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Ap Bio Mod 35-39
| Question | Answer |
|---|---|
| Operons: | -A group of genes in prokaryotes that be turned on or off depending on environmental conditions. -Ex: Lac operon → genes for lactose metabolism are only expressed when lactose is present. |
| How are Operons controlled? | -Operons are regulated at the promoter/operator region. -Activators: Proteins that help RNA polymerase bind to the promoter → turn the operon on. -Repressors: Proteins that block RNA polymerase → turn the operon off. |
| Operator | A DNA segment in an operon that acts as a “ on/off switch”. -Binding site for repressors (and sometimes activators). -Determines whether RNA polymerase can transcribe the genes in the operon. |
| How can human cells differentiate so many functions even though they all contain the same set of genes? | Gene regulation controls which genes are expressed, producing different proteins and functions in each cell type. |
| Positive Regulation: | -Activator proteins help RNA polymerase bind to the promoter. -Turns genes on or increases transcription. |
| Negative Regulation: | -Repressor proteins block RNA polymerase from binding or moving along DNA. -Turns genes off or decreases transcription. |
| Inducer | -A molecule that activates gene expression in an operon. -Works by binding to a repressor or activator to change its activity. |
| How does transcription regulation differ between Prokaryotes and Eukaryotes | -In Eukaryotic transcription regulation each gene has a promoter -in prokaryotes a single promoter controls a group of genes (operon) |
| siRNA and miRNA | - siRNA (small interfering RNA) and miRNA are RNA regulatory molecules that act as guides and markers for RISC so it can repress translation or cause mRNA degradation -Both are part of RNA interference (RNAi). |
| RNA Interference (RNAi): | A gene-silencing mechanism where small RNAs prevent expression of specific genes. -Uses siRNA or miRNA to target mRNA and RISC to perform repression transcription or mRNA degradation |
| Histone Acetylation: | -Adding acetyl groups to histone proteins. -Loosens DNA-histone interaction → DNA becomes more accessible. -Usually increases transcription (genes turned on). |
| DNA Methylation: | - Adding a methyl groups to DNA (often cytosine bases). -Makes DNA more tightly packed or recruits repressors. -Usually decreases transcription (genes turned off). |
| Epigenetic Modifications: | Chemical changes to DNA or histone proteins that affect gene expression without changing the DNA sequence. - Ex: DNA methylation, Histone acetylation |
| Genomic Imprinting: | -An epigenetic phenomenon where only one allele of a gene is expressed, depending on whether it came from the mother or father. -The other allele is silenced, |
| Stem Cells: | Undifferentiated cells that can differentiate into specialized cell types. -they can divide and make more stem cells like itself |
| Totipotent | Can form all cell types, including embryonic and extraembryonic tissues |
| Pluripotent | Can form all body cell types, but not extraembryonic tissues. |
| Multipotent | Can form multiple related cell types, but within a specific lineage. Example: hematopoietic stem cells → red blood cells, white blood cells, platelets. |
| mutation | a change in a sequence of DNA |
| Inducible Operon | -Usually off, turned on by an inducer. -Genes are expressed only when needed. -Example: lac operon → turned on when lactose is present. |
| Repressible Operon | -Usually on, turned off by a corepressor. -Genes are expressed until the product accumulates. -Example: trp operon → turned off when tryptophan is abundant. |
| Corepressor | A molecule that binds to a repressor protein and activates it. -EX: In the trp operon, tryptophan acts as a corepressor: When tryptophan levels are high, it binds the trp repressor → shuts down transcription of tryptophan-synthesis genes. |
| Ubiquitin | -A small protein that marks other proteins for degradation. -Marks proteins that are damaged, misfolded, or no longer needed. |
| Proteasome: | -A large protein complex that recognizes ubiquitin-tagged proteins. -Breaks them down into small peptides. |
| Dicer | -Cuts long double-stranded RNA into small interfering RNAs (siRNA) or microRNAs (miRNA). -These small RNAs then guide the RNA-induced silencing complex (RISC) to target mRNAs for degradation or translational repression. |
| RISC (RNA-Induced Silencing Complex): | -A protein-RNA complex in RNA interference (RNAi). -Uses the small RNAs (siRNA or miRNA). as guides to find complementary mRNA. -Silences the mRNA by degrading or blocking translation |
| Point Mutation | A change in a single nucleotide. -Ex: Point mutation, Missense mutation, Nonsense mutation |
| Silent Mutation (type of point mutation) | -Changes a codon but does NOT change the amino acid. -Usually no effect on protein function. |
| Missense Mutation (type of point mutation) | -Changes a codon so it codes for a different amino acid. -Can have minor or severe effects on protein function. |
| Nonsense Mutation (type of point mutation) | -Changes a codon to a stop codon. -Causes premature termination of the protein → usually nonfunctional. |
| Frameshift Mutation | -Insertion or deletion of nucleotides not in multiples of 3. -Shifts the reading frame, altering all downstream amino acids. -Usually very damaging. |
| Transposons (Transposable Elements): | -DNA sequences that can move from one location in the genome to another. -Can disrupt genes when they insert into coding or regulatory regions. |
| Spontaneous Mutations | -Occur naturally during DNA replication or repair. -Can result from errors in replication, , or unrepaired DNA damage |
| Induced Mutations | Caused by external factors (mutagens). Examples: Radiation (UV, X-rays) → DNA breaks |
