PBIO 1210 Test 2 Study Guide
PBIO 1210 Test 2 Study Guide Pbio 1210
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This 10 page Study Guide was uploaded by Maddi Huff on Sunday October 2, 2016. The Study Guide belongs to Pbio 1210 at University of Georgia taught by Momany in Fall 2016. Since its upload, it has received 71 views. For similar materials see Principles of Plant Biology in Plant Biology at University of Georgia.
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Date Created: 10/02/16
Key- vocabulary PBIO 1210- Principles of Plant Biology Test 2 Study Guide DNA Replication 1. DNA a. DNA molecules are comprised of thousands of nucleotides joined together in a chain by their phosphate groups b. Nucleotide- base + deoxyribose sugar + phosphate c. 4 different bases: i. two purines; double ring (adenine and guanine) ii. two pyrimidines; single ring (thymine and cytosine) 2. Double Helix a. DNA- double helix nucleotide chains held together by hydrogen bonds between adenine and thymine (2) and between guanine and cytosine (3) b. twisted ladder with the bases forming the steps and the deoxyribose- phosphate forming the two sides of the ladder c. two strands are not identical but complementary 3. Replication (DNA ->DNA) a. DNA replication- hydrogen bonds between bases broken b. Each single strand has the information to make a new complementary strand i. T in the original strand, an A will be placed opposite it in the new strand ii. Many enzymes and cofactors required. iii. Replication starts at a specific sequence called an origin of replication iv. Helicase enzymes break the hydrogen bonds between bases v. DNA polymerases synthesize the new strand recognizing each base and attaching the correct complementary base 4. Repair a. Errors i. Mistakes sometimes during replication ii. chemicals and UV light b. If the damage is not repaired i. change in DNA (mutation) may be passed on to other cells. Can be good or bad c. Several enzymes work to repair damage i. DNA polymerases can reverse themselves and go back to repair damage during replication ii. DNA repair nucleases can cut out damaged pieces of DNA and then put in the correct bases iii. DNA ligase connects the repaired section to the main strand 5. Genetic code a. 4 bases in DNA (ACGT) -> 20 amino acids Key- vocabulary b. code is triplet- a sequence of 3 nucleotides (codon) along the DNA strand calls for particular amino acid c. Gene- the linear sequence of nucleotides in DNA that designates all the amino acids in a protein or polypeptide chain 6. RNA a. Messenger RNA (mRNA) b. ribosomal RNA (rRNA) c. Transfer RNA (tRNA) d. Structure i. Nucleotides (base + ribose sugar + phosphate) joined together in a chain by their phosphate groups (similar to DNA) ii. RNA Nucleotides: same bases as found in DNA except uracil replaces thymine iii. RNA molecules are single stranded iv. some parts of RNA molecules may be folded to have sections that are double stranded. 7. Transcription (DNA -> RNA) a. mRNA synthesized by copying one strand of DNA in a complementary fashion b. RNA polymerases attach at a promoter region on DNA c. Open up the DNA double helix d. Add complementary nucleotides and connect to make an RNA e. Carries the genetic instructions to the cytoplasm where protein synthesis occurs f. in eukaryotes, mRNA must be processed before leaving the nucleus g. Introns (sequences that do not code for protein) are cut out h. Exons (code for protein) remain i. To prevent degradation by RNAses in the cytoplasm i. Cap is added at one end ii. Tail of adenine bases is added at the other end 8. Translation (RNA -> protein) a. Genetic code i. Triplet/codon- a sequence of 3 nucleotides along the DNA strand calls for particular amino acid ii. Redundant- more than one codon for most amino acids iii. one start codon- only codon designating the amino acid methionine iv. 3 stop codons b. Ribosomes made of protein and RNA (rRNA) c. Two subunits i. a smaller one with a binding site for mRNA ii. larger one with 3 binding sites for tRNAs d. tRNAs (adaptor) i. Different tRNA for each codon- each is folded in a characteristic way with stems and loops ii. One of the free ends of the tRNA has an attachment site for an amino acid iii. Specific enzyme (aminoacyl-tRNA synthetase) recognizes the shape of the tRNA and attaches the correct amino acid Key- vocabulary iv. In the loop opposite the free ends, 3 bases anticodon v. complementary to the codon for the amino acid that is attached to the tRNA e. Initiation i. Initiator tRNA (methionine) and mRNA attach to the small ribosomal subunit ii. anticodon of the tRNA attaches to the start codon on mRNA iii. The larger ribosomal subunit attaches