Oral Exam 2 Study Guide PDF
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Carthage College
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Summary
This study guide covers several topics in biology, including horizontal gene transfer, mutations, and gene regulation. It details different types of mutations and their potential impact, along with the mechanisms that cells use to prevent or repair mutations.
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Study guide 1. What is horizontal gene transfer? Can all organisms undergo horizontal gene transfer? What are some potential benefits and risks of this process? Horizontal gene transfer (HGT): when genetic material is transferred between different organisms, not passed down from parent to of...
Study guide 1. What is horizontal gene transfer? Can all organisms undergo horizontal gene transfer? What are some potential benefits and risks of this process? Horizontal gene transfer (HGT): when genetic material is transferred between different organisms, not passed down from parent to offspring. Example: Conjugation: ○ the process where one bacterium directly transfers genetic material (usually in the form of a plasmid) to another bacterium through physical contact, with the donor cell using a structure called a pilus to establish the connection and transfer the DNA to the recipient cell Organisms that undergo HGT: Primarily observed in bacteria and some other prokaryotes, though evidence shows it can happen in some eukaryotes. Benefits: ○ Increases genetic diversity. ○ Can confer advantages, such as antibiotic resistance in bacteria. Risks: ○ May spread harmful traits (e.g., pathogenicity or drug resistance). ○ Could disrupt local ecosystems by introducing foreign genes. 2. How do mutations occur? Describe some different types of mutations and their potential impact. Mutation: A mutation is a change in the DNA sequence, which can arise spontaneously or due to environmental factors. Types of mutations: ○ Point mutations: A single nucleotide change (e.g., missense, nonsense, silent) -Nonsense mutation: mutation where a codon is changed into a stop codon -Impact: end termination of translation prematurely and can produce nonfunctional proteins that can lead to disease like cystic fibrosis ○ Insertions/Deletions (Indels): Adding or removing bases -Impact: possibly causing frameshift. ○ Chromosomal mutations: Large-scale changes, such as duplications, inversions, or translocations. Impact of mutations: Can range from benign to beneficial or harmful. Some mutations lead to genetic disorders, while others can confer an evolutionary advantage. Beneficial mutation: resistance to infectious diseases ○ Genetic variants that improve metabolic efficiency or physical resilience Harmful mutation: cystic fibrosis ○ Mutation in a single gene causes the body to produce thick, sticky mucus that clogs the lungs and blocks ducts in digestive organs 3. How do cells prevent mutations? Why do cells both attempt to prevent errors in DNA replication and use DNA repair systems? DNA proofreading: DNA polymerases check and correct errors during DNA replication. Mismatch repair: Detects and repairs errors post-replication. Importance of DNA repair systems: While proofreading prevents many mutations, repair systems are necessary to fix errors or damage that occur despite prevention, maintaining genome stability. 4. Differences in chromosome structure and organization between bacteria and eukaryotes Bacterial chromosomes: ○ Typically circular, single chromosome. ○ DNA lacks histones and forms a nucleoid region. Eukaryotic chromosomes: ○ Linear chromosomes within a nucleus. ○ DNA wrapped around histones, forming chromatin. 5. How transcription and translation relate to gene expression and traits Transcription: DNA is transcribed to mRNA. Translation: mRNA is translated into proteins, which perform cellular functions and contribute to phenotypic traits. Gene expression: Proteins produced from genes directly influence an organism’s traits. 6. What is a repressor and an activator? How do these proteins regulate gene expression in bacteria and eukaryotes? Repressor: A protein that binds to DNA and inhibits transcription. activator: A protein that binds to DNA and increases transcription. Gene regulation: ○ In bacteria: repressors and activators directly interact with operons. - -Repressors: - Bind to operator regions on the DNA. - Block RNA polymerase from transcribing the gene. - Example: The lac operon uses a repressor to prevent lactose metabolism genes from being expressed in the absence of lactose. -Activators: -Bind to promoter regions or nearby sites, enhancing RNA polymerase binding and activity. -Example: The CAP protein activates transcription of the lac operon when glucose is scarce and lactose is present. ○ In eukaryotes: they control transcription through more complex interactions with transcription factors and enhancer/silencer regions. ○ Repressors: Bind to silencer regions or interact with other proteins to inhibit transcription. May recruit proteins that condense chromatin, making DNA inaccessible to transcription machinery. Example: Repressors of the p53 gene can suppress tumor-suppressor activity, potentially leading to uncontrolled cell growth. ○ Activators: Bind to enhancer regions and recruit transcription factors or RNA polymerase. Can modify chromatin to expose DNA for transcription. Example: Activators like the Sp1 transcription factor promote gene expression by stabilizing RNA polymerase binding. 7. Purpose of PCR and gel electrophoresis. Why are these useful laboratory techniques? PCR (Polymerase Chain Reaction): Amplifies specific DNA sequences, useful for research, diagnostics, and forensic analysis. Gel electrophoresis: Separates DNA fragments by size, allowing visualization of PCR products or genetic differences. Uses: Both techniques are essential for analyzing and manipulating DNA in various biological studies. 8. At what stages of the central dogma is gene expression regulated? Why do cells undergo regulation of gene expression at various stages? Stages: ○ Transcriptional (controlling mRNA production). ○ Post-transcriptional (mRNA processing). ○ Translational (controlling protein synthesis). ○ Post-translational (modifying proteins after synthesis). Why regulate at various stages: Allows cells to respond precisely to environmental signals and control protein production based on need. 9. What is a non-coding RNA (ncRNA)? Describe some of the functions of non-coding RNAs. Non-coding RNA: RNA molecules that do not code for proteins but have various roles. Functions: ○ rRNA and tRNA: Essential for protein synthesis. ○ miRNA and siRNA: Involved in gene silencing and regulation. ○ lncRNA: Involved in chromatin remodeling and transcriptional regulation. 10. What is DNA sequencing? Why is DNA sequencing an important technological advance? DNA sequencing: The process of determining the precise order of nucleotides in a DNA molecule. Importance: ○ Facilitates understanding of genetic makeup. ○ Critical in medicine for diagnosing genetic disorders, in evolution studies, and in developing targeted therapies.