| Horizontal Gene Transfer | -Movement of genes between organisms (not parent → offspring). -important in bacteria for spreading traits like antibiotic resistance. Types: Transformation, Transduction, Conjugation |
| Transformation | Uptake of DNA from the environment into a cell. |
| Transduction | Virus-mediated transfer of DNA between cells. - a virus within one cell infects another cell thus inject DNA from the previous cell into another |
| Conjugation | Direct DNA transfer between cells through a pilus. -bacteria directly transfer genetic information through pili that act as a bridge for sending the genetic information |
| Bacteria structure | -Nucleoid (region where DNA is) -plasmids (small circular DNA) -Cell wall -Capsule -Pili (tiny structures that stick out of bacteria) |
| Morphology | classifying virus by shape -Ex:Helical, Icosahedral,Enveloped |
| 3 types of nutritional bacterial types | Phototrophs- bacteria that get energy from sunlight Lithotrophs- get energy from inorganic compounds -Organotrophs- get energy from organic compounds |
| Heterotrophs and autotrophs (Bacteria) | -heterotrophs=bacteria that get carbon from organic compounds -autotrophs= bacteria that get carbon from carbon fixation |
| 3 theories of viral origin | - cellular theory- the idea that viruses used to be part of cells -regressive theory- the idea that viruses were originally cells that eventually regressed into being parasites -coevolution- the idea that viruses evolved as cells evolved |
| Virus structure | - nucleic acids (RNA or DNA) - caspids (protein coats that surround virus) -envelope (a lipid bilayer with proteins that allows for attachment to cells) -a membrane that is made of the membrane of previously infected cells (eukaryotes only) |
| Viral reproduction (lytic cycle) | -#1 viruses inject their genetic info into a bacteria's cell -#2 as the bacterial cell replicates the viral genetic information replicates too #3 Viral mRNA is made from the viral DNA to make proteins #4 These proteins form new viruses to lyse cell |
| Viral reproduction (lysogenic cycle) | -#1 virus inject their genetic information into hgost and tghat genetic information meges with the hosts cell's DNA #2 everythime the host does DNA replication the viral DNA replicates as well |
| Prophage | -what a virus becomes when it inserts its DNA into bacteria |
| PCR (Polymerase Chain Reaction) | - a laboratory technique used to amplify (make millions of copies of) a specific DNA sequence in a short amount of time. |
| 3 steps of PCR (Polymerase Chain Reaction) | Denaturation (very hot temperature) – DNA strands separate. Annealing (cool temperature) – Oligonucleotides: Primers bind to the target sequence. Extension (hot temperature) – DNA polymerase synthesizes new DNA strands based on Oligonucleotides |
| Taq polymerase | -The special DNA polymerase used in PCR -Synthesizes new DNA during the extension step. -Doesn’t denature at the high denaturation temperature so it can survive repeated PCR cycles. |
| Gel Electrophoresis: | -A laboratory technique used to separate DNA, RNA, or proteins based on size and charge. |
| DNA Ladder (in Gel Electrophoresis): | -A mixture of DNA fragments of known sizes. -Purpose: Acts as a molecular ruler to estimate the size of unknown DNA fragments in the gel. -Run alongside samples in the gel for comparison. |
| Explain how Gel Electrophoresis works | -Molecules are placed in a gel and an electric current is applied. -Negatively charged molecules moves toward the positive electrode and vice versa -used to compare molecule sizes, detect mutations, or prepare samples for cloning. |
| Sanger Sequencing: | A DNA sequencing method that uses dideoxynucleotides (ddNTPs) to terminate DNA synthesis at specific bases. -Produces DNA fragments of different lengths, each ending at a ddNTP. -Fragments are separated by size using gel electrophoresis. |
| DNA Sequencing: | The process of determining the exact order of nucleotides (A, T, C, G) in DNA. -Reveals the genetic code of a gene, chromosome, or genome. thus allowing for comparisons between different genomes to check for mutations and other abnormalties |
| Sticky Ends: | DNA fragments with single-stranded overhangs created by some restriction enzymes. |
| Restriction Enzyme | -Proteins that cut DNA at specific sequences called restriction sites. -Produce either: Sticky ends (overhanging single-stranded DNA) Blunt ends (straight cut across both strands) |
| CRISPR | A gene-editing tool that allows scientists to precisely modify DNA in cells. Works with Cas9 protein, which acts as molecular scissors to cut DNA at a specific sequence -After the cut, the cell’s DNA repair machinery can insert new DNA. |
| Recombinant DNA Technology: | -A set of techniques used to combine DNA from different sources into a single DNA molecule -Cutting DNA with restriction enzymes -Joining fragments using DNA ligase -Inserting recombinant DNA into host organisms for replication or expression |
| Why aren't Viruses considered living organisms | -No metabolism -Require a host: -cannot grow on their own |
| Difference between pathogenicity and virulence | - pathogenicity=The ability of a microorganism to cause disease. - Virulence= The degree or severity of disease a pathogen causes. |
| Role of Viruses in Ocean Photosynthesis: | - when viruses lyse phytoplankton, thus releasing nutrients back into the water that other phytoplankton can then use to do photosynthesis |
| Oligonucleotides: | -Short DNA or RNA sequences -Used as primers in PCR |
| Vector (in Genetic Engineering): | -A DNA molecule used to carry foreign DNA into a host cell. Common types: Plasmids → circular DNA in bacteria Viruses → can deliver genes to eukaryotic cells |
| Bacteriophage | A virus that infects bacteria. |
| DNA Bending Proteins: | -Proteins that bind to DNA and physically bend it. -allows activators that are far away to come in contact the promoter to initiate transcription |
Created by:
KenechukwuIE