to the smaller subunit f. Elongation i. tRNAs with amino acids attach to ribosome and to the mRNA codons complementary to the tRNA anticodons ii. A site- Aminoacyl-tRNA receiving site iii. Peptide bonds are formed between the amino acids, and the ribosome moves down the mRNA g. Termination i. At stop codon ii. a cytoplasmic protein binds to the mRNA iii. ribosomal subunits separate iv. mRNA and the protein are released Genetic engineering 2. DNA Differences a. Individuals within species differ in the exact sequence of bases in DNA b. Differences in gene sequences coding for specific proteins or rRNA can be used to estimate relatedness of individuals and species. c. Differences can be viewed giving “DNA fingerprint” (unique pattern) 3. DNA fingerprinting a. DNA fingerprinting can be used to i. help identify criminals ii. demonstrate innocence iii. identify victims of disasters iv. Establish family relationships 4. RFLP (restriction fragment length polymorphisms) a. Restriction enzymes from bacteria cut DNA molecules at specific sites. i. purpose may be for bacteria to degrade foreign DNA. ii. Restriction enzymes cut each strand of DNA at recognition sequence b. Cutting DNA with restriction enzymes produces fragments of DNA i. genetic differences and mutations, some recognition sequences will be in different places in different individuals ii. some pieces longer than others iii. different patterns c. Electrophoresis i. DNA in electric current in gel ii. DNA is negatively charged, moves to + pole iii. Smaller pieces move faster iv. DNA fragments stained to that they are visible v. Sizes compared with known standard or each other 5. Polymerase Chain Reaction (PCR) Key- vocabulary a. For very small amounts of DNA b. DNA polymerase enzyme is used to copy and increase the amount of DNA c. Heat stable DNA polymerases important for PCR i. Thermostable enzymes that are stable at higher temperatures than those of most organisms d. High temp 95ºC (around 200ºF) i. the hydrogen bonds ii. Two strands of DNA separate e. Temperature is lowered (50ºC) i. Strands replicated if DNA polymerase and the nucleotides are present ii. After DNA replicated, heat again to separate new strands and start replication again. f. Thermostable DNA polymerase survives repeated cycles of heating and cooling and is still active g. Repeated cycles of this process produces many copies of what was originally a small amount of DNA 6. Sequencing a. Fragment of interest is amplified by PCR b. Complementary fragments of DNA are made with terminator NTPS (when it gets incorporated into new chain, stopping elongation) that are fluorescently labeled c. Tags are colored to differentiate them 7. Forensics a. 0.1% of DNA (about 3 million bases) differs from one person to the next. b. Variable regions for DNA are used to profile an individual i. samples from blood, bone, hair, and other body tissues and products. c. While there is a chance that someone else has the same DNA profile for a particular probe set, the odds are exceedingly slim. d. VNTR (variable number of tandem repeats) DNA sequences with runs of short, repeated sequences, such as GTGTGT i. 4 to 40 repeats in different individuals. ii. Individuals usually inherit a different variant of each VNTR locus from their mother and from their father iii. two unrelated individuals therefore do not usually contain the same pair of sequences. iv. There are many VNTRs in human genome. 8. Genetic engineering a. Based on ability to move genes from one organism to another b. Traditional Crop Breeding c. Natural selection: survival of an organism depends on how well it can survive and reproduce in environment d. Artificial selection- humans improved crops by planting seeds from best plants e. Genetic engineering- enzymes that are naturally present in one organism used to alter the genetic makeup of another organism Key- vocabulary i. Genetically modified organisms (GMOs) ii. Genetically engineered organisms (GEOs) iii. Transgenic organisms f. Changes made in the DNA of the organisms so these changes are passed on g. Drugs purified from large populations of bacteria i. some were very scarce because they could only be obtained from cadavers ii. Genetically engineered bacteria iii. interferon (fight viral infections) iv. human insulin (treat diabetics) v. human growth hormone 9. Other Uses of Genetic Engineering a. Plants can be genetically engineered to increase tolerance to environmental stress and produce more and better crops b. Gene therapy: replacing a defective (mutated) gene with healthy version c. Tools of Genetic Engineering i. Restriction enzymes (scissors)- recognize specific sequence in a DNA molecule and cut through one strand of DNA at that point. They are produced by bacteria to protect from foreign DNA ii. Ligases (glue)- join pieces of DNA together and repair enzymes iii. DNA polymerases- enzymes that link nucleotides together to form DNA strand. 