Unit 4 Honors Study Guide: Protein Synthesis & Mutations PDF
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Summary
This study guide covers key topics in molecular biology, including DNA structure and replication, protein synthesis (transcription and translation), gene expression, and various types of mutations. The guide also includes definitions and examples for each topic.
Full Transcript
Unit 4 HONORS Study Guide: Protein Synthesis & Mutations DNA Structure & Replication DNA Structure ○ N ucleotide: Composed of a sugar (deoxyribose), a phosphategroup, and a nitrogenous base (A, T, C, G). ○ Chargaff's Rule: A = T an...
Unit 4 HONORS Study Guide: Protein Synthesis & Mutations DNA Structure & Replication DNA Structure ○ N ucleotide: Composed of a sugar (deoxyribose), a phosphategroup, and a nitrogenous base (A, T, C, G). ○ Chargaff's Rule: A = T and C = G (complementary basepairing). ○ Antiparallel: The two strands of DNA run in oppositedirections (5' to 3' vs 3' to 5'). ○ Contributions of Scientists: Watson and Crick: Discovery of the double-helix structure. Rosalind Franklin: X-ray diffraction images contributing to the structure. Erwin Chargaff: Base pairing rules (A = T, C = G). D NA Replication ○ Enzymes Involved: Helicase: Unwinds the DNA helix. DNA Polymerase: Adds complementary nucleotides tothe growing strand. Ligase: Seals the gaps between the Okazaki fragments. Primase: Creates RNA primers to start replication. ○ Leading Strand: Continuously synthesized in the 5'to 3' direction. ○ Lagging Strand: Discontinuously synthesized in fragments(Okazaki fragments). ○ Okazaki Fragments: Short segments of DNA synthesizedon the lagging strand. Protein Synthesis Transcription W ○ here: Occurs in the nucleus (in eukaryotes). ○ Process: RNA Polymerasebinds to DNA at the promoter region. RNA polymerase creates an mRNA strand using the DNA template. mRNAis synthesized from 5' to 3'. RNA Processing: In eukaryotes, the mRNA is spliced,adding a cap and tail. Translation W ○ here: Occurs in the ribosome (in the cytoplasm). ○ Process: m RNAis read in sets of three bases (codons). tRNAbrings the corresponding amino acids to the ribosome. The ribosome forms peptide bonds between amino acids to form a polypeptide chain. ○ Codon Chart/Wheel: Use the codon chart to match mRNAcodons to amino acids. START Codon: AUG, signals the beginning of translation. ○ ○ STOP Codons: UAA, UAG, UGA, signal the end of translation. Gene Expression Importance: Gene expression regulation is vital forcontrolling which proteins are made, when, and in what amounts. Transcription Factors P ○ ositive Transcription Factors: Activate or enhancegene expression. ○ Negative Transcription Factors: Repress gene expression. ○ Binding Sites: Transcription factors bind to specificregions on the promoter of a gene to regulate its transcription. Interfering RNA ○ Types: miRNA (microRNA)andsiRNA (small interfering RNA). ○ Function: They regulate gene expression by bindingto mRNA and preventing translation or promoting mRNA degradation. O perons D ○ efinition: A group of genes regulated together undera single promoter. ○ Lac Operon: Example of an operon in bacteria, regulatedby the presence or absence of lactose. E pigenetics ○ D efinition: Study of changes in gene expression notcaused by changes in DNA sequence. ○ Examples of Epigenetic Markers: DNA Methylation: The addition of methyl groups toDNA, typically represses gene expression. Histone Modification: Histone proteins can be modifiedto either condense or relax chromatin, affecting gene accessibility. Variation Mutations ○ F rameshift Mutations: Caused by insertions or deletions,which shift the reading frame of the codons, leading to a completely different protein. ○ Point Mutations: Changes in a single nucleotide base. Substitution: One base is replaced by another (mayor may not change the protein). Silent Mutation: No change in the protein sequence. Missense Mutation: Changes one amino acid in the proteinsequence. Nonsense Mutation: Changes a codon to a stop codon,leading to a truncated protein. ○ Impact on Fitness: Mutations can cause variationsthat are either beneficial, harmful, or neutral for an individual’s survival and reproduction. ○ Chromosomal Mutations: Deletions: Part of a chromosome is lost. Duplications: Part of a chromosome is repeated. Inversions: Part of a chromosome is reversed. Translocations: Parts of chromosomes are swapped. M utations and Population Variation ○ M utations contribute to genetic diversity within a population, which can lead to natural selection (positive, negative, or neutral effects). Root Words ro-: Before, in front of. P Poly-: Many, multiple. Hist-: Tissue. Anti-: Against. Mut-: Change, alter. Non-: Not. Mis-: Wrong, incorrect. Sub-: Under, below. Trans-: Across, beyond. -scribe, -script: Write, record. Ex-: Out, away from. -gen, -gene: Produce, create, origin.
