Presentation on theme: " Review 16-18 The search for the genetic material involved many experiments Griffin-transformation Hershey/Chase –Sulfur/Phosphorus."— Presentation transcript:
Review The search for the genetic material involved many experiments Griffin-transformation Hershey/Chase –Sulfur/Phosphorus
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
DNA replication: 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
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
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
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
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
Ch 17 From gene to protein DNA- A T C G; ds RNA- A U CG; ss Adenine is in DNA, RNA, & ATP
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
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?
Aaa-gaa-taa-cga-caa What pp will be made from Aug-ucu-uca-uua-ucc-uuu?
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
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
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
Termination Eventually RNA is released and RNA pol falls off Not yet completely understood what mechanism causes this
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
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
**The presence of introns allows exons to be moved around more easily (exon shuffling) making new proteins w/new combinations of functional domains
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
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
initiation stage of tsln Brings together mRNA, tRNA bearing the 1 st aa of the pp, & 2 subunits of a ribosome
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
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
A polyribosome is a group of ribosomes the read a single mRNA at the same time
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
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
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
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)
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!
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
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
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
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
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
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
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
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
What is a ligand?
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
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:
Wild-type sepia/normal wild-type/vestigial sepia/vestigial F F 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?
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?