1. Thermostable polymerases used for PCR 2. Reverse transcriptase- makes DNA copy from RNA copy (reverse of normal transcription) a. When infect cells, make DNA copies of themselves to replicate inside a cell d. GE in bacteria i. Much of genetic engineering is done in bacteria, especially Escherichia coli 1. Fast growing (20 minutes) 2. Easy to manipulate ii. Plasmids: small pieces of DNA usually circular, typically contain a few genes (1-5kb, 1-5 genes) 1. Can insert genes of interest using “cut and paste” 2. Often encode antibiotic resistance genes 3. can be transferred between some bacteria e. GE in plants i. Foreign DNA inserted into individual plant cells which can be grown into complete plants using plant hormones and tissue cultures 1. Plasmid DNA and viruses 2. Electroporation: electric field makes temporary holes in cell membranes to allow uptake of foreign DNA 3. Gene gun is a device that shoots gold or tungsten particles coated with foreign DNA into plant cell f. GM crops Key- vocabulary i. Crops have been engineered to resist insects, resist herbicide, better absorb phosphate from soil, and produce antibodies and vaccines Mitosis 1. Cell cycle- sequences of changes that a cell passes though between divisions a. Relatively long time duplicating structural components i. chloroplasts, mitochondria, membranes, DNA b. Relatively short time in cell division i. Cell division: division of components leading to two daughter cells c. Ploidy- the number of sets of chromosomes in the nucleus of a cell i. Haploid- typically gametes such as egg or sperm ii. Diploid-zygote 2. Chromosomes a. Characteristic number of chromosomes for each species b. Homologous pair of chromosomes i. Each homologous chromosome contains genes for the same traits as the other homologous chromosome ii. One from mom, one from dad iii. Two chromosomes: diploid (2n) 3. Cell cycle a. Interphase- long phase cell replicates chromosomes and synthesizes other cell constituents. b. Interphase- G1, S, and G2 4. Interphase: G1 a. G1 (Gap1) Phase i. Cell increases in size, synthesizes enzymes, ribosomes, membranes, microtubules and microfilaments ii. Mitochondria and chloroplasts replicate iii. In plants, nucleus migrates to center of cell and is held in place by a sheet of cytoplasm containing microtubules and filaments iv. The first checkpoint is at the end of this phase 1. stops cycle if conditions are not favorable, or may signal beginning of next phase. 5. Interphase: S phase a. S Phase- replication of DNA and histone proteins. i. Sister chromatids- replicated chromosomes ii. 2 exact copies stay attached to each other at centromere iii. Centromere: region where sister chromatids are attached. iv. Appears as constriction 6. Interphase: G2 a. G2 Phase Key- vocabulary i. Final phase of rapid protein synthesis, especially of microtubules and filament ii. at the end of this phase, DNA starts to condense to form chromosomes iii. Checkpoint at the end of this phase, which may stop the cycle if conditions are not favorable or if mistakes in DNA replication 7. Mitosis: Prophase a. DNA condenses: threadlike strands -> chromosomes. i. Each chromosome was duplicated in S ii. Two identical “daughter” chromosomes (called chromatids) joined together at the centromere b. Microtubules appear and line up along the spindle axis with tubules converging at the poles away from the equator of the spindle c. Nuclear membrane starts to break down 8. Mitosis: Metaphase a. Each chromatid develops kinetochore i. Kinetochore- protein complex attaches to microtubules extending toward one pole ii. Kinetochore of the sister chromatid attaches to microtubules extending to the opposite pole iii. Microtubules tug chromatids in opposite directions until line up along the equator of the cell iv. Cohesin proteins hold chromatids together 9. Mitosis: Anaphase a. Sister chromatids separate at the centromere and move apart towards opposite poles i. separate enzymes cut cohesins b. After separation, chromatids are called daughter chromosomes 10.Mitosis: Telophase a. New nuclear envelope forms around the two new sets of chromosomes b. Spindle disappears c. DNA decondenses 11.Cytokinesis a. Phragmoplast: microtubules and microfilaments b. Forms between 2 daughter nuclei c. Secretory vesicles from the Golgi form a cell plate at the center of the cell d. Cell plate grows out toward the edges e. Cell membrane and new cell wall form Meiosis 1. Mitosis- Produces 