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Ap Bio Mod 31-34
| Question | Answer |
|---|---|
| how do nucleic acids store and carry information? | -Nucleic acids store and carry information through the sequence of their nitrogen bases. -In DNA, the order of bases (A, T, C, G) stores genetic instructions. |
| Explain the differences between DNA and RNA? | - DNA has deoxyribose sugar , RNA has Ribose sugar -DNA is double strand, RNA is mostly single stranded -DNA has a hydrogen (H) on its sugar, RNA has a OH (hydroxyl) on its sugar |
| Purines | -Adenine (A) and Guanine (G) - they have double-ring structure - Remember "Pure as Gold" |
| Pyrimidines | Cytosine (C), Thymine (T in DNA), and Uracil (U in RNA). - Pyrimidines "Perfect The Craft and Urself" |
| How many hydrogen bonds between Adenine (A) and Thymine (T) | 2 hydrogen bonds |
| How many hydrogen bonds between Guanine (G) and Cytosine (C) | 3 hydrogen bonds |
| Transcription: | The process of copying a gene’s DNA sequence into mRNA. - occurs in Nucleus for Eukaryotes and in the cytoplasm with Prokaryotes |
| Translation: | The process where ribosomes read mRNA and assemble amino acids into a protein. -occurs in the cytoplasm for Eukaryotes and Prokaryotes |
| Describe the Central Dogma pathway | DNA-> RNA (Transcription) , RNA-> Protein (Translation) |
| Gene | a segment of DNA that codes for a particular protein |
| Gene regulation | the process of controlling the level of gene expression done or the timing that gene expression occurs -Ex: DNA methylation, RNAI, Transcription factors |
| Why is gene regulation needed for organisms? | -Allows cell specialization (ex: muscle vs. nerve cells) as keeping some genes on and others off is what makes cells distinct -Helps organisms respond to environmental changes -Saves energy and resources by not making unnecessary proteins |
| Non coding RNA | RNA molecules that are not translated into proteins but have functional roles in the cell. -Examples: rRNA, tRNA, miRNA |
| How the nucleus changes the central dogma: | -Prokaryotes (no nucleus)- Transcription and translation happen at the same time in the cytoplasm. - Eukaryotes (have nucleus)- Transcription and translation occur at different locations and time |
| Plasmid | A small, circular piece of DNA found in bacteria that is separate from the main chromosome and can replicate independently. --Can be transferred between bacteria. -Often carries extra genes, like antibiotic resistance. |
| Chromosome Scaffold Model (Eukaryotes | DNA is wrapped around histone proteins (forming chromatin) and attached to a protein scaffold that helps organize and condense chromosomes inside the nucleus. |
| Nucleoid Model (Prokaryotes): | DNA is located in a nucleoid region (not membrane-bound). It is coiled and looped but not enclosed in a nucleus. |
| Antiparallel DNA | The two strands of DNA run in opposite directions: -One strand runs 5’ → 3’ -The other runs 3’ → 5’ |
| Replication Fork: | The Y-shaped region where DNA is unwound so each strand can be copied during DNA replication -Formed by helicase unwinding the double helix. |
| Leading Strand: | DNA strand that is copied continuously in the same direction as the replication fork. |
| Lagging Strand | -DNA strand that is copied in short fragments (Okazaki fragments -grows in the opposite the replication fork direction. -Fragments are later joined by DNA ligase. |
| Helicase | Unwinds and separates the DNA double helix at the replication fork. - used for DNA replication |
| Topoisomerase | Relieves twisting tension in DNA ahead of the replication fork. - used for DNA replication |
| DNA Polymerase III | Adds new nucleotides to the growing DNA strand (main enzyme for elongation). -used for DNA replication |
| Rna primase | -Enzyme that synthesizes a short RNA primer on the DNA template to give DNA polymerase a starting point for replication.- used for DNA replication |
| Primer | Short RNA segment that provides a starting point for DNA polymerase. - used for DNA replication |
