Download Daily Slides/Notes

March 15, 2017
Monday, March 13, 2017
LT: I can explain how cell respiration is the process that
provides energy for living organisms.
Entry Task: What macromolecule(s) are
broken down in the:
mouth stomach small intestine Today: Written Test
Continue Ch. 12.1 & 12.2 Reading/Notes
March 15, 2017
Exit Task: What is DNA?
March 15, 2017
Tuesday, March 14, 2017
LT: I can explain the structure and function of DNA.
Entry Task: What is the base pairing rule in
DNA structure?
Today: DNA Extraction Lab
Continue Ch. 12.1 & 12.2 Reading/Notes
March 15, 2017
Exit Task: What kind of bond holds
nucleotides together in a single strand?
What kind of bond holds pairs of nucleotides
together in a double strand?
March 15, 2017
Wednesday, March 15, 2017
LT: I can describe the structure and function of DNA.
Entry Task: What are the 3 roles of DNA in
heredity?
Today:
Ch. 12.1 & 12.2 Reading Quiz
Ch. 12.1 & 12.2 Notes
March 15, 2017
The march to understanding that DNA is the genetic
material
Johann Miescher (1868)
T.H. Morgan (1908)
Frederick Griffith (1928)
Avery, McCarty & MacLeod (1944)
Erwin Chargaff (1947)
Hershey & Chase (1952)
Rosalind Franklin (1952)
Watson & Crick (1953)
Meselson & Stahl (1958)
March 15, 2017
Johann Miescher - 1868
Wanted to identify chemical
composition of nucleus
Isolated acidic compound that
contains nitrogen and phosphorous
March 15, 2017
Genes are on chromosomes 1908/1933
T.H. Morgan
• working with Drosophila (fruit flies)
• genes are on chromosomes
• but is it the protein or the DNA of the
chromosomes that are the genes?
Key factor in determining the
genetic material was choosing
appropriate experimental
organisms (bacteria and
the viruses that infect them)
March 15, 2017
Frederick Griffith - 1928
· Streptococcus pneumonia bacteria
was working to find cure for pneumonia,
worked with pathogenic “S” strain and
harmless “R” strain
· harmless live bacteria mixed with heat-killed infectious bacteria
causes disease in mice
· substance passed from dead bacteria to live bacteria = “Transforming
Factor”
· Transformation: a change in genotype and phenotype due to
assimilation of foreign DNA
March 15, 2017
Transformation?
something in heat-killed bacteria could still transmit disease-causing
properties
March 15, 2017
DNA is the “Transforming Factor” - 1944
Avery, McCarty & MacLeod
· purified both DNA & proteins from Streptococcus pneumonia
bacteria
which will transform live, non-pathogenic bacteria?
· injected protein into bacteria
no effect
· injected DNA into bacteria
transformed harmless bacteria into virulent bacteria
Many biologists remained skeptical, mainly because little was
known about DNA
Conclusion? DNA is the transforming factor!
March 15, 2017
Exit Task: What is true about the relationship
between bases A - T & G - C in any species?
March 15, 2017
Thursday, March 16, 2017
LT: I can describe the structure and
function of DNA.
Say hello to Baby Denman!
His development is brought
to you by DNA:)
Entry Task: How did Avery, et al,
prove that DNA was the
transforming factor?
Today:
Ch. 12.1 & 12.2 Notes
Build a Model of a DNA Molecule
March 15, 2017
Confirmation of DNA - 1952/1969
Hershey & Chase
• classic “blender” experiment
• worked with bacteriophage T2
viruses that infect E.coli bacteria
• grew phage viruses in 2 media, radioactively labeled with either
35S in their proteins
32P in their DNA
• infected bacteria with labeled phages
http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/
0072437316/120076/bio21.swf::Hershey+and+Chase+Experiment
March 15, 2017
Blender experiment
Radioactive phage & bacteria in blender
· 35S phage
radioactive proteins, phage
parts remain suspended in the
liquid therefore protein did
NOT enter bacteria
· 32P phage
radioactive DNA stayed in
pellet therefore DNA did enter
bacteria
· Confirmed DNA is “transforming factor”
March 15, 2017
March 15, 2017
Chargaff - 1947
· DNA composition: “Chargaff’s rules”
varies from species to species
DNA is a polymer of nucleotides
(phosphate, sugar, base)
all 4 bases not in equal quantity
bases present in characteristic ratio
humans:
A = 30.9%
T = 29.4%
G = 19.9%
C = 19.8%
Rules
A=T
C=G
March 15, 2017
Maurice Wilkins and Rosalind Franklin:
X-ray crystallography of DNA
· Showed three things: DNA twisted, double stranded, nitrogen bases
found in middle
· Franklin’s X-ray crystallographic images of DNA enabled Watson/
Crick to deduce that DNA was helical and also the width of the helix
and the spacing of the nitrogenous bases
https://video.search.yahoo.com/video/
play;_ylt=A2KIo9Rr1BdX.xUAZoIsnIlQ;_ylu=X3oDMTByNDY3bGRuBHNlYwNzcgRzbGsDd
mlkBHZ0aWQDBGdwb3MDNQ--?p=Rosalind
