DNA Replication Notes Flashcards
Nuclear Chromosomes/Eukaryotic DNA
Have a linear structure • Compacted by interaction with proteins • Many hundreds or thousands of genes each
Different forms of DNA
- Nuclear Chromosomes/Eukaryotic DNA
-Mitochondrial Chromosomes/Prokaryotic
DNA
Mitochondrial Chromosomes/Prokaryotic
DNA
Circular DNA molecule • Not compacted with protein • Similar to prokaryotic chromosomes • Reflects evolutionary history of mitochondria • Not many genes (37 in humans)
Deoxyribonucleic Acid
Controls production of proteins within cell
Chromatin
DNA is never found alone!, it is a complex association of DNA and proteinthat makes up chromosomes in nondividing cells
Chromosomes
Tightly wound chromatin
Chromatid: one of two identical parts of a
chromosome - occurs during cell division.
Histones
DNA-binding proteins that assist
in compacting and folding DNA into a
chromosome.
Nucleosomes
Bead-like structures composed of histones wrapped with DNA.
Structure pf DNA is related to function. What are the functions of DNA
- Store and use information to direct cell activities
- Copy ITSELF EXACTLY for new cells
What parts is DNA made of
Polymer made of monomers called nucleotides. Each nucleotide is made of 3 parts 1. 5-Carbon Sugar (Deoxyribose) 2. Phosphate 3. Nitrogen Base
DNA (twisty) structure
DNA molecule forms double helix (twisted ladder shape)
Sugar and Phosphate alternate to make up side or backbone of
ladder
-Held together by a sugar-phosphate bond called a phosphodiester bond
Base Pairs make up rungs of ladder
-Hydrogen bonds hold the bases together
Sugar in backbone is bonded to the nitrogen base of the rung
-Covalent bond holds the sugar and base together
What are the nucleotide bases for DNA
- Adenine
- Guanine
- Cytosine
- Thymine
Purines
- Double ring of C and N
- Adenine and Guanine
Pyrimidines
- Single ring of C and N
- Thymine and Cytosine
How do nucleotide bases pair
A purine always pairs with a pyrimidine, to keep all rungs equal A-T G-C - The strands are complementary because of A-T and G-C
DNA scientists
- Miescher 1860
- Frederick Griffith 1928
- Avery, Macleod & McCarty 1944
- Hershey-Chase 1952
- Chargaff 1949
- Rosaline Franklin and Maurice Wilkins 1953
- Watson and Crick 1953
Miecher
-DNA first isolated (called it
nuclein) from cells in 1860’s by
Friedrich Miescher
-shown to contain C, H, O, N and P
-it wasn’t until the 1940’s and 1950’s
that DNA was shown to be the genetic
material
Frederick Griffith
Studying how bacteria caused pneumonia – believed proteins, NOT DNA, were units of heredity. – Determined some factor was being transmitted from non-living bacteria to living bacteria
1944: Oswald Avery
designed an
experiment to further test Griffith’s
findings
-Avery concluded genes are made of DNA
Hershey and Chase
Used viruses called bacteriophages to confirm that DNA is the genetic material
Chargaff
Determined the Base Pair Composition of DNA through analysis of data
Rosalind Franklin and Maurice Wilkins
Used a technique called X-ray diffraction (crystallography)
to study DNA
– These pictures suggested a highly coiled helix
James Watson and Francis Crick
-Develop the double-helix model of the structure of DNA
-To construct this model, they use information about
bonding, Chargaff’s rules, pictures from x-ray
diffraction
DNA replication Helicase
- 1st thing that happens
-“unzips” ladder by breaking
hydrogen bonds
point at which two strands
separate is called the
“Replication Fork”
Multiple replication forks form
along DNA strand
DNA Polymerase
-2nd thing that happens
-Holds two strands apart
-Assembles and proofreads
strands
-Free-floating nucleotides
join unpaired bases on the
2 single strands with help
of DNA Polymerase and
Primase.
-DNA moves 5’ to 3’ and when 3’ to 5’ its okazaki fragments
DNA Ligase
-3rd thing that happens
-Uses ATP as an energy source to seal copies
together
DNA replication accuratcy
- Replication is extremely accurate: 1 error
per 1 Billion nucleotides - DNA is able to repair damage from heat,
radiation, and chemicals - There are many enzymes that help with
accuracy and DNA repair
PCR
Polymerase Chain Reaction: Allows a short
strand of DNA to be amplified about a
million fold
