DNA Structure and replication Flashcards
Central dogma
DNA-transcription-RNA-translation-protein
Chromosome Theory of inheritance
chromosomes carry genetic material across generations
- though to contain proteins and nucleic acids
what did two strains of Pneumococcus that Frederick Griffith use tell us?
A single gene mutation change can convert an S strain to R strain of the same antigenic type
- Smooth cause fatal pneumonia in mice
- Rough was not fatal
Discovery of transformation
Non-virulent IIR were transformed into virulent III S cells
Griffiths proposal
- the transformation factor as the molecule transformed the RII into SIII
- The transforming factor carried hereditary information
- ## Described as transformation
What is the transforming principle
DNA
Transformation
Taking up naked exogenous (outside) DNA
- is a genetic event (transferred into generations)
- variation is broad
bacteriophages(phages)
Viruses that infect bacteria
- DNA is responsible for pages infection of bacteria cells
T2 phages anatomy
- have protein shell
- tail segment (attaches to host cell-bacteria wall)
- head that contains DNA
T2 and E. Coli experiment
- T2: 50% protein, 50% DNA
- infections is initiated by T2 tail fibers
- New viruses are produced inside bacterial cell
What is the genetic material in T2
DNA not protein
nucleoside phosphate (mono, di, tri)
- triphosphates are most significant
1. precursor molecules molecule for nucleic acids synthesis in the cell
2. adenosine- and guanosine triphos (ATP,STP) are essential in cell bioenergetics
three properties of genetic code
- must replicate
- must encode information
- must be able to change (mutable)
What are the three forms of DNA
A-form and B-form (most common), Z-form
Complementarity
Specific of A with T, and G with C - dues to specific chemical affinity between nitrogenous bases
Chargaff’s rules
- amount of adenine is proportional to thymine and amount of guanine is proportional to amount f cytosine
- The sum of purines equal the sum of pyrimidines
- sum of (G+C) does not necessarily equal the sum of (A+T)
Issues for DNA replication
- unwinding of the helix
- reducing increased coiling generated during unwinding
- synthesis of a primer for initiation
- discontinuous synthesis of the second strand
- removal of the RNA primers
- joining of the gap filling DNA to the adjacent strand
- proofreading
Basics of DNA replication
- SEMICONSERVATIVE
- BI-DIRECTIONAL
- MAIN SYNTHESIS – POLYMERASE III
- DIRECTION 5’ – 3’
- START AT POINT(S) OF ORIGIN
basics of DNA replication steps
- Unwinding and stabilizing DNA double helix
- Initiation of DNA synthesis, synthesis of RNA primers
- Continuous DNA synthesis – leading strand
- Discontinuous DNA synthesis – lagging strand
- Proofreading and correction of errors
Semiconservative DNA replication
each daughter duplex contains one parental and one daughter strand (go back and look at pictures on slide 38)
Conservative DNA replication
one daughter duplex contains both parental strands and the other contains both daughter strands (go back and look at pictures on slide 38)
Dispersive DNA replication
(go back and look at pictures on slide 38)