+Franklin&vid=0c980bd00567aa840312f814a8724564&turl=http%3A%2F%2Ftse1.mm.bing.net
%2Fth%3Fid%3DOVP.V5d56d607f279436519d23c7d65ef97df%26pid%3D15.1%26h
%3D168%26w%3D300%26c%3D7%26rs%3D1&rurl=https%3A%2F%2Fwww.youtube.com
%2Fwatch%3Fv%3DTZUun93_V18&tit=Rosalind+Franklin+-+My+Favourite
+Scientist&c=4&h=168&w=300&l=296&sigr=11bgb5rgu&sigt=11a6msh04&sigi=1319vjppm&a
ge=1290524777&fr2=p%3As%2Cv%3Av&fr=yhsmozilla-002&hsimp=yhs-002&hspart=mozilla&tt=b
March 15, 2017
Structure of DNA
Watson & Crick - 1953/1962
· developed double helix model of DNA
· Inspired by 3 recent discoveries:
Rosalind Franklin/Wilkins -X-ray
Chargaff’s rules
Linus Pauling – alpha helical structure of
protein
March 15, 2017
DNA Structure
Monomer - nucleotide
Outside - sugar and phosphate backbone - held together by
covalent & phosphodiester bonds
Inside - nitrogen bases (A, T, G, C) - held together by
hydrogen bonds
March 15, 2017
Different Base Pairs
Purines
Nitrogen bases made of
double rings of carbon
and nitrogen atoms
Adenine (A) and
Guanine (G)
March 15, 2017
Different Base Pairs
Pyrimidines
Nitrogen bases
made of single ring
of carbon and
nitrogen atoms
Cytosine (C) and
Thymine (T)
March 15, 2017
Watson and Crick
2 Hydrogen bonds
3 Hydrogen bonds
March 15, 2017
Build a Model of a DNA Molecule
March 15, 2017
Exit Task: In DNA what type of bond(s)
hold the phosphate/sugar backbone
together and what type of bond(s) hold the
nitrogenous bases together?
March 15, 2017
Friday, March 17, 2017
LT: I can describe the structure and
function of DNA.
Entry Task: What is meant by
the term "semi-conservative" replication?
Cool Friday Thing!
Today:
Ch. 12.3 Notes
DNA Replication Assignment
March 15, 2017
Many proteins work together in DNA replication and
repair
· The relationship between structure and function is
manifest in the double helix
· Watson and Crick noted that the specific base pairing
suggested a possible copying mechanism for genetic
instructions
· Since the two strands of DNA are complementary,
each strand acts as a template for building a new
strand in replication
· In DNA replication, the parent molecule unwinds, and
two new daughter strands are built based on basepairing rules
March 15, 2017
Copying DNA
· Replication of DNA
base pairing allows each strand
to serve as a template for a
new strand
March 15, 2017
Semi-conservative replication - 1958
Meselson & Stahl
label “parent” nucleotides in DNA strands with heavy
nitrogen = 15N
label new nucleotides with lighter isotope = 14N
March 15, 2017
DNA Replication
Helicase enzymes break the hydrogen bonds between
base pairs.
March 15, 2017
DNA Replication
The DNA unwinds like a zipper. We call the region
where the separation is occurring the replication fork.
March 15, 2017
DNA Replication
As the DNA separates down the middle, DNA
polymerase recombines adenine with thymine and
guanine with cytosine.
March 15, 2017
DNA Replication
This creates an exact copy
of the original DNA, even
though each strand is
providing a different template.
Semiconservative - each
new DNA molecule
contains one old and one
new strand.
March 15, 2017
DNA Replication
DNA polymerase can only synthesize in one
direction (5′ to 3′), so each strand is replicated
slightly differently.
March 15, 2017
On the leading strand, DNA polymerase simply moves
down the DNA molecule, attaching base pairs as the
DNA continues unwinding. The synthesis of the new
strand is continuous.
Single strand binding proteins have the simple but important function of
preventing the separated strands of DNA from reannealing (rejoining).
March 15, 2017
On the lagging strand, DNA polymerase adds bases in
small segments called Okazaki fragments after
primase adds short RNA sequences called primers.
The synthesis of the new strand is discontinuous.
March 15, 2017
Completing DNA Replication
· Once all of the bases are matched up (A with T, C
with G), an enzyme called exonuclease strips away
the primer(s).
· The gaps where the primer(s) were are then filled by
yet more complementary nucleotides.
· The new strand is proofread to make sure there are
no mistakes in the new DNA sequence.
· Finally, an enzyme called DNA ligase seals up the
sequence of DNA into two continuous double
strands.
https://www.youtube.com/watch?v=wCKF-2nqaOc
March 15, 2017
Replicating the Ends of DNA Molecules
For linear DNA, DNA polymerase cannot
replicate or repair the 5' ends of the daughter
DNA strands.
Result is a shortening of the DNA molecule with
each round of replication.
Telomeres are repetitions (100-1,000) of short
nucleotide sequences at the ends of DNA
molecules that do not contain genes. This
protects the organism's genes from being
eroded.
March 15, 2017