Unit 5 Flashcards
watson and crick
discovered the double helix and twisted ladder structure of DNA
T.H. Morgan
discovered that genes are located on chromosomes and the two components of chromosomes, DNA and proteins,
Griffith
discovered the transforming of principle. He worked with mice and found transforming principles
Avery
purified DNA by expanding on Griffiths work (his experiments gave DNA more weight for being genetic material)
Hershey and Chase
worked with viruses (Bacteriophages) and further supported DNA, was responsible for genetic material
Chargaff
discovered base pairing rules
(A=T, C=G)
Franklin and Wilkins
used x-ray images which suggested that the DNA was made up of two strands forming a double helix
these images were used by Watson and Crick to determine the overall structure of DNA
double helix structure
structure of DNA
2 linked strands that go around each other to resemble a twisted ladder
nucleotide
the monomer of DNA
made up of three components: phosphate, sugar, base
there molecules bonded together creates 1 nucleotide
pyrimidines
bases have a single ring as their structure
bases include cytosine, thymine, and uracil
purines
bases have two rings as their structure
bases include guanine and adenine
antiparallel- 5’ and 3’
opposite orientations of the two strands of DNA- the 5’ end of one strand aligns with the 3’ end of the other strand
5’ end always has a phosphate
3’ end always has a sugar
base pairing rules
A always pairs with T (vice versa)
C always pairs with G (vice versa)
be able to do math problems on this
semiconservative model of DNA
each molecule of DNA consists of one old (original) strand of DNA and one new strand that was created during DNA replication
DNA Replication diagram
know what is what on the diagram we made and the steps
helicase
unzips DNA molecule to access Nitrogen bases
#1 on diagram
Single-stranded binding proteins
binds to the single strands of DNA and stabilizes it
keeps DNA apart to allow replication to occur
#3 on diagram
Topoisomerase
binds ahead of the helicase to relieve strain on whole DNA molecule (does this by breaking bonds in backbone of DNA)
#2 on diagram
DNA polymerase 3
finds primers to begin adding nucleotides to the new strand (by adding dATP); builder
#5 on diagram
DNA polymerase 1
finds primers and cuts the RNA primers off and replaces it with DNA bases
#8 on diagram
primase
lays primer; acts like a flag to let DNA polymerase 3 know where to bind/build
#4 on diagram
primers
5-10 inch long RNA fragments that lay down the foundation for DNA synthesis; it allows DNA polymerase 3 to bind to the DNA strand
Dark pink on diagram
ligase
takes the Okazaki fragments, once primers have been removed and glues them together
#9 on diagram
leading strand
5’ to 3’
is built continuously due to the fact DNA polymerase can only build on the 3’ end
starts with a phosphate
top strand on diagram at the bottom and is #1 on the diagram to the side
lagging strand
3’ to 5’
is built in short fragments because DNA polymerase can only add to the 3’ end. therefore it is working backwards
starts with a sugar
bottom strand on diagram at bottom and #2 on the diagram to the side
Okazaki fragments
short fragments of DNA on the lagging strand that will be glued together
proofreading
all of DNA polymerase proofreads; during DNA replication the DNA polymerase can “check their work” with each base that they add
direction of new synthesis and why?
DNA is synthesized in the 5’-3’ direction
Due to the fact that nucleotides are added only to the 3’ end of the growing strand… this is because DNA polymerase can ONLY work in the 5’-3’ direction and can only add bases to 3’ end
origin of replication
where the two DNA strands are separated, opening up a replication “bubble”
replication fork
a Y-shaped region where the parental strands of DNA are being unwound
dATP
a molecule that is used to build the new strand of DNA, dATP has three phosphates, a ribose sugar and a nitrogen base. This molecule will break two phosphates off and use the energy that is released by the breaking of the bonds to bind the new nucleotide (phosphate, deoxyribose sugar, nitrogen base) to the new DNA strand
nucleotide excision repair
more than 1 base pair needs to be fixed, a nuclease cuts out and replaces damaged stretches of DNA
STEPS: nuclease cuts out damaged DNA, DNA polymerase rebuilds, ligase glues it down
excision repair is a process that is only successful when all three steps are completed
nuclease
cuts out and replaces damaged stretches of DNA
nucleoid
contains genetic material of the prokaryotic cell
telomeres
eukaryotic chromosomal DNA molecule have special nucleotide sequences at their ends called telomeres
they are noncoding regions of the DNA on the end of chromosomes
does not shot the shortening of DNA molecules but does post pone the loss of genetic information (everytime DNA is replicated it becomes shorter)
telomerase
An enzyme that catalyzes the lengthening of telomeres in eukaryotic germ cells
not active in most human somatic cells; however, it does show inappropriate activity in some cancer cells and understudy as a target for cancer therapies
chromatin
proteins (histones) plus DNA… it is the essence of a chromatid
histones
proteins responsible for wrapping the DNA to form a chromatid
what types of bonds are between bases
hydrogen bonds
how many bonds between G and C
3 hydrogen bonds
what types of bonds are in the backbone of DNA
covalent bonds
what two molecules make up the backbone of DNA
alternates with sugar (deoxyribose) and phosphate
how many bonds between A and T
2 hydrogen bonds
