History of DNA Flashcards
Who discovered substance in nuclei
miescher
Who identified components on nucleotides
levene
suggested a transforming factor existed to change bacteria from one strain to another
griffith
Who found that dna is genetic material
Avery-MacLeod-McCarty
Who Confirmed DNA as
genetic material
Hershey-Chase
Who discovered DNA Double helix
model
Franklin, Watson and
Crick
Who discovered
Semi-conservative
DNA replication
Meselson-Stahl
Who Deciphered the Genetic Code
Khorana, Holley, and
Nirenberg
Chromatin
DNA and its associated proteins
Replication origin
site where DNA duplication begins.
Centromere
Holds 2 chromosomes together to make sure each cell will get one copy during cell division
Telomere
Contains repeated nucleotide sequences required for proper replication and protects the ends of the chromosomes
Interphase vs. Mitotic Chromosomes
Mitotic: Two condensed chromosomes.
Interphase: Decondensed DNA
Function of histones
Associate with DNA, forming chromatin and promote chromosomes packing via nucleosomes
What are nucleosomes
composed of histones and DNA held together by noncovalent interactions.
how does histone acetylation affect packing
more acetylation causes less packing, more deacetylation causes more packing.
Heterochromatin vs. Euchromatin
• Heterochromatin: Highly condensed DNA, enriched at
centromeres and telomeres. Contains very few genes,
and those genes contained within heterochromatin are
usually turned off.
• Euchromatin: Less condensed DNA
function of dna helicase
unwinds the double helix, using energy from ATP
Single-strand DNA-binding proteins
stabilize single-stranded DNA
DNA Topoisomerases
Enzymes that allow rotation of the helix to relieve strain during DNA replication. • Prevents tangling of the DNA.
DNA Primase
synthesizes RNA primers for initiation of DNA replication.
• RNA Primers serve as a red flag to ensure extra proofreading of these fragments, provides 3’OH site for DNA synthesis.
Clamp loader
helps load the sliding clamp onto the DNA
DNA Polymerase associates with the clamp
Sliding clamp keeps DNA Polymerase on the DNA until it runs into double stranded DNA and falls off.
Lagging Strand Synthesis
• Synthesis of lagging strand stops when it runs into the 5’ end of another fragment. • RNA primer is degraded. • Sequence filled in by DNA Polymerase.
DNA Ligase
• Enzyme that joins the 3’ end of one fragment to the 5’ end of another Okazaki fragment. • Uses one molecule of ATP to catalyze this otherwise unfavorable sealing reaction.