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Unit 5 Test Review
Ch. 16, 17, & 18
| Term | Definition |
|---|---|
| Frederick Griffith: | revealed the "transforming principle" which lead to the discovery that DNA acts as the carrier of genetic information |
| Avery, McCarty, & McLeod: | discovered that DNA is the substance that causes bacterial transformation |
| Hershey & Chase: | served to prove that DNA is the hereditary material |
| Bacteriophages: | virus that infects bacteria; composed of DNA & protein |
| Edwin Chargaff: | DNA composition varies between species & paved the way for the discoveries of DNA & its method of replication |
| Rosalind Franklin: | discovered two types of DNA - A-DNA & B-DNA |
| James Watson & Francis Crick: | discovered the double-helix by building models to conform to Franklins x-ray data & Chargaff's Rules |
| "backbone" of DNA is composed of | sugar + phosphate |
| "rungs" of DNA are composed of | nitrogenous bases |
| Nitrogenous Bases: | Adenine (A) Guanine (G) Thymine (T) Cytosine (C) |
| Purine: | Adenine & Guanine |
| Pyrimidine: | Thymine & Cytosine |
| holds molecules together like a zipper: | hydrogen bonds between base pairs of the two strands |
| Antiparallel: | one strand (5’ -> 3’), other strand runs in opposite, upside-down direction (3’ -> 5’) |
| Prokaryotic DNA is: | circular, has one chromosome, is in cytoplasm, has no histones, & has supercoiled DNA |
| Eukaryotic DNA is: | linear, usually has 1+ chromosomes, is in the nucleus, DNA wrapped around histones (proteins), & forms chromatin |
| Replication: | making DNA from existing DNA - is semiconservative |
| Semiconservative: | daughter DNA molecules, each consisting of one parental strand & one new strand |
| Helicase: | unwinds DNA at origins of replication & creates replication forks |
| Topoisomerase: | relieves overwinding strain ahead of replication forks by breaking, swiveling, rejoining DNA strands |
| Primase: | puts down RNA primer to start replication |
| DNA polymerase III: | adds complimentary bases to leading strand (new DNA is made 5’ -> 3’) |
| Lagging Strand: | grows in 3' -> 5’ direction by the addition of Okazaki fragments |
| DNA polymerase I: | replaces RNA primers with DNA |
| DNA ligase: | seals fragments together |
| Okazaki Fragments: | short segments of DNA that grow 5’ -> 3’ that are added onto the Lagging Strand |
| Mismatch repair: | special enzymes fix incorrect pairings |
| Nucleotide excision repair: | - Nucleases cut damaged DNA - DNA poly and ligase fill in gaps |
| Telomeres: | repeated units of short nucleotide sequences (TTAGGG) at ends of DNA - “cap” ends of DNA to postpone erosion of genes at ends (TTAGGG) |
| Telomerase: | enzyme that adds to telomeres |
| Gene Expression: | process by which DNA directs the synthesis of proteins (or RNAs) |
| Function of a gene | dictate production of specific enzyme |
| Flow of genetic material - Central Dogma: | DNA -> RNA -> protein |
| Transcription: | DNA -> RNA |
| Translation: | RNA -> protein - ribosome is the site of translation |
| DNA: | - Nucleic acid composed of nucleotides - Double-stranded - Deoxyribose=sugar - Thymine - Template for individual |
| RNA: | - Nucleic acid composed of nucleotides - Single-stranded - Ribose=sugar - Uracil - Many different roles |
| pre-mRNA: | precursor to mRNA, newly transcribed and not edited |
| mRNA: | edited version; carries the code from DNA that specifies amino acids |
| tRNA: | carries a specific amino acid to ribosome based on its anticodon to mRNA codon - transcribed in the nucleus |
| rRNA: | makes up 60% of the ribosome; site of protein synthesis |
| snRNA: | small nuclear RNA; part of a spliceosome; structural and catalytic roles |
| srpRNA: | signal recognition particle that binds to signal peptides |
| RNAi: | interference RNA; a regulatory molecule |
| miRNA/siRNA: | micro/small interfering RNA; binds to mRNA or DNA to block it, regulate gene expression, or cut it up |
| ribozyme: | RNA that functions as an enzyme |
| template strand | for each gene, one DNA strand is the template strand |
| Codons: | mRNA triplets that code for amino acids in polypeptide chain |
| The Genetic Code is... | - universal; all life forms use the same code - 64 different codon combinations |