| Telomeres | Repeating DNA sequences at the ends of eukaryotic chromosomes that protect them from damage. - |
| Telomerase: | Enzyme that adds DNA to telomeres, preventing chromosome shortening. |
| DNA Polymerase I | Removes RNA primers and replaces them with DNA. |
| DNA Ligase | Enzyme that joins Okazaki fragments on the lagging strand |
| Single-Strand Binding Proteins (SSBs) | -Enzymes that bind to unwound DNA strands to keep them separated during replication. -Prevents the strands from reforming a double helix or getting damaged. |
| DNA Proofreading: | -DNA polymerases check each new nucleotide as it is added. -If a wrong base is added, the enzyme removes it and replaces it with the correct one. |
| Template Strand | - The DNA strand that is read by RNA polymerase to make mRNA. Runs 3’ → 5’, so mRNA is made 5’ → 3’. - has a Complementary sequence to mRNA |
| Non-Template (Coding) Strand: | -The DNA strand not used as a template. for mRNA synthesis -Its sequence is the same as the mRNA (except T in DNA is U in RNA). -Runs 5’ → 3’. |
| Pre-mRNA: | The initial RNA transcript made from DNA during transcription. Contains both introns (non-coding) and exons (coding). Must be processed (splicing, 5’ cap, poly-A tail) to become mature mRNA |
| Mature RNA | The processed form of RNA that is ready to leave the nucleus and be used in translation. -has 5’ cap added, Poly-A tail added, Introns removed (splicing) |
| Initiation (Transcription) | RNA polymerase binds promoter, DNA is unwinded , RNA synthesis begins |
| Elongation (Transcription) | RNA polymerase adds nucleotides complementary to the DNA template strand. |
| Termination (Transcription) | RNA polymerase reaches terminator sequence and releases RNA |
| Promoters | the sequences of DNA where RNA polymerase binds to the DNA molecule to initiate transcription - |
| Transcription Factors: | Proteins that help RNA polymerase bind to DNA and start transcription. -They recognize and bind to promoter regions of genes to allow RNA polymerase to bind and do transcription -Act as activators or repressors to turn genes on or off. |
| Transcription Initiation Complex: | A protein-DNA assembly that starts transcription in eukaryotes. Includes: Promoter DNA, , Transcription factors , and RNA polymerase II -formed in order to start transcription |
| mRNA (messenger RNA): | -Carries the genetic code from DNA to the ribosome. -Template for protein synthesis. |
| tRNA (transfer RNA) | -Brings specific amino acids to the ribosome. -Matches anticodon to mRNA codon during translation. |
| rRNA (ribosomal RNA): | -structural unit that makes up ribosomes. -Catalyzes peptide bond formation and guides translation. |
| Four Main functions of RNA Polymerase | -Binds to Promoter to start transcription. -Unwinds DNA -Synthesizes RNA: Terminates Transcription: Stops RNA synthesis at terminator sequence and releases the RNA. |
| GTP Cap (5’ Cap): | -Added to the 5’ end of pre-mRNA. -Protects mRNA from degradation as it travels to ribosome |
| Poly-A Tail: | -Added to the 3’ end of pre-mRNA (a string of adenine nucleotides). -Protects mRNA from degradation as it travels to ribosome |
| Exons | Coding sequences in RNA that remain on mature mRNA and are translated into protein. |
| Introns | Non-coding sequences in RNA that are removed during processing -they remain in the nucleus |
| RNA Splicing | The process of removing introns and joining exons to make mature mRNA. |
| Alternative Splicing: | -Different exons can be included or skipped depending on the cell -Multiple proteins can be made from a single gene. |
| Nucleosomes | The basic unit of DNA packaging in eukaryotes -DNA is wrapped around histone proteins -Helps condense DNA so it fits in the nucleus. |
| Semiconservative Model of DNA Replication: | Each new DNA molecule consists of one original (parent) strand and one newly made strand. |
| Spliceosomes | -RNA-protein complexes in eukaryotic cells. -Carry out RNA splicing by removing introns from pre-mRNA and joining exons. |
