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 Review 16-18  The search for the genetic material involved many experiments  Griffin-transformation  Hershey/Chase –Sulfur/Phosphorus.

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Presentation on theme: " Review 16-18  The search for the genetic material involved many experiments  Griffin-transformation  Hershey/Chase –Sulfur/Phosphorus."— Presentation transcript:

1  Review 16-18  The search for the genetic material involved many experiments  Griffin-transformation  Hershey/Chase –Sulfur/Phosphorus

2  Franklin & Wilikins/Watson & Crick-double helix w/bases in middle held together by H-bonds  Antiparallel  Chargoff’s base-pairing rules-A/T & C/G  Transformation-assimilation of external DNA into a cell

3 DNA replication: Begins @ origin of replication (bubbles) Helicase- separates strands Ss binding proteins stabalize strands Leading strand is made by DNA pol adding nt’s 1 by 1 in the 5’ to 3’ direction

4  Primase attaches to other strand & makes RNA primer for Okazaki fragments  DNA pol adds nt’s to the primer fragment  Ligase binds the fragments together by covalent bonds

5  DNA pol’s proofread nt’s & if 1 is found to be wrong it takes it out & replaces it  Mistakes not caught right away are cut out later by enzymes called nucleases  This is called nt excision repair

6  Telomeres-nt seq’s at the ends of chromosomes  They protect DNA from being eroded after many cycles of replication  They protect the genes on the end of chromosomes  They get shorter w/each replication & are shorter in older people’s cells

7  Telomerase-lengthens the telomeres in germ cells & compensates for the shortening that occurs w/replication  Not active in most somatic cells  Germ cells give rise to gametes

8  Ch 17  From gene to protein  DNA- A T C G; ds  RNA- A U CG; ss  Adenine is in DNA, RNA, & ATP

9  1 gene 1 pp  Txn-in the nucleus it is written from DNA template  mRNA processing-then the introns are cut out & a cap & tail is added  In the cytoplasm it is translated at the ribosome into a pp

10  Codons-3 letter words that code for each aa during tsln  Look at pg 314  What is the possible seq of nt’s in the template strand of DNA that would code for the pp phe-leu-ile-ala-val?

11  Aaa-gaa-taa-cga-caa  What pp will be made from  Aug-ucu-uca-uua-ucc-uuu?

12  Met-ser-ser-leu-ser-phe  Txn 3 stages  Initiation, elongation, termination

13  Initiation begins w/initiation complex  A promoter region on DNA  Including the TATA box ~25 nt’s upstream from start point  Txn factors bind to help RNA pol bind  DNA strands unwind  RNA pol transcribes mRNA

14  Remember way back to cell signaling?  Txn factors can be signals from hormones or other molecules  Used to turn genes on or off by blocking txn

15  Elongation  RNA pol moves downstream unwinding DNA and elongating RNA transcript in 5’ →3’ direction  Double helix reforms as RNA pol moves on down the line

16  Termination  Eventually RNA is released and RNA pol falls off  Not yet completely understood what mechanism causes this

17  Modification of RNA B4 leaving nucleus  Introns (non-coding regions) are cut out  A polyA tail is added to 3’end & a cap is added to 5’ end

18  Evolutionary role of introns:  Some have seq’s that control gene activity  Some genes code for more than 1 pp depending on which segments are treated as exons during RNA processing  This is alternative RNA splicing

19  **The presence of introns allows exons to be moved around more easily (exon shuffling) making new proteins w/new combinations of functional domains

20  Tsln also 3 parts:  Initiation, elongation, temination  The players: mRNA, tRNA, aminoacyl-tRNA synthetase, ribosomes  Structure of tRNA  aa at 1 end & anticodon on other end  Anticodon is complemetary to codon

21  The function of the ribosome in pp synthesis is :  To hold the mRNA & tRNA together,   catalyze the addition of aa’s form tRNA’s to the pp chain,  & to move the mRNA along & eject tRNA during translocation

22  initiation stage of tsln  Brings together mRNA, tRNA bearing the 1 st aa of the pp, & 2 subunits of a ribosome

23  The small ribosomal subunit binds w/mRNA  An aminoacyl-tRNA binds to the A site  A peptide bonds forms b/w new aa & pp  tRNA translocates to P site  tRNA leaves P site & P site is vacant until another tRNA has given up their aa

