methylation of cytosine bases typically represses transcription. |
| How are histones modified to initiate transcription? | Acetylation of histone tails loosens DNA packing, allowing transcription. |
| How are histones modified to inhibit transcription? | Deacetylation or methylation of histones condenses chromatin, blocking transcription. |
| True or False: All somatic cells have the same DNA. | True; differentiation is due to gene expression, not genetic content. |
| What is cell differentiation? | Process by which cells become specialized in structure and function. |
| Why can different phenotypes result from different levels of gene expression? | Different proteins are produced based on which genes are active. |
| What is the function of transcription factors? | Proteins that bind to DNA to regulate transcription (activate or repress). |
| How do gene products affect the phenotype of organisms? | Proteins determine cellular structures and functions, shaping traits. |
| How do the amount of gene products affect the phenotype of organisms? | Concentration of proteins influences the intensity of traits. |
| How is prokaryotic gene expression regulated? | Primarily through operons that control transcription of related genes. |
| What is an operon? | Cluster of genes transcribed together under the control of a single promoter. |
| What is a repressor? | Protein that inhibits transcription by binding to operator or promoter. |
| What is a promoter? | DNA region where RNA polymerase binds to start transcription. |
| Describe the interaction between repressors and promoters. | Repressors physically block RNA polymerase binding or movement. |
| How does the repressor interact with the promoter? | Binds to the operator site, overlapping the promoter to block polymerase. |
| Describe the lac operon. | Operon responsible for lactose metabolism in bacteria. |
| What happens when lactose is present in the lac operon? | Lactose binds repressor, inactivating it; transcription proceeds. |
| What happens when lactose is absent in the lac operon? | Repressor binds operator, blocking transcription of lactose-digesting enzymes. |
| Is the lac operon repressible or inducible? | Inducible; normally off but turned on by lactose. |
| Describe the trp operon. | Operon responsible for tryptophan synthesis in bacteria. |
| What happens when tryptophan is present in the trp operon? | Tryptophan acts as a corepressor, activating repressor to stop transcription. |
| What happens when tryptophan is absent in the trp operon? | Repressor is inactive; RNA polymerase transcribes genes for tryptophan synthesis. |
| Is the trp operon repressible or inducible? | Repressible; normally on but turned off by tryptophan. |
| How is eukaryotic gene expression regulated? | Complex regulation involving transcription factors, chromatin remodeling, and RNA processing. |
| How do transcription factors affect the binding at the promoter? | They recruit RNA polymerase and stabilize the initiation complex. |
| Describe the difference between a promoter or enhancer. | Promoter is near the gene; enhancer can be distant and loops to the promoter. |
| What is the function of transcription factors? | Regulate gene expression by binding to specific DNA sequences. |
| What is the function of RNA polymerase. | Synthesizes RNA from the DNA template. |
| What is the function of the promoter. | Site where transcription initiation machinery assembles. |
| How do negative regulatory molecules inhibit gene expression? | By blocking transcription factors or recruiting repressors. |
| Identify TWO negative regulatory molecules that inhibit gene expression. | Repressors and silencers. |
| Explain how negative regulatory molecules inhibit gene expression. | They prevent RNA polymerase binding or elongation. |
| What is differential gene expression? | Expression of different genes by cells with the same genome. |
| How can differential gene expression affect the cellular products? | Leads to production of specialized proteins (e.g., hemoglobin vs. insulin). |
| How can differential gene expression affect the cellular functions? | Determines cell type and role within the organism. |
| What is siRNA? | Small interfering RNA involved in RNA interference to degrade mRNA. |
| What is miRNA? | Micro RNA that regulates gene expression by binding to mRNA and inhibiting translation. |
| How do siRNA and miRNA affect gene expression? | They cause mRNA degradation or block translation, silencing specific genes. |
| What is a mutation? | Change in the nucleotide sequence of DNA. |
| Identify TWO examples of mutations. | Point mutations and frameshift mutations. |
| How can a mutation have a positive effect on the product produced? | May create a beneficial protein variant enhancing survival. |
| How can a mutation have a negative effect on the product produced? | May produce nonfunctional or harmful proteins. |
| How can a mutation have a neutral effect on the product produced. | May not change the amino acid sequence (silent mutation) or protein function. |
| What is a point mutation? | Mutation affecting a single nucleotide pair. |
| What are the three types of substitution point mutations? | Silent, missense, and nonsense. |
| How does a silent mutation affect the protein product? | No change in amino acid sequence; protein function usually unaffected. |
| How does a silent mutation affect the amount of the protein product? | Usually no effect on amount. |
| How does a missense mutation affect the protein product? | Changes one amino acid, potentially altering protein structure/function. |
| How does a missense mutation affect the amount of the protein product? | Usually no effect on amount, but may affect stability. |
| How does a nonsense mutation affect the protein product? | Creates a premature stop codon, resulting in a truncated, often nonfunctional protein. |
