BIO 207 LECTURE 2.docx

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Biology (Biological Sciences)
Lesley Harrington

BIOL207 B01 Lec02 2014-01-08 Enzymes are significant in contributing to biological, behavioural, and physiological pathways. Genes and gene products work in a sequence.As we view the results; we establish which intermediate is necessary to allow for growth. -Class example: If you add Orn, you cannot rescue the mutant; if you add something downstream from Orn, it will grow (Cit/Arg); CHAPTER 1: cont’d A. Watson, Crick and others demonstrated the structure of DNA; DNAis a double- helix structure; Watson and Crick didn’t do many experiments; they took other peoples’data and made sense of it. a. Chargaff’s rulesq (A=T), (C=G); Chargaff broke DNAinto its component (nucleotide bases);Apairs with T, C pairs with G; b. Antiparallel strands; antiparallel strands show that a 5’and 3’end exist; 5’ end adds new bases at this end; synthesis always in a 5’to 3’direction c. X-ray crystal image from Rosalind Franklin; crystallized DNAand made an X-ray diffraction; found that this was double-stranded in nature; d. Built metal models of bases e. Proposed double helix structure of DNA f. Also proposed Central Dogma – this connects DNAto phenotype; DNAis transcribed to RNA, RNAis transcribed to protein; allowed them to define genetic code  triplet codons made up basic genetic subunits for transcription RIGHT HANDED HELIX; minor and major groove  The major groove occurs where the backbones are far apart, the minor groove occurs where they are close together. B. Model organisms; Zebra fish are similar but easier to study than mice; Roundworm are transparent and it is easier to view biological function through this trait; a. A.P.O.G. (Awesome Power of Genetics/mutational analysis) led to dominance of six model organisms; see text b. Model organisms have specific practical advantages, including “small genomes”; there is very few gene duplication (extra DNA) in these organisms; small c-value; reproduce quickly, easy to maintain, short generation span  these animals reach sexual maturity in a short time (flies reach a sexual maturity in a couple of weeks); Arabdopsis reproduces every couple of weeks; pine trees take years Fast generation time, easy to grow, don’t take a lof of space in the lab Model organisms are becoming less central in genetics c. Many disease genes etc. have been identified in mutant screens in model organisms; d. New techniques (including cheap DNAsequencing) are starting to make model organisms less central in genetics; there was a bias on using model organisms… now can use the DNAof the organism you want to through cheap DNASequencing. Model organisms are really well characterized and can be applied to other organisms as well. C. C-value paradox; genome= all the DNAin the nucleus, you have 3 billion bp of DNAin our human genome; there is not a correlation between complexity and genome size a. C-value is a measure of DNAcontent (bp or pg)  the amt of DNAis not correlated with its complexity; gene number is not effective in predicting complexity either; b. No correlation between and organism’s complexity and its c-value; showed a plant that has 150 billion bp in genome, but it is not 50x more complex than humans c. Gene number does not vary as much as c-value d. Repetitive DNAmakes up most of the c-value in large genomes; repetitive DNA… will be looked at later CHAPTER 2: CHROMOSOMES Video clips: BBC Secret Universe: The Hidden Life of the Cell • Most of the time, chromosomes are decondensed; only packaged during cell division; • CHROMOSOMES ARE FOUND IN THE NUCLEUS • Chromatin DNAis DNAcovered in proteins; • 20,000 structures tell our cells what to make and when; double helix is st icon of 21 century  6 feet of DNAin the nucleus; • Once a gene has been copies, instructions are carried outside of the nucleus; mobile factories turn these instructions into proteins; each protein has its own specific shape and purpose. Cell Division A. Chromosome packaging; when chromosomes are condensed, fluorescent probes helps outline the different parts of the chromosomes; we
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