Nucleic Acids Lab Biology- Chapter 10 Honors Biology- Chapter 9
Jan 19, 2016
Nucleic Acids
Lab Biology- Chapter 10Honors Biology- Chapter 9
Found on chromosomes Segment of DNA Codes for a trait
Gene
Characteristic due to a single gene or multiple genes
Eye color
Hair color
Blood type
What is a trait?
Deoxyribose sugar
Phosphate group
Nitrogen containing base◦ Four possible bases
Structure of DNA
2 rings of carbon and nitrogen
Adenine
Guanine
Purines
1 ring of carbon and nitrogen atoms
Thymine
Cytosine
Pyrimidines
DNA is composed of 2 nucleotide chains
Nucleotides connected through covalent bonds
The Double Helix
Each strand has a 5’ and a 3’ end
Each strand runs in an opposite (antiparallel) direction
Antiparallel
Nucleotide linkage
Covalent bonds
between sugar
and phosphate
molecules
Forms a sugar-
phosphate
backbone
Honors
5’
3’
Covalent bond Chemical bonding through sharing of
electron pairs
Honors
Purine Pyrimidine A T – 2 Hydrogen bonds C G – 3 Hydrogen bonds
Complementary Base Pairing
Hydrogen bonding between base pairs Hydrogen atom - electronegative atom
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Hydrogen bonds? Covalent bonds?
Chargaff’s rule The DNA of any given species contains
◦adenine = thymine ◦guanine = cytosine
Honors
Wilkins and Franklin Used X-ray diffraction
◦ A picture of how X-rays bounced off a DNA molecule
Discovering the double helix model
FranklinWilkinsX-ray diffraction
X-Ray diffraction Used to determine arrangement of atoms
within a crystal structure Distance between dark spots- distance
between turns of the helix
Honors
Performed no physical experiments on DNA Spent a lot of time thinking about DNA Focused on creating a model that fit with
the data
Watson and Crick
Wilkins, Watson, and Crick received the Nobel Prize in 1962
Franklin died in 1958 and was not recognized
Nobel Prize cannot be awarded posthumously
Nobel Prize
Write a two paragraph reflection on Rosalind Franklin. ◦ One paragraph should detail her contribution to
the discovery of the structure of DNA. ◦ Second paragraph should state your answer to
the questions: Do you think Franklin deserved the Nobel Prize? Why do you think she did not receive more
recognition? ◦ Evidence must be provided to support your
opinions. ◦ Complete this assignment on loose leaf paper.
Homework
Occurs in all living organism Takes place in the nucleus One double stranded
molecule two identical copies
DNA Replication
Original strand
New strand
Helicase (enzyme) holds the two strands
apart
◦ Break hydrogen bonds between bases
Step 1: Replication Fork
Replicates simultaneously
Honors
DNA polymerase synthesizes DNA by adding nucleotides in a 5’ 3’ direction
Leading strand- continuous◦ Moves in the direction of unwinding
Lagging strand- discontinuous
Step 2: DNA Polymerase
Lagging Strand Discontinuous Forms in the opposite direction of replication fork Creates Okazaki fragments Must wait for a new primer to be placed
Honors
DNA Primase- lays down short segments of RNA primer
DNA Polymerase III- adds new nucleotides DNA ligase- bonds Okazaki fragments
together
Honors
Semiconservative model
Honors
What happens when DNA Polymerase makes a mistake?
Mutation- Change in nucleotide sequence
Can be repaired through DNA repair mechanisms
Mutations
One nucleotide is substituted for another Sickle Cell Anemia
Substitution
A nucleotide is deleted Cystic fibrosis
◦ Deletion of "AT" from the sequence "ATAT" in the CFTR gene
Causes a frameshift
Deletion
A nucleotide is added
Huntington’s disease
Causes a frameshift
Insertion
DNA segment is
broken and flipped
No frameshift
No loss of genetic
information
Different order
Hemophilia
Inversion
Part of the gene is moved◦ Either moved on the same chromosome or moved
to a different chromosome A form of Down syndrome Part of Chromosome 21 is moved to
Chromosome 14
Translocation
DNA Replication Game http://www.nobelprize.org/educational/medi
cine/dna_double_helix/dnahelix.html Honors: DNA Replication http://
www.wiley.com/college/pratt/0471393878/student/animations/dna_replication/index.html
DNA Replication: http://www.mcb.harvard.edu/losick/images/t
rombonefinald.swf
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