01p LECTURE BIMM100 2015.pdf
Transcript of 01p LECTURE BIMM100 2015.pdf
What is Molecular Biology?
“Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology, particularly genetics and biochemistry.” Wikipedia
(from Weaver, “Mol. Biol.”)
Lecture 1 - DNA is the Genetic Material
The molecules of a cell...
“The Central Dogma”
DNA RNA PROTEIN
How do we know that DNA is the genetic material?
VS
MCB, 7th Ed, Figure 1.6
(from Weaver, “Mol. Biol.”)
The Hershey-Chase Experiments, 1952 Phage PROTEIN labeled
Phage
Bacterium
Phage DNA labeled
Bacterium
Phage
What molecule entered the bacterium to
code for more phage?
(from Weaver, “Mol. Biol.”)
DNA/ RNA - chains of nucleic acids Nucleotide: 1. 2. 3. (Note - “nucleoside” is just the pentose + base)
FIG 2-16
DNA/ RNA - chains of nucleic acids
FIG 2-16
RNA bases: A G C U
DNA bases: A G C T
The Bases
FIG 2-17
DNA - 5’ to 3’ directionality
FIG 4-2
The 3-D Structure of DNA
The 3-D Structure of DNA • Franklin’s X-ray diffraction data (1952): DNA is a helix, at least 2 strands
The 3-D Structure of DNA • Chargaff’s rules (1947): #Purines = #Pyrimidines (A = T, G = C BUT A + T = G + C in DNA)
The 3-D Structure of DNA
Nobel Prize for Medicine 1962 - Watson, Crick, Wilkins
• Watson and Crick (1953): model of double helix with purines base-pairing with pyrimidines
strands are antiparallel - opposite 5’ to 3’ directions
~ 10
.1bp
/ 1 tu
rn
FIG 4-3
O
O
H 3’
H 3’
The DNA Double Helix
CH3
Protein-DNA Interactions
• helical DNA has major and minor grooves • atoms at the edges of bases are accessible • proteins can “read” the bases - sequence specific protein binding to DNA • protein binding can bend DNA
-altered structure -regulation of gene expression
TBP binds specific DNA sequences, bends the DNA, enabling transcription
FIG 4-5
• base pairs are complementary • bonds connect the 2 DNA strands • denaturation (melting) • Tm
• How can DNA be denatured?
O
O
H 3’
H 3’
Separation of DNA strands
Detection of DNA denaturation
FIG 4-7
What would happen to the absorption if you took the denatured dsDNA and slowly chilled it on ice?
If 2 samples of genomic DNA have different Tm’s, can they be from the same organism?
Higher GC content = Higher Tm
Why?