Final- 16 Flashcards
Who discovered the double helix and when
April 1953
Watson and Crick
Who preformed the blender experiment
Hershey and Chase
What did the blender experiment show
DNA was the genetic material of the phage T2
What tagged the protein
Sulfur
What tagged the DNA
phosphorus
What did Erwin Chargaff do
Developed a series of rules based on a survey of DNA composition in organisms
- composition varies from one species to the next
- Number of A and T is equal to the number of C and G
What was published in 1953
a one page paper by Watson and Crick in Nature reporting their double helix model of DNA
Where replication begins
Origins of replication
What happens when the DNA strands separate
a replication bubble is created
What protein unwinds the strands of DNA
Helicase
Replication fork
Y shaped region where DNA strands are elongating
Single stranded binding proteins
Bind to and stabilize single stranded DNA. Stops DNA from sticking back together
Topoisomerase
Corrects overwinding ahead of replication forks by breaking , swiveling and rejoining DNA strands
RNA primer
Initial nucleotide strand, starting point for replication (5-10 nucleotides) at 3 prime end
Primase
Can start an RNA chain from scratch and adds RNA nucleotides one at a time using parental DNA as a template q
DNA polymerase
Add nucleotides to the 3 prime end (catylize the elongation of DNA at the replication fork)
What end is DNA added to
3 prime
Leading strand
Continuous. Moves towards replication fork
Lagging strand
Discontinuous. Moving away from the replication fork
Okazaki fragments
Laging strand synthesized as series of fragments `
DNA ligase
Joins Okazaki fragments together
What do limitations of DNA polymerase cause
No way to complete the 5 prime ends of the daughter DNA strands
Why do prokaryotic organisms not have a problem with their DNA stands not being completed at the 5 prime end
They have circular DNA molecules
Telomeres
Ends of eukaryotic chromosomal DNA molecules with special nucleotide sequences
What happens to the telomeres at each round of replication
They become shorter. They postpone erosion of genes near ends of DNA molecules
What have eukaryotic cells evolved to do
restore shortened telomeres in germ cells
Telomerase
catalyzes the lengthening of telomeres in eukaryotic germ cells, restoring their original length
Describe bacterial DNA
single, circular, double stranded DNA molecule associated with a small amount of protein
Have a dense region of DNA called a nucleoid
Describe eukaryotic DNA
single, linear DNA double helix that, in humans, has an average of abaout 1.5x10^8 nucelotide pairs
Chromatin
Complex of DNA and protein
fits in nucleus with packaging
Heterochromatin
Condensed chromatin
Euchromatin
More dispersed chromatin. Interphase
What do chemical modifications of histones do
Affect the state of chromatin condensation and affect gene activity
