Biology 2- UH BIOL 1362 Week 7 Notes- Meiosis and DNA Replication
Biology 2- UH BIOL 1362 Week 7 Notes- Meiosis and DNA Replication BIOL 1362
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This 6 page Class Notes was uploaded by Alexis Clowtis on Monday March 7, 2016. The Class Notes belongs to BIOL 1362 at University of Houston taught by CHEEK in Spring 2016. Since its upload, it has received 18 views. For similar materials see Biology 2 in Biology at University of Houston.
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Date Created: 03/07/16
Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 3/1/16 Exam Refresh Final has 3-4 questions per midterm topics missed by >50% of class Can earn up to 10 pts to add to relevant midterm grade These Q’s are optional Can only add points not take away, max is 100 Clicker- Built up tolerance offspring as built up as they had it; Answer: intensive use passed to offspring (Lamarck’s) Actual test questions: How could resistance increase? Answer: NOT lamarck’s because can’t pass on enhanced traits; offspring “start over” Correct is natural selection: resistance bacteria reproduced and/or spontaneous mutation Clicker- 2 heterozygous individuals for 1 trait crossed= monohybrid cross Test: Eggplant skin color question from exam: 1 gene probably controls fruit skin color because PpXPp gives 675 purple, 217 white skinned Meiosis increases genetic diversity in offspring 1. Crossing over: creates recombinant chromosomes 2. Independent assortment: randomizes which one of homologous chromosome pair enters a gamete (line up RL or LR at metaphase plate) 3. Fertilization: combines chromosome sets from 2 different individuals [Pictures] Crossing over: Figure 10-11 (pg 203 of textbook) Independent assortment: M I P or P I M metaphase (Figure 10-10) 2 = # of possible ways homologous pairs could assort (line up) Fertilization: each egg has 2 possible, each sperm has 2 n multiple ^ together to get possibilities for fertilization (which is why you’re not like your brother/sister) Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek- 3/1/16 Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek Chapter 13- DNA: The molecular basis of inheritance 3/3/2016 DNA is the genetic material Known by 1920’s: chromosomes contain genetic material and are made of DNA and protein Debate: which molecules are genetic materials? Proteins? o Thought proteins because 20 amino acids gives more combinations than 4 bases of nucleotides Video: - Fredrich something- isolated nucleic acid - 1928: pneumoniae mouse experiment (Frederick Griffith)- pg 246 textbook o R strain- alive o S strain- dead o Dead S + live = alive S strain something had to change dead S to living by R because had to be DNA changing because DNAase destroyed DNA and mouse lived so it’s responsible - 1953: Watson worked with crick for structure of DNA o Found that # of nucleotides wasn’t random A=T, C=G o Didn’t do a single lab experiment themselves Experimental evidence DNA is genetic material in bacteria DNA is genetic material in viruses In bacteria and eukaryotes, DNA nucleotides occur in same ratio o %A=%T, %C=%G (ratios not the same as each other in all organisms, just when you know A, you know T etc. in everyone) Mouse experiment (inactivating molecules to figure out how R S) o Results: R + heat inactivated S cells mice die R + S with inactivated protein mice die R + S with inactivated RNA mice die R + S with inactivated DNA mice LIVE! *inactivated by enzymes that “eat” their respective molecules* Summary vs Inference Summary: states what happened in experiment (facts only) Inference: suggests what those facts mean (outcome means) Clicker- Inference from experiment- S cell DNA can transform R into infectious is a fact Answer: DNA not protein is the genetic material of bacteria Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek Hershey and Chase 1952 (to reaffirm DNA is genetic material) - T2 phage and Escherichia coli (E. coli) cells (virus infecting bacteria) o Virus is made of protein coat with DNA inside (no other machinery) - Infection: T2 reprograms host bacteria to make more viruses o How? Protein or DNA? Approach: Label DNA vs Protein (tag) Grow virus in medium containing radioactive isotope isotope: colorless, but differ in atomic mass S= 16 protons + 16 neutrons 35S= 16 protons + 19 neutrons Radioactive nuclei spontaneously give off particles and energy Grew some virus in 35S –sulfur in amino acids Grew some virus in 32P –phosphorous is in DNA (Figure 13.4 pg. 247 in textbook) Clicker- Would virus growing in radioactive sulfur synthesize DNA containing radioactive sulfur? Answer: No because DNA doesn’t contain sulfur, just phosphorus, nitrog. Base and sugar Clicker- What does radioactive phosphorus in pellet mean? Answer: viral DNA is in bacteria - radioactive sulfur outside pellet means? Answer: viral protein is outside bacteria -which is inference? Answer: DNA is genetic material is virus Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek Chargoff: investigated nitrogenous base composition of different organisms (already knew that DNA is polymer of nucleotides) -% adenine, guanine, cytosine, thymine in at least 40 species from various kingdoms Ex. %A %G %C %T E. coli 24.7 26.0 25.7 23.6 Sea urchin 32.8 17.7 17.3 32.1 -Rule: amount of A≈T, C≈T Clicker- bases occur in similar proportions? C and G, A and T DNA structure - Monomer= nucleotide - Nucleotide consists of: o 5 carbon sugar o Phosphate group o Nitrogenous base - Polymer has 2 different ends- a 5’ end and a 3’ end 5’/3’ Carbons Start counting clockwise from 0 in sugar ring 1’ C bonded to base 3’ C has an –OH group *enzymes recognize hydroxyl group always add to 3’ end* 5’ C links to 4O (phosphate) group Biology 1362- 8:30am TTH SW 102 Doctor Ann Cheek Each DNA molecule consists of 2 strands Arranged in antiparallel (subunits run in opposite directions) in a double helix Deoxyribose sugars and phosphate groups are on outside of helix and nitrogenous bases project to the inside DNA Replication Conceptual model: Watson and Crick -strands separate - complimentary bases are added to single original strand Clicker- DNA replication is in what phase? Answer: interphase- S phase Rosalind Franklin- X-ray diffraction photo of DNA which aided Watson and Crick to show structure of DNA is double helix (page 251 in textbook) Base pairing is 1 pyrimidine and 1 purine because it results in a uniform diameter (2 purines is too wide, 2 pyrimidine is too narrow)
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