Exam 3 Flashcards
Parts of nucelosides
base and sugar
parts of nucleotides
base, sugar, phosphate
bases
A, C, G, T
Purines are ___ and ___
A and G
Purines have ____ rings and are ____ (size)
two rings, larger
Pyrimidines are _, _, and _
C, U, and T
Pyrimidines have ___ ring(s) structure and are ____ in size
one; smaller
Who discovered a X-ray diffraction pattern from a DNA smear but were unable to identify the structure
Franklin and Wilkins
What was significant about Watson and Crick’s model
postulated a double stranded molecule with an anti-parallel orientation of strands, bases inside
____ pairs to ____ using 3 H bonds
C pairs to G
__ pairs to __ using 2 H bonds
A pairs to T
how many bases per twist; length of each twist
10 base pairs; 3.4 nm per twist
what does Chargaff’s rule state
purines match with pyrimidines by forming hydrogen bonds
Both DNA strands have the same amount of information, why?
The bases in 1 strand are complementary to those in the other strand
Modern Central Dogma
Replication-transcription-translation-modification
DNA strucure, what at 5’ and 3’
Meselson and Stahl
Different suggestions on possible mode of DNA replication
Conservative DNA
heavy and light DNA,
Semiconservative DNA
used in DNA replication
Dispersive DNA
stripe pattern of of heavy and light DNA
Genome
complete cell DNA sequence
genotype
specific DNA sequence
phenotype
Appearance and/or behavior
What are considered large molecules
free-living cells ranging from 583,000 up to 15 billion nucleotides
Shape and ploidy of most prokaryotes
circular and haploid
Nucleoid of E. coli is has multiple loops held by anchoring proteins. Each loop contains _____
supercoiled DNA
positive supercoiling vs negative supercoils
positive: over winding DNA
negative: under winding DNA
Helicase
Placed at each end of origin by loader and moves in each direction to copy genome by “melting DNA”
“unwinding enzyme”
What enzyme requires free 3’ OH
DNA polyermase
Primase
Begins replication by making a free 3’OH for DNA polymerase
Who is associated with Nuclein in 1869
Miescher
Transformation in 1928
Griffith
Transformation 1944
Avery, MacLeod, McCarty
Blender experiment 1944
Hershey and Chase
The “rules” in 1948
Chargaff
What relieves torsional stress causes by supercoils?
Type I Topoisomerases
What introduces negative supercoils
Type II Topoisomerases
What introduces positive supercoils
Archaeal topoisomerases
semi-conservative replication: 1: 2: 3: 4: 5:
1: Copies information to complementary strand
2: melt double-stranded DNA
3: polymerize new strand
4: DNA opened at oriC
5: polymerization follows bi-directionally around chromosome
What is the order of events for DNA replication?
1: DNA Helicase unwinds the DNA
2: Primase makes a free 3’OH avaialbe
3: DNA polymerase uses free 3’OH and clamp binds DNA polymerase III to strand
4: Polymerase proceeds 5’ to 3’ on each strand with energy for polymerization coming from phosphate groups on the recently added nucleotide
5: Gaps filled in by DNA polymerase I
Ligase seals nicks
Replisomes are _____, so DNA is threaded through the replisomes
stationary
Extrachromosomal pieces of DNA
Plasmids
What are the two types of plasmids and how many copies of plasmids are there per cell for each
Low-copy-number: one or two copies per cell
High-copy-number: up to 500 copies per cell that divide continuously and randomly segregate
Plasmid replication is similar to chromosomal replication since they both are _______ replication
Bidirectional
Plasmid replication can occur _____, like chromosomal replication or _____
Bidirectionally; unidirectional
