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UCONN - MCB 2400 - Chapter 9 DNA Structure (updated) - Class Notes

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UCONN - MCB 2400 - Chapter 9 DNA Structure (updated) - Class Notes

School: University of Connecticut
Department: Biology
Course: Human Genetics
Professor: Colleen Spurling
Term: Fall 2015
Tags:
Name: Chapter 9 DNA Structure (updated)
Description: this updated set of notes now contains information from Week 1's lecture
Uploaded: 01/18/2018
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background image Chapter 9 DNA Structure Chromosomes consist of proteins and DNA Proteins were believed to be genetic material because it was more 
complicated
Two jobs of genetic material 1. Duplicate itself
2. Control the development of the rest of the cell in a specific way
Fredrick Griffith 1928 Studied pneumonia in rats and discovered two types of 
streptococcus/dipplococcus pneumoniae bacteria: 
1. Type R, rough nonvirulent o Did not develop pneumonia when injected 
o Heated along with heated Type S caused pneumonia 
(TRANSFORMATION) Type r was not found alive, only S  2. Type S, smooth virulent: enclosed in a polysaccharide which could  shield bacteria o Developed pneumonia and died
o Not affected when heated 
TRANSFORMATION DNA was transferred from S to R which allowed R to develop the 
smooth coat 
The coat allows the bacteria to hide from the immune system  Griffith could not figure out what the chemical nature of the 
transforming substance was 
Avery, Macleod, McCarty 1944 Attempted to answer Griffith’s question o Isolated components from heat-killed S cells
o Added purified molecules (lipids, sugar or nucleic acid so adding 
ONLY protein, etc.) to living R type cells o Do any purified molecules contribute to transformation? Carbs,  lipids, proteins, RNA…NO, DNA… YES, DNAse (cuts up 
DNA/instructions)…NO
o DNA contains the information to construct the polysaccharide  coat Hershey and Chase 1952
-reinforces that DNA was in fact the hereditary molecule 
Bacteriophage (bacterial cell infecting viral particle)-a very simple, 
protein coat and nucleic acid core (deoxyribose core)
background image Wanted to prove that protein did not transmit genetic info using E. coli 
bacteria infected with a virus that had a large protein “head” 
surrounding DNA
Phosphorus (DNA) but not Sulfur (protein) entered the bacterial cell 
labeled bacteriophage 
DNA contains phosphorus not sulfur so when radioactive phosphorus 
was used, viral DNA emitted radioactivity (if protein was genetic, 
bacteria would have radioactive sulfur)
Captured progeny (viral particles) phage from lysed (broke open 
bacterial cells) cells 
Progeny phage were labeled with phosphorus, but not sulfur, therefore 
DNA was passed to the next “generation”
Hereditary Material (DNA)
Characteristics hereditary material must have:
Chemical and genetic stability (faithful copies) o Ability to be passed to daughter cells while stable  Storage of great amount of information (code for all traits) Potential for change (mutation) o Generate new characteristics for evolution DNA Structure
Sugar, phosphate group, nitrogenous base
Nucleic acid…building block=nucleotide
Sugar-Deoxyribose o RNA-ribose (2’C=OH), DNA-deoxyribose (2’C=H)
o 5 atom ring, 5 carbon but only 4 C in ring
o 1’C is attachment for nitrogenous base
o 3’C has hydroxyl group that allow nucleotides to form chains 
o 4’C has 5’C attached (HOCH2) which has the phosphate group
Phosphate group-phosphorus atom bonded to 4 oxygen 4 types of nitrogen containing bases: equal amounts of adenine and 
thymine, equal amounts of guanine and cytosine (Chargaff’s rule)
o RNA-uracil instead of thymine  The race to solve the structure… Linus Pauling presented the triple helix Erwin Chargaff 1948 Chargaffs rule: DNA from any cell of all organisms should have a 1:1 
ratio or purine to pyrimidine bases and more specifically that the 
amount of G=C and A=T 
He missed the base pair rule and didn’t know the double helix Leaked to Watson and Crick
background image Rosalind Franklin 1953 Bombards DNA with x-rays and looked at the pattern after bombarded Maurice Wilkins “boss” Produced clear x-ray diffraction patterns, discovered helical form and 
position of phosphates 
“A” (crystalline) form and “B” (wetter cells) form of 3-dimensional 
structure of DNA
Watson and Crick 1953 certain of sugar-phosphate backbone covalent phosphodiester bonds between nucleotides  hydrogen bonds between of a complimentary base pair (H-bonds 
between single strands hold the 2 together into a double stranded 
molecule)
double helix, anti-parallel alignment solved the puzzle with cut-outs DNA Structure
Nucleotide- a single building block of DNA consisting of one deoxyribose 
sugar, one phosphate group and one nitrogenous group
Purines- adenine and guanine have a two-ring nitrogenous base structure 
(Pure as gold)
Pyrimidines- cytosine and thymine/uracil have a single-ring nitrogenous base
structure
Anti-parallelism- the opposing orientation of the two nucleotide chains in a 
DNA molecule
Complementary base pairs- specific purine-pyrimidine pairs
Histones-DNA coil around these proteins forming structures that resemble 
beads on string
Nucleosome- a DNA “bead” 
Chromatin- 
DNA Replication
Semiconservative- the process discovered by Watson and Crick in which a 
double helix can unwind to form two identical double helix structures
Replication occurs during the S phase of the cell cycle Replication Fork- hydrogen bonds break and the DNA unwinds and two 
identical chains are built in a fashion that resembles a fork
DNA polymerase- major replication enzyme
Polymerase chain reaction-uses DNA polymerase to rapidly replicate a 
specific DNA sequence in a test tube and requires the following
1. Knowing a target DNA sequence from the suspected pathogen
2. Two complimentary in sequence primers
3. Many copies of the 4 nucleotides

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School: University of Connecticut
Department: Biology
Course: Human Genetics
Professor: Colleen Spurling
Term: Fall 2015
Tags:
Name: Chapter 9 DNA Structure (updated)
Description: this updated set of notes now contains information from Week 1's lecture
Uploaded: 01/18/2018
8 Pages 22 Views 17 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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