24  Termination  The final stage of tsln is termination  the ribosome reaches a stop codon in the mRNA  The pp may undergo further modification B4 it becomes a functional protein

25  A polyribosome is a group of ribosomes the read a single mRNA at the same time

26  While it’s being made the pp will start to fold & coil spontaneously  But…b4 it can do it’s job some aa’s made be modified by the addition of sugars, lipids, phosphate groups, etc….  Sometimes the pp is cut into pieces b4 it is functional

27  If the pp is destined for the endomembrane system or secretion it’s marked by a signal peptide  This targets the pp to the ER

28  The signal peptide is recognized by by SRP’s (signal-recognition particle)  The signal is usually removed & then the rest of the pp is finished  If it is to be secretory protein it is released into ER soln

29  Mutations- point mutations are the most common kind  They are the change of 1 nt  Substitutions usually missense (codes for aa but not the right one)  Nonsense mutation (point mutation that codes for a stop codon where there should not be one)

30  Pro’s vs Euk’s  Prok have circular DNA & so don’t have telomeres & has only 1 origin of replication  Txn & tsln take place at the same time in prok’s (prok’s have no nucleus)  Prok’s don’t have introns!

31  Ch 18  Viruses have a genome but can only replicate w/in a host cell  Viruses are obligate parasites b/c they cannot reproduce outside of a host cell

32  Phages can have 2 types of life cycles  lysogenic- viral DNA is replicated w/host DNA  Lytic cycle- (virulent phages) host is destroyed after making many baby viruses

33  Viral structure is a nucleic acid which can by ss or ds DNA or RNA  surrounded by capsid (protein shell)  ** ONLY some viruses have a viral envelope  Viruses that use ssRNA & reverse transcriptase are retroviruses

34  Vaccines & nucleoside analogs (interfers w/viral nucleic acid synthesis) are the only effective weapons against viruses  Viroids are the simplest infectious biological systems  Prions are misfolded versions of normal brain proteins

35  Gene transfer & recombination in bacteria  Transformation-external DNA is assimilated by a cell  Transduction-DNA is transferred from 2 bacteria to another by a virus

36  Transposition-A seq of DNA is moved to alternate locations in the genome  Conjugation-a group of F+ bacteria is mixed w/group of F- bacteria (after days all are F+)  Also a plasmid is exchanged via a pilus

37  What is an operon?  A promoter, operator, & the genes they control  They are all part of the DNA  An operon can be turned off by a repressor (protein) that binds to the operator & blocks txn by blocking the attachment of RNA pol

38  The repressor is a product of a regulatory gene (in this case called trpR)  Regulatory genes are always on at a low rate  An inducer inactivates the repressor

39  What is a ligand?

40  EXPLAIN replication in detail  EXPLAIN how a gene in a eukaryotic cell is transcribed & translated to produce a protein. Draw these processes & label RNA Polymerase, pre-mRNA, mRNA, introns, exons, spliceosome, ribosome, tRNA, codon, anticodon  EXPLAIN what changes may occur to the mRNA b4 it leaves the nucleus  EXPLAIN how the genetic material from 1 bacterial cell enters another via transformation, transduction, or conjugation

41  In fruit flies, the phenotype for eye color & wing shape is determined by certain loci. E indicates the dominant allele and e indicates the recessive allele for eye color and W is normal wings and w is vestigial wings. The cross between a fruit fly with wild-type eyes and vestigial wings & sepia eyes with normal wings (wild-type) yielded the following results for the F1 generation:

42  Wild-type sepia/normal wild-type/vestigial sepia/vestigial   F1100000  F25216239  Determine the genotypes of the Parental (P) generation.  Show a Punnett square cross of the P generation and the F1 generation (to show the expected F2 results)  Use the Chi-square test to determine your chi-square value of the observed vs. expected ratios.  How many degrees of freedom is there in this analysis?

43  A virus is an infectious particle that replicate using the metabolic machinery of their bacterial, animal, or plant host. Viral infections may destroy the host cell and cause disease within the host organism.  Describe the basic structure of a virus  Why are they not considered alive?  What is a prion?  How does a vaccine work?


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