| How does a nonsense mutation affect the amount of the protein product? | Often reduces amount due to mRNA degradation (nonsense-mediated decay). |
| What is a frameshift mutation? | Insertion or deletion of nucleotides that shifts the reading frame. |
| What happens if an insertion or deletion occurs at a nucleotide base pair? | Alters the codon sequence downstream, changing all subsequent amino acids. |
| How does an insertion or deletion affect the protein product? | Produces a nonfunctional protein with an incorrect amino acid sequence. |
| How does an insertion or deletion affect the amount of the protein product? | May reduce amount if mRNA is degraded or protein is unstable. |
| What causes errors in DNA replication? | Spontaneous errors by DNA polymerase or chemical damage. |
| What is involved in the cell’s DNA repair mechanisms? | Enzymes that detect and correct damaged or mismatched nucleotides. |
| How can a mutation be detrimental? | Reduces organism's fitness or survival. |
| How can a mutation be beneficial? | Increases organism's fitness or survival. |
| How can a mutation be neutral? | Has no effect on organism's fitness. |
| What is the cause of new genetic variation? | Mutations, sexual reproduction, and genetic recombination. |
| Identify an error in mitosis that leads to a change in phenotype. | Nondisjunction leading to aneuploidy. |
| Identify an error in meiosis that leads to a change in phenotype. | Nondisjunction leading to gametes with abnormal chromosome numbers. |
| What does it mean if an organism is a triploid? | Organism with three sets of chromosomes (3n). |
| How do triploids form? | Fusion of a diploid gamete with a haploid gamete. |
| Why is a triploid organism usually sterile? | Meiosis fails due to uneven pairing of homologous chromosomes. |
| Describe how the change in chromosome structure leads to genetic disorders. | Deletions, duplications, inversions, or translocations disrupt gene function. |
| How does a change in genotype affect the phenotype? | Alters protein production, which influences traits. |
| True or False: Natural selection acts on genotype. | False; natural selection acts directly on phenotypes. |
| How does a genetic change enhance survival? | By producing traits that improve adaptation to the environment. |
| How does natural selection affect phenotypes? | Increases frequency of advantageous phenotypes over time. |
| How does natural selection affect genotypes? | Indirectly increases frequency of alleles coding for advantageous traits. |
| What is horizontal transfer? | Transfer of genetic material between organisms other than by vertical reproduction. |
| How does horizontal transfer increase variation? | Introduces new genes into a genome, increasing genetic diversity. |
| What is transformation? | Uptake of foreign DNA from the environment by a bacterial cell. |
| What is transduction? | Transfer of bacterial DNA by a bacteriophage (virus). |
| What is conjugation? | Direct transfer of DNA between bacterial cells via a pilus. |
| What is transposition? | Movement of a DNA segment (transposon) from one location to another. |
| How do viruses recombine genetic information? | Through reassortment of viral genomes or recombination during co-infection. |
| What reproductive processes increase genetic variation? | Crossing over, independent assortment, and random fertilization. |
| How is genetic engineering used to analyze DNA? | Techniques like PCR and electrophoresis allow for DNA profiling and sequencing. |
| How is genetic engineering used to manipulate DNA. | Cutting and pasting DNA to create recombinant organisms. |
| What is gel electrophoresis? | Lab technique to separate DNA fragments based on size and charge. |
| What is the function of gel electrophoresis? | To separate DNA fragments for analysis or visualization. |
| What occurs during gel electrophoresis? | DNA fragments migrate through a gel toward the positive pole; smaller fragments move faster. |
| What information can be drawn from a gel electrophoresis? | Fragment sizes, genetic identity, or presence of specific genes. |
| Identify an example of when a gel electrophoresis should be done. | DNA fingerprinting for forensics or paternity testing. |
| What is PCR? | Polymerase Chain Reaction; technique to amplify specific DNA segments. |
| What is the function of PCR? | To make millions of copies of a specific DNA sequence. |
| What occurs during a PCR? | Repeated cycles of heating and cooling with DNA polymerase to replicate DNA. |
| Identify an example of when a PCR should be done. | Amplifying DNA from a crime scene sample. |
| What is bacterial transformation? | Process of introducing foreign DNA into bacterial cells. |
| What is the function of bacterial transformation? | To express recombinant proteins or study gene function. |
| What occurs during a bacterial transformation? | Bacteria take up plasmid DNA containing a gene of interest. |
| What information can be drawn from a bacterial transformation? | Gene function, protein production, or antibiotic resistance. |
| Identify an example of when a bacterial transformation should be done. | Producing human insulin using bacteria. |
| What is DNA sequencing? | Process of determining the precise order of nucleotides in a DNA molecule. |
| What is the function of DNA sequencing? | To read the genetic code for research or medical diagnosis. |
| What occurs during the process of DNA sequencing? | Fluorescently labeled nucleotides are read to determine the sequence. |
| What information can be drawn from DNA sequencing? | Identification of genes, mutations, or genetic relationships. |
| Identify an example of when DNA sequencing should be done. | Diagnosing a genetic disorder. |
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