| Transcription unit: | stretch of DNA that codes for a polypeptide or RNA - eg. tRNA, rRNA |
| RNA polymerase: | separates DNA strands and transcribes mRNA - uracil (U) replaces thymine (T) when pairing to adenine (A) - attaches to promoter (start of gene) and stops at terminator (end of gene) |
| Transcription: 1. Initiation: Bacteria | RNA polymerase binds directly to promoter in DNA |
| Transcription: 1. Initiation: Eukaryotes | TATA box = DNA sequence (TATAAAA) in promoter region upstream from transcription start site |
| Transcription factors must... | recognize TATA box before RNA polymerase can bind to DNA promoter |
| Transcription Initiation Complex: | Transcription Factors + RNA Polymerase - activators bind to enhancer regions + other proteins + RNA polymerase |
| Transcription: 2. Elongation: | - RNA polymerase adds RNA nucleotides to the 3’ end of the growing chain (A-U, G-C) - As RNA polymerase moves, it untwists DNA, then rewinds it after mRNA is made |
| Transcription: 3. Termination: | - RNA polymerase transcribes a terminator sequence in DNA, then mRNA and polymerase detach (now called pre-mRNA for eukaryotes - mRNA is ready for use in prokaryotes) |
| 5’ cap | modified guanine |
| 3’ poly-A tail | a long chain of adenine nucleotides that is added to the 3’ end of an mRNA molecule during RNA processing |
| Introns: | noncoding sequences |
| Exons: | codes for amino acids |
| Splicing: | introns cut out, exons joined together |
| snRNPs: | small nuclear ribonucleoproteins - snRNP = snRNA + protein - snRNPs join with other proteins to form a spliceosome |
| Spliceosomes: | catalyze the process of removing introns and joining exons |
| Alternative RNA Splicing: | produce different combinations of exons - One gene can make more than one polypeptide - 20,000 genes -> 100,000 polypeptides |
| Anticodon: | pairs with complementary mRNA codon - carried by tRNA |
| wobble: | base-pairing rules between 3rd base of codon & anticodon are not as strict |
| Aminoacyl-tRNA-synthetase: | enzyme that binds tRNA to specific amino acid |
| Ribosomes: | - Ribosome = rRNA + proteins - made in nucleolus - 2 subunits |
| A site: | holds AA to be added |
| P site: | holds growing polypeptide chain |
| E site: | exit site for tRNA |
| Translation: 1. Initiation: | - small subunit binds to start codon (AUG) on mRNA - tRNA carrying Met attaches to P site - large subunit attaches |
| Translation: 2. Elongation: | tRNA anticodon matches codon in A site -> AA in A site forms bond with peptide in P site -> tRNA in A site moves to P site; tRNA in P site moves to E site (then exits) |
| Codon recognition: | tRNA anticodon matches codon in A site |
| Peptide bond formation: | AA in A site forms bond with peptide in P site |
| Translocation: | tRNA in A site moves to P site; tRNA in P site moves to E site (then exits) |
| Translation: 3. Termination: | stop codon reached and translation stops -> Release factor binds to stop codon; polypeptide is released -> Ribosomal subunits dissociate |
| Polyribosomes: | a single mRNA can be translated by several ribosomes at the same time |
| Protein folding: | during synthesis, polypeptide chain coils and folds spontaneously |
| Chaperonin: | protein that helps polypeptide fold correctly |
| Free ribosomes: | synthesize proteins that stay in cytosol and function there |
| Bound ribosomes (to ER): | make proteins of endomembrane system (nuclear envelope, ER, Golgi, lysosomes, vacuoles, plasma membrane) & proteins for secretion - uses signal peptide to target location |
| Signal peptide: | 20 AA at leading end of polypeptide determines destination |
| Signal-recognition particle (SRP): | brings ribosome to ER |
| Mutations: | changes in the genetic material of a cell |
| Large scale mutations: | chromosomal; always cause disorders or death |
| Point mutations: | alter 1 base pair of a gene |
| 1. Base-pair substitutions: | replace 1 with another - Missense: different amino acid - Nonsense: stop codon, not amino acid |
| 2. Frameshift: | mRNA read incorrectly; nonfunctional proteins - caused by insertions or deletions |
| Protein Synthesis - Prokaryotes: | - Transcription and translation both in cytoplasm - DNA/RNA in cytoplasm - RNA poly binds directly to promoter - Transcription makes mRNA (not processed) - No introns |