2 diploid cells with identical genetic content as parent cell a. Human: Most body cells b. Plants: most plant cells Key- vocabulary 2. Meiosis- Produces 4 haploid cells with half the genetic content of parent cell (Reduction division), variation in which version of each chromosome (mom or dad) a. Human gametes: Eggs, sperm b. Plant gametes: Eggs, sperm, pollen, spores c. Zygote: Results from fusion of gametes d. Meiosis gives potential for new combinations i. Variation is the raw material that natural selection works on (evolution) 3. Meiosis I a. Prophase I i. Chromosomes condense, nuclear envelope disappears, spindles form ii. Homologous chromosomes pair (one from mom and one from dad) and line up iii. Crossing over- homologous chromosomes lined up together, can exchange genetic material from the same part of the chromosome b. Metaphase I i. homologous pairs of chromosomes line up either way relative to each other at the center of the cell ii. Attached to spindle microtubules c. Anaphase I i. Homologous pairs separate to different cell ii. Duplicated chromatids go to the same cell at the end of meiosis 1. Nondisjunction- homologous pairs do not separate from each other in anaphase I and both go to one new cell 2. gametes have extra or missing 3. In humans, nondisjunction of chromosome #21 may result in a child with Down’s syndrome (3 copies of chromosome 21 or trisomy 21) d. Telophase i. In most organisms, there is only a partial telophase ii. Chromosomes start to uncoil, nuclear envelope starts to reform– iii. some organisms skip telophase I 4. Meiosis II (Extremely similar to mitosis) a. Prophase II i. Chromosomes condense, nuclear envelope disappears, spindle forms b. Metaphase II i. Chromosomes (pairs of sister chromatids) line up at center of cell (attached to spindle microtubules) c. Anaphase II- Centromere divides and chromatids are pulled to opposite poles d. Telophase II- Chromosomes decondense i. Nuclear envelopes reform ii. The final result of meiosis is 4 haploid cells. Polyploidy Key- vocabulary 1. Polyploid plants a. Larger cells b. Larger plants c. Polyploid variations of plants are deliberately created d. When a newly-arisen tetraploid (4n) plant tries to breed with its ancestral species, triploid (3n) offspring are formed. i. They are sterile because they cannot form gametes with a balanced assortment of chromosomes ii. However, the tetraploid plants can breed with each other 2. Polyploidy also occurs naturally in certain plant tissues a. Endoreplication: S phase of the cell cycle without the subsequent completion of mitosis and/or cytokinesis b. Seedless watermelons are produced ontriploidplants- three sets of chromosomes prevent meiosis and plants cannot produce fertile gametes i. They are produced by crossing diploid and tetraploid lines of watermelon, with the resulting seeds producing sterile triploid plants 3. Life cycles a. Asexual Reproduction- Mitotic i. simple life cycles producing the same asexual reproductive structures each generation ii. Organism haploid (1n) or diploid (2n) b. Sexual Reproduction: Meiotic i. Complex life cycles with haploid (1n) and diploid (2n) stages and specialized reproductive cells ii. Three basic types of sexual life cycle: gametic, zygotic and sporic c. Sexual Reproduction: Gametic i. Typical of animals and some algae ii. Adult diploid (2n) organisms produce gametes by meiosis iii. Gametes are the only haploid stage in the life cycle. iv. All cells except gametes diploid (2n) v. Advantage: if gene on one homologous chromosome mutated, the corresponding gene (allele) on the other homologous chromosome may be normal, allowing the organism to survive. d. Sexual Reproduction: Zygotic i. Common in protists (algae, protozoa, and other simple eukaryotes) ii. Organisms haploid (1n) during most of life cycle iii. Only zygote is diploid (2n) iv. Advantage: Following meiosis, gametes can be produced quickly by mitosis. v. Advantage: Thick walled zygotes can survive unfavorable conditions 1. When environment improves, zygote undergoes meiosis producing spores that grow into new offspring. vi. Disadvantage: no genetic redundancy during most of its life Key- vocabulary vii. It cannot carry along mutated genes that might be useful in a changed environment. e. Sexual Reproduction: Sporic i. All land plants, some algae ii. Alternation of Generations: 1. Plants have a diploid (2n) stage (sporophyte) that produces spores by meiosis 2. Spores grow into a haploid stage (1n) (gametophyte) that produces gametes by mitosis 3. gametes fuse to produce zygote that grows into a sporophyte 4. Plants differ in importance of each stage
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