Lecture 2 Flashcards
What identifies chromosomes as the carriers of genes?
Chromosome theory of inheritance and Mendel’s studies
Why are proteins more complex?
Because proteins have 20 amino acids
What are chromosomes made of?
Proteins and DNA
What did Fred Griffith study?
Pneumonia
What does Streptococcus pneumonia form?
A diplococcus where a pair of cells remain attached due to incomplete cell division
What changed in Griffiths experiment?
Rough looking colonies of diplococcus
What is the characteristics of the Smooth strain of of Pneumonia?
- Smooth colonies form pneumonia
- Kill mice
- glycocalyx protects bacteria from mouse immune system
What are the characteristics of the Rough strain of Pneumonia?
- Rough colonies do not cause pneumonia
- not virulent because they lack the protective glycocalyx
- Look rough because they look glycocalyx
What is Griffiths experiment killed the mice?
The S-strain and the heat killed S strain combined with the R strain
what was the conclusion of Griffiths experiment?
That there was something in the heat inactivated S-cell bacteria that was taken up by the R strain that restored the virulence to the R strain that now looked like the S strain. This is called the transforming principle
What does DNA competence?
It means that a cell has the right facilities to accommodate the DNA
How can researches change bacteria in the lab?
A researcher can modify the bacteria to be competent by adding receptors and then add DNA
How did Avery figure out what was responsible for the transforming principle?
He destroyed different parts of the bacteria and repeated the experiment
What substance is responsible for the transforming principle?
DNA
How does Bacteria replicate?
Bacteriophages injects itself in the bacteria and replicate which produces more bacteriophages
How did Hershy and Chase confirm the transforming principle?
By marking the DNA is phages before they infect bacterium and seeing which one was injected inter the bacteria
what are the things that DNA must be able to do if it is the hereditary material?
Replicate
Carry information
Control cell activity
Mutate
What are the components of DNA?
Nucleotide
What are the components of a nucleotide?
A phosphate group
A pentose sugar
A nitrogenous base
What are the two types of Nitrogenous bases?
Purines (double ring)
Pyrimidines (single ring)
Which Nucleotides are Purines?
Adenine
Guanine
Which nucleotides are Pyrimidines?
Thymine
Uracil
Cytosine
What are the two types of sugars in nucleotides?
Ribose and Deoxyribose
How are Nucleotides attached to all its components?
A phosphate group attaches to the 5th carbon on the sugar and the nitrogenous base attaches to the first carbon on the sugar
how are the 5’ end and the 3’ end of two nucleotides joined?
Through a condensation reaction producing water and a covalent bond
What is the charge of the phosphate group?
Negative
How are the sugar groups able to be inverted?
The covalent bond between the nitrogen and the sugar is complete rotatable
Which part of the DNA has inverted orientation?
The sugar phosphate back-bone but not the nucleotides. Meaning that they are upside down
What is responsible for the 5’ 3’ ends of DNA?
The fact that the sugar phosphate backbone that is in opposite directions
What is Strand Directionality based on?
The orientation of sugar molecules
Who discovered the structure of DNA?
Watson and Crick with the help of Rosalind Franklin
What is Helical Pitch?
The distance between two equivalent positions on the double helix
What is the difference between the Minor Groove and the Major Groove?
The size
How wide is the Double Helis?
2nm wide
What is the Double Helix made of?
Two anti parallel nucleotide polymer strands
What connects nucleotides?
Covalent bonds between phosphates and sugars
How many base pairs per a helical turn?
10.4 base pairs
What connects the two base pairs together?
Hydrogen bonds
How does the Conservative model of DNA replication work?
The parental model conducts replication of an entirely new double stranded molecule
How does the Semi-conservative model of DNA replication work?
The new DNA molecules are composed of a parental strand and a daughter strand (new
How does the Dispersive model of DNA replication work?
The two parental strands are distributed randomly between the daughter molecules
What is the Pulse Chase experiment?
Following molecules through a system by marking them with radioactive markers
What was the Meselson-Stahl approach to proving semi-conservative replication?
He marked the DNA with N15 then brought it back to its normal environment where it duplicated so that half of the DNA was N15 and half was N14 (normal) then separated the DNA strands based on their density using caesium chloride in water
How were DNA bands visualized?
By ultraviolet absorption photography. DNA absorbs light at 260nm