| Protein synthesis - Eukaryotes: | - Transcription in nucleus; translation in cytoplasm - DNA in nucleus, RNA travels in/out nucleus - RNA poly binds to TATA box & transcription factors - Transcription makes pre-mRNA -> RNA processing -> final mRNA - Exons, introns (cut out) |
| Most current definition for a gene: | a region of DNA whose final product is either a polypeptide or an RNA molecule |
| Operon: | cluster of related genes with on/off switch |
| Three parts of Operon: | 1. Promoter – where RNA polymerase attaches 2. Operator – “on/off”, controls access of RNA poly 3. Genes – code for related enzymes in a pathway |
| Regulatory gene: | produces repressor protein that binds to operator to block RNA polymerase |
| Repressible Operon | organic molecule product acts as corepressor -> binds to repressor to activate it - on -> off - anabolic (build organic molecules) - trp operon |
| Inducible Operon | repressor is active -> inducer binds to and inactivates repressor - off -> on - catabolic (break down food for energy) - lac operon |
| Gene Regulation - Negative Control: | operons are switched off by active form of repressor protein - trp operon, lac operon |
| Gene Regulation - Positive Control: | regulatory protein interacts directly with genome to increase transcription - cAMP & CAP |
| cAMP: | accumulates when glucose is scarce - binds to CAP - active CAP -> binds to DNA upstream of promoter, ↑ affinity of RNA polymerase to promoter, ↑ transcription |
| Differential gene expression | differences between cell types |
| Chromatin Structure: | tightly bound DNA -> less accessible for transcription |
| DNA methylation: | methyl groups added to DNA; tightly packed; decreased transcription |
| Histone acetylation: | acetyl groups added to histones; loosened; increased transcription |
| Epigenetic Inheritance: | - modifications on chromatin can be passed on to future generations - unlike DNA mutations, these changes to chromatin can be reversed (de-methylation of DNA) - explains differences between identical twins |
| Transcription Initiation: | specific transcription factors (activators or repressors) bind to control elements (enhancer region) |
| Activators: | increase transcription |
| Repressors: | decrease transcription |
| Regulation of mRNA: | micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation |
| Embryonic Development - Zygote -> Organism: | 1. Cell Division: large # identical cells through mitosis 2. Cell Differentiation: cells become specialized in structure & function 3. Morphogenesis: “creation of form” –organism’s shape |
| Determination: | irreversible series of events that lead to cell differentiation |
| Cytoplasmic determinants: | maternal substances in egg distributed unevenly in early cells of embryo |
| Induction: | cells triggered to differentiate |
| Cell-Cell Signals: | molecules produced by one cell influences neighboring cells |
| Pattern formation: | setting up the body plan (head, tail, L/R, back, front) |
| Morphogens: | substances that establish an embryo's axes |
| Homeotic Genes: | master control genes that control pattern formation |
| Role of Apoptosis: | - most of the embryonic cells are produced in excess - cells will undergo apoptosis (programmed cell death) to sculpture organs and tissues - carried out by caspase proteins |
| Control of cell cycle: | 1. Proto-oncogene = stimulates cell division 2. Tumor-suppressor gene = inhibits cell division - mutations in these genes can lead to cancer |
| Proto-Oncogene: | gene that stimulates normal cell growth & division |
| Oncogene: | - mutation in proto-oncogene - cancer-causing gene |
| Effects of Oncogene: | - increase product of proto-oncogene - increase activity of each protein molecule produced by gene |
| Ras gene: | stimulates cell cycle (proto-oncogene) |
| p53 gene: | tumor-suppressor gene - functions: halt cell cycle for DNA repair, turn on DNA repair, activate apoptosis |
| Embryonic development occurs... | when gene regulation proceeds correctly |
| Cancer occurs... | when gene regulation goes awry |
Created by:
tessamcelrone
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