| UTR (Untranslated Region): | -binding sites for small regulatory proteins to control RNA translation (Control elements) -Located on mRNA -Affect mRNA stability (how long mRNA lasts until it is degraded) |
| Do Prokaryotes do RNA processing? | NO! -They don't do any form of RNA processing such as alternative splicing, 5’ capping, poly-A tails, or introns and exons - |
| Three sites of Translation | -A site (Aminoacyl site): -P site (Peptide site) -E site (exit) site |
| A site (Aminoacyl site): | Where tRNA carrying a new amino acid enters and pairs with the mRNA codon. |
| P site (Peptidyl site): | -Holds the tRNA with the growing polypeptide chain. -Peptide bonds form here between amino acids. |
| E site (Exit site) | -Where empty tRNA exits the ribosome after transferring its amino acid. |
| Translocation | The movement of the ribosome along the mRNA by one codon during translation. Shifts tRNAs: tRNA in A site → P site, tRNA in P site → E site (then exits) -Allows the next codon to be read and the polypeptide to grow. |
| Codon | A sequence of three nucleotides on mRNA that codes for one amino acid. -Example: AUG , codes for methionine (Amino acid) |
| Reading Frame | The correct grouping of nucleotides into codons. -Ribosomes follow the reading frame to read codons properly. -Correct reading frame ensures the protein is built accurately. |
| Anticodon | A sequence of three nucleotides on tRNA that is complementary to an mRNA codon. -tRNA with the correct anticodon pairs with its matching mRNA codon in the ribosome’s A site. -The tRNA carries a specific amino acid corresponding to the codon. |
| Why is the genetic code considered redundant? | because many codons can code for the same amino acid |
| Start and Stop codons? | Start Codon:AUG → codes for amino acid (methionine) -Signals where translation begins. - Stop Codons there are multiple→ do not code for any amino acid. -Signal where translation ends, releasing the polypeptide. |
| Initiation (Translation) | -Ribosome assembles at start codon (AUG) on mRNA. -tRNA carrying methionine binds to the start codon in the P site. |
| Elongation (Translation) | Ribosome moves along mRNA codon by codon. tRNAs bring amino acids to the A site, peptide bonds form, and polypeptide grows. tRNAs shift through A site → P site → E site |
| Termination (Translation) | -Ribosome reaches a stop codon -Release factors prompt ribosome to release the polypeptide. -Ribosome disassembles. |
| Initiation (Replication) | Helicase unwinds DNA, creating replication forks. Primase lays down RNA primers for DNA polymerase. |
| Elongation (Replication) | -DNA Polymerase III adds nucleotides to the 3’ end of the new strand. -Leading strand is copied continuously; lagging strand in Okazaki fragments. -SSBs keep strands separated; topoisomerase relieves tension. |
| Termination (Replication) | -DNA polymerase reaches the end of the template (or another fork). -DNA Polymerase I replaces RNA primers with DNA. -DNA ligase joins Okazaki fragments |
| Heterochromatin | - tightly packed DNA that is thus unaviable for transcription |
| Euchromatin | - loosely packed DNA that is thus available for transcription |
| Ubiquitin | -A small protein that tags other proteins for degradation. -Marks proteins that are damaged, misfolded, or no longer needed. -post translational control |
| Proteasome | -A large protein complex that recognizes ubiquitin-tagged proteins. -Breaks them down into small peptides. -Post transcriptional regulation |
| Dicer | An RNA interference enzyme -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): | -Uses small RNAs (siRNA or miRNA). as a guide to find mRNA. -Silences the mRNA by degrading it or block its translation |
| Point Mutation | A change in a single nucleotide. Ex:Silent 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. - |
| 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. |
Created by:
KenechukwuIE