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21 Cards in this Set
- Front
- Back
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cell |
-structural unit of organisms -all living things except viruses are made up of cells |
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3 major components of cells |
1. PM: membrane that isolates the cell from the outside envmt 2. nuclear region: directs cellular activities, surrounded by nuclear membrane, contains majority of genetic material 3. cytoplasm: material between nuclear region and plasma membrane |
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types of cells/organisms |
-determined based on structure of nuclear region: 1) prokaryotes: bacteria + relatives - genetic material in single circular DNA molecule with no nucleus or nuclear region; no nuclear membrane; DNA not highly condensed in cell division (not visible during cell division) 2) eukaryotes: contain a nucleus surrounded by a nuclear membrane; DNA contained in nucleus and located on chromosomes; organelles within cytoplasm |
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types of eukaryotic cells |
1. animal 2. plant -essentially the same except plants have vacuoles, chloroplasts, cell wall for structure |
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eukaryote genes are found in: |
1. nucleus (chromosomes) 2. mitochondria (circular prokaryotic) 3. chloroplasts (circular prokaryotic) -mostly on chromosomes in nucleus |
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mitochondria & chloroplasts |
-mitochondria: respiration -chloroplasts: photosynthesis -chloroplast genome larger than mitochondria genome -mitochondria and chloroplasts divide by simple fission like bacterial cells (split in two) |
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endosymbiont hypothesis |
-mitochondria and chloroplasts were once free-living organisms that were engulfed by a eukaryotic cell and began a symbiotic relationship |
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genetic material in prokaryotic and eukaryotic organisms |
-deoxyribonucleic acid (DNA) -responsible for inheritance of characteristics from mother cell to daughter cells or parent to offspring |
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characteristics of functional DNA |
1. chemical complexity and stability: to encode and store genetic info 2. accurately replicate: offspring receive identical copes, no mutations 3. expression of genes/traits 4. ability to slowly mutate: genetic diversity, adaptability to changing environment (contrasts with first two) *"know these bullets"* |
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genetic material in some viruses |
-ribonucleic acid (RNA) -viruses may be RNA or DNA based -e.g. Tobacco Mosaic Virus (TMV): purified RNA spread on tobacco leaves results in lesions |
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Fraenkel-Conrat & Singer experiment |
-1956 -question: what substance (RNA or protein) carries the genetic material in TMV? -Type A + Type B = two different strains -Type A RNA mixed with Type B protein to create hybrid: hybrid = RNA A + protein A -Type B RNA mixed with Type A protein to create hybrid: hybrid = RNA B + protein B -conclusion: RNA was genetic material of TMV -the source of the RNA always determines the type of TMV that you obtain |
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structure of RNA and DNA |
-RNA and DNA are linear polymers of nucleotides -nucleotides consist of: 1. deoxyribose/ribose: pentose (5 C) sugar 2. a phosphate group (on 5' carbon) 3. a nitrogenous base: purine or pyrimidine -double-ringed purines: A + G -single-ringed pyrimidines: C + T (DNA) + U (RNA) |
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pentose sugars |
-phosphate group on 5' -hydroxyl group on 3' -nitrogenous base on 1' -differ in an O on 2' |
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building a nucleotide |
-each N base is linked on deoxyribose at 1' carbon = nucleoside (base + sugar) -phosphate group then attached to 5' carbon of nucleoside = nucleotide (base + sugar + phosphate group) -pic: left = ribose, right = deoxyribose, note N base attached at 1' and P group at 5' |
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building a polymer or polynucleotide chain |
-nucleotides are then joined together by phosphodiester bonds to form a polynucleotide chain -one end is the 5' end: 5'-P -other end is 3' end: 3'-OH |
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Chargaff's Rules |
-1940s
1. the base composition of a DNA molecule has an equal amount of purines as pyrimidines in a given individual (%C=%G, %A=%T) 2. the composition of bases differs between species but remains constant within an organism |
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discovery of double helix |
-Franklin & Wilkins: characterized shape of DNA molecule using X ray diffraction, data indicated DNA was helical (found best pic of DNA shape) -Watson & Crick: first to construct an accurate model of DNA accounting for A-t and G-C base correlation and helical arrangement (looked at pic and determined it was a double helix) -first 3-D model was built with wire and paper: two chains of DNA, oriented in opposite directions and coiled around a central axis to form a right-handed double helix |
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features of the double helix |
1. two strands run in opposite directions and are complementary (A db T, C tb G) -weak H bonds hold two complementary strands together (but between nucleotides, strong phosphodiester covalent bond) 2. double helix makes a right-hand turn 3. DNA sequence is unrestricted: unlimited in terms of codes possible to produce proteins (only 4 bases but many diff combinations) 4. forms minor and major grooves within DNA structure -various proteins packed into these grooves to protect/provide structure to DNA molecules |
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DNA structure |
-labeled at 3' and 5' ends -typically drawn as horizontal ladder (base pairs = rungs, sugar/phosphate backbone) -oriented 5' to 3' (coding strand = top strand, complementary strand = bottom strand) -5' end is phosphorylated -3' end has hydroxyl group |
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differences between RNA and DNA |
-RNA: ribose sugar, uracil, single stranded, chemically less stable -DNA: deoxyribose sugar, thymine, double helix, chemically more stable -RNA less stable b/s single stranded and b/c hydroxyl group makes more reactive |
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roles of RNA |
1. genetic code of certain viruses 2. involved in gene expression (major role): mRNA, snRNA, tRNA, rRNA 3. involved in gene regulation (faster/slower rate): miRNA, siRNA 4. discovery of catalytic RNA molecules (ribozymes) led to hypothesis that life may have started with RNA as the genetic material - single stranded -still 5'-P to 3'-OH -U instead of T -unique structures possible |
