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AP Bio Unit 6
AP Biology
| Question | Answer |
|---|---|
| Explain why DNA is a good molecule for storing hereditary information. | DNA is suitable for storing hereditary information because it has a stable double helix structure, can replicate accurately through complementary base pairing, and can undergo mutations that create genetic variation. |
| Explain why purines must pair with pyrimidines in DNA. | Purines have two rings, while pyrimidines have one ring. Pairing one purine with one pyrimidine keeps the DNA helix uniform in width. Pairing two purines= bulge, and two pyrimidines =narrow gap, which proofreading enzymes detect and correct. |
| Why does A pair with T and C with G? | Base pairing occurs because of hydrogen bonding patterns. Adenine forms two hydrogen bonds with thymine, while cytosine forms three hydrogen bonds with guanine. Other combinations do not align correctly and would leave unpaired bonds. |
| Explain why DNA replication is semiconservative. | NA replication is semiconservative because each new DNA molecule contains one original parental strand and one newly synthesized strand. The parental strand acts as a template for building the new complementary strand. |
| Explain the difference between the leading and lagging strands | DNA polymerase synthesize DNA in the 5′ → 3′ direction. The leading strand is synthesized continuously toward the replication fork, while the lagging strand is synthesized discontinuously away from the fork in Okazaki fragments |
| Helicase | Unwinds the DNA double helix by breaking hydrogen bonds. |
| Topoisomerase | Relieves twisting tension ahead of the replication fork. |
| DNA Polymerase | Adds nucleotides to the growing DNA strand and proofreads errors. |
| Ligase | Joins Okazaki fragments together. |
| Describe the process of transcription. | During transcription, RNA polymerase binds to a promoter on DNA and synthesizes an mRNA strand using the DNA template strand. The enzyme reads the template strand 3′ → 5′ and builds RNA 5′ → 3′ using complementary base pairing. |
| mRNA | Carries the genetic message from DNA to ribosomes. |
| tRNA | Transfers specific amino acids to the ribosome. |
| rRNA | Forms the structure of the ribosome and helps catalyze protein synthesis. |
| Explain the purpose of the poly-A tail and 5′ cap. | The 5′ cap and poly-A tail protect mRNA from degradation, help it exit the nucleus, and assist ribosomes in recognizing and binding the mRNA for translation. |
| Explain alternative splicing. | Alternative splicing occurs when different combinations of exons are joined together during mRNA processing. This allows a single gene to produce multiple proteins, increasing protein diversity. |
| Initiation | The ribosome binds to the start codon and the first tRNA attaches. |
| Elongation | tRNA molecules bring amino acids to the ribosome, and peptide bonds form. |
| Termination | A stop codon signals the release of the completed protein. |
| Codons | Three-base sequences on mRNA that specify amino acids. |
| Anticodons | Complementary sequences on tRNA that match codons and ensure the correct amino acid is added. |
| Why can transcription and translation occur simultaneously in prokaryotes? | Prokaryotes lack a nucleus, so transcription occurs directly in the cytoplasm. Ribosomes can begin translating mRNA while it is still being transcribed. |
| Why do cells regulate gene expression? | Cells regulate gene expression to conserve energy, respond to environmental changes, and allow cell specialization in multicellular organisms. |
| Explain how transcription factors regulate genes. | Transcription factors are proteins that bind to promoter or regulatory DNA sequences and either activate or inhibit transcription, controlling whether a gene is expressed. |
| Explain how the lac operon works. | The lac operon is a control gene required for lactose metabolism. When lactose is absent, a repressor protein binds preventing transcription. When lactose is present, it binds to the repressor and removes it from the operator, allowing transcription. |
| Explain how mutations affect phenotype. | Mutations alter the DNA sequence, which can change the amino acid sequence of proteins. Changes in protein structure or function may lead to changes in the organism’s phenotype. |
| Explain why mutations can be beneficial, neutral, or harmful. | The effect of a mutation depends on how it affects protein function and the environmental conditions. Some mutations improve survival, some have no effect, and others disrupt important proteins. |
| Explain heterozygote advantage in sickle cell disease. | Individuals heterozygous for the sickle cell allele (AS) have partial resistance to malaria, giving them a survival advantage in regions where malaria is common. Natural selection therefore maintains the sickle cell allele in these populations. |
| Explain how gel electrophoresis separates DNA. | DNA fragments are placed in a gel and exposed to an electric current. Because DNA is negatively charged, it moves toward the positive electrode. Smaller fragments move faster and farther through the gel than larger fragments. |
| Explain how PCR works. | PCR amplifies DNA by repeatedly cycling through heating, cooling, and DNA synthesis, allowing DNA polymerase to create millions of copies of a target DNA sequence. |
| DNA | stores information |
| Replication | copies information |
| Transcription | converts DNA → RNA |
| Translation | converts RNA → protein |
| Gene regulation | controls when proteins are made |
| Mutations | change information |
| Biotechnology | lets humans manipulate information |
Created by:
Leo12345
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