Chapter Three: DNA, RNA Flashcards
Nitrogenous Bases (5)
- Adenine
- Guanine
- Cytosine
- Thymine (DNA)
- Uracil (RNA)
What are the three components of a nucleotide?
- A phosphate group
- A deoxyribose sugar
- A nitrogen-containing base
Purine
Double-ring base
Adenine, guanine
Pyrimidine
Single-ring bases
Cytosine, thymine, uracil
Leading Strand
Strand of DNA moving from the 5’ to 3’ end, named after the numbering of carbons in the deoxyribose sugar.
Lagging Strand
Section of DNA that moves from the 3’ to 5’ direction, named after the numbering of carbons in the deoxyribose sugar.
Fredrich Miescher
Isolated the nuclei of white blood cells and extracted an acidic molecule called nuclein (DNA)
Fredrick Griffith
- Experimented with two strains of bacteria which affected mice. (Pathogenic and non-pathogenic)
- the pathogenic bacteria could cause the non-pathogenic bacteria to also be lethal
- established that either DNA, RNA, or proteins were the material of heredity
Avery, MacLeod, McCarty
- built on Griffith’s work by identifying which molecule was causing the transformation
- subjected the heat-killed pathogenic strain to one of three enzymes: One that killed proteins, DNA, or RNA
- the DNA destroying enzyme did not allow the heat-killed pathogenic strain to become lethal
Hershey and Chase
- T2 bacteriophages tracked by either the 35S isotope (for proteins) or the 32P isotope (for DNA)
- Tracked which isotope was injected into the bacteria from the virus: the 32P
Erwin Chargaff
-studied nucleic acids and their composition
Chargaff’s rule: % composition of A=T, % composition of C=G
Rosalind Franklin
- used x-ray diffraction to analyze DNA samples
- determined DNA’s helical structure, that the hydrogen bonds are on the inside of the molecule, and that the sugar-phosphate backbone is on the outside
Watson and Crick
- worked on a description of the DNA structure:
- “handrail - ladder” illustration
- The distance between the sugar-phosphate backbones remain constant
Semi-conservative Model
DNA replication that results in a hybrid molecule of one new strand and one old strand.
Meselson and Stahl
Proved the semi-conservative model of DNA replication by using nitrogen isotopes to label the old and new DNA during replication.
Replication: Initiation
- Unwinding starts at a specific nucleotide sequence called the origin of replication
- helicase enzymes cleave the hydrogen bonds between bases
- Topoisomerase ll (in prokaryotes) relieves strain on the double helix that is generated from unwinding.
- Replication bubble forms
Replication: Elongation part l
Replication: Elongation part ll
- lagging strand formed in short segments away from replication fork.
- primase synthesizes RNA primer for DNA polymerase lll to extend the strand by creating Okazaki fragments.
- DNA polymerase l removes primers
- DNA ligase joins Okazaki fragments to completer the strand
Replication: Termination
-two new DNA molecules separate from each other, replication fork dismantled
Helicase
Helps unwind the parent DNA
HELI = helix
CASE = break apart
Primase
Synthesizes RNA primer used to generate Okazaki fragments
Single strand-binding proteins
Help stabilize single stranded regions of DNA when it unwinds
Topoisomerase ll
Helps to relieve the strain on the structure of the parent DNA that is generated from the unwinding of the double-helix (in prokaryotes)
DNA polymerase l
- Removes RNA primer and fills gaps between Okazaki fragments
- recognizes and corrects errors in newly synthesized strands of DNA
DNA polymerase ll
Proofreads newly synthesized DNA
DNA polymerase lll
Catalyzes the addition of new nucleotides to the 3’ end of a growing nucleotide strand
DNA Ligase
Joins the ends of Okazaki fragments in the lagging strand synthesis
