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Pre-AP Biology DNA and Biotechnology Study Guide
Structure of DNA:
Number of strands _____________. Parallel or antiparallel? _______________. Rosalind
Franklin’s x-ray crystallography image indicated that the 3-D shape of the molecule was
_____________. Chargaff’s ratios indicated that there is complementary base pairing: A with
____ and C with ____. If the amount of A in a species DNA is 30%, the amount of T is ____, C is
____ and G is _____. The bonds between the bases (A, T, C and G) are _______. While the
bonds between nucleotides (between the sugar and phosphates of the backbone) are _______.
__________ and ________ were the first to build and publish an accurate model of the DNA
molecule. Add labels to the diagram: sugar, phosphate, A, T, C, G, H-bonds, covalent bonds.
Structure of nucleotide:
Describe the relationship of the nucleotide to DNA (include the vocabulary terms monomer and
polymer) ______________________________________________________________
Label the three components (A, B, and C) that make up the nucleotide
Meselson Stahl experiment:
According the Meselson Stahl experiment, DNA replication is: _______________
Draw a picture model of the Meselson Stahl experiment findings. Include: light versus dark nucleotides (difference in
shading), the initial DNA molecule and the two molecules that result after replication has been completed.
What percentage of the original nucleotides would be remaining after 1 round of replication: _____ after 2 rounds: ___
after 3 rounds: ____
after 4 rounds: _____. Describe and explain this pattern:
DNA replication:
Which enzyme is responsible for unwinding the double-helix? _____________________________
Which enzyme is responsible for building each complementary new strand using the original strands as a template?
____________________________________
How does this enzyme know which bases to add to the growing new strands of DNA? ____________________________
Describe three times (reasons) that a cell would need to replicate its DNA: _____________________________________
When, in the cell-cycle, is DNA replicated? _______________________________________________________________
Compare/contrast DNA and RNA:
Comparison
Name of sugar
List of nucleotides
Number of strands
Where found in the cell
Types of
DNA
RNA
Transcription and Translation:
Describe the central dogma of biology
(flow of genetic information):
What is transcription?
Where in the cell does it occur?
What is translation?
Where in the cell does it occur?
Describe how different types of RNA
interact during transcription:
Mutations:
What are mutations and how do they occur?
What is the significance of mutations to evolution?
What is a silent mutation? Explain why some mutations are silent. What is the significance of this?
Describe what a frame-shift mutation is. Why is this type of mutation have a particularly large impact on the protein
product? What is the difference between a frame-shift mutation at the start versus end of a gene?
What type of mutation produced the sickle-cell allele? How does it affect hemoglobin protein? Was this mutation
positive, negative, or neutral? Explain:
Polymerase Chain Reaction (PCR):
Why is PCR used by researchers?
Describe how PCR works?
Restriction enzymes:
Where do restriction enzymes come from and what do they do?
Describe two separate uses of restriction enzymes in biomedical research:
Show how the DNA below is cut by EcoRI, which recognizes the sequence GAATTC and cuts between the G and A:
How many cuts would be made? How many fragments of DNA would result? What would be the size (base-pairs)?
Gel electrophoresis:
Why is DNA loaded in the wells at the side of the gel box with the negative electrode?
Draw the DNA fingerprint for
the DNA sample to the left.
What is recombinant DNA and how is it created and describe on use of this
technology:
Pre-AP Biology DNA and Biotechnology Study Guide
Structure of DNA:
Number of strands _2- double___. Parallel or antiparallel? __antiparallel____. Rosalind
Franklin’s x-ray crystallography image indicated that the 3-D shape of the molecule was
__helical_. Chargaff’s ratios indicated that there is complementary base pairing: A with _T_
and C with G_. If the amount of A in a species DNA is 30%, the amount of T is 30%, C is _20%
and G is 20%_. The bonds between the bases (A, T, C and G) are _hydrogen_. While the bonds
between nucleotides (between the sugar and phosphates of the backbone) are _covalent_.
Watson and Crick were the first to build and publish an accurate model of the DNA molecule.
Add labels to the diagram: sugar (5), phosphate (6), A (3), T (4), H-bonds (1), covalent bonds (2).
Structure of nucleotide:
Describe the relationship of the nucleotide to DNA (include the vocabulary terms monomer and
polymer) ___nucleotides are the monomers of the polymer called DNA____
A is the phosphate group, B is the sugar (deoxyribose for DNA) and C is the nitrogenous base
Meselson Stahl experiment:
According the Meselson Stahl experiment, DNA replication is: _____semi-conservative______
Draw a picture model of the Meselson Stahl experiment findings. Include: light versus dark nucleotides (difference in
shading), the initial DNA molecule and the two molecules that result after replication has been completed.
Each side of the original DNA molecule serves as a template and new nucleotides are
added based on base-pairing rules (A bonds with T and C bond with G). Half of each
molecule is composed of the original nucleotides (dark) and half from new nucleotides
(light).
What percentage of the original nucleotides would be remaining after 1 round of replication: _1/2_ after 2 rounds: _1/4
after 3 rounds: _1/8_ after 4 rounds: _1/16_. Describe and explain this pattern: The pattern is exponential decay,
reduced each round by ½ of the previous because of the semi-conservative nature of DNA replication.
DNA replication:
Which enzyme is responsible for unwinding the double-helix? ___helicase_____
Which enzyme is responsible for building each complementary new strand using the original strands as a template?
_____DNA polymerase________
How does this enzyme know which bases to add to the growing new strands of DNA? base-pair rules (A w. T and C w. G)
Describe three times (reasons) that a cell would need to replicate its DNA: growth, replacement, reproduction
When, in the cell-cycle is DNA replicated? S-phase (S stands for DNA synthesis)
Compare/contrast DNA and RNA:
Comparison
Name of sugar
List of nucleotides
Number of strands
Where found in the cell
Types of
DNA
deoxyribose
A, T, C, G
2
nucleus
Nuclear, mitochondrial
RNA
Ribose
A, U, C, G
1
Nucleus, cytoplasm
mRNA, tRNA, rRNA
Transcription and Translation:
Central dogma: DNA →mRNA →protein. Transcription is the
copying of the information stored in the DNA molecule of a
gene into a mRNA molecule and this occurs in the nucleus.
Translation occurs in the cytoplasm or on the E.R. on a
ribosome and involves tRNA molecules bringing amino acids
in the correct order (because each tRNA anticodon
corresponds to a mRNA codon) to translate the code of mRNA
nucleotides into a polypeptide (protein).
Mutations:
A mutation is a random change in DNA code that occurs during DNA replication or through a failure in repair
mechanisms. The significance is that mutation is the primary source of genetic diversity – it is how we get brand new
alleles. Genetic diversity is necessary for evolution through natural selection. Some mutations are silent (no change in
amino acid) because of redundancy in the codons (64 codons for 20 amino acids) as a result many mutations do not
affect the protein product. A frame-shift mutation results from the addition or deletion of one or two nucleotides,
thereby shifting the reading-frame and changing all amino acids downstream. As a result, the earlier this occurs in a
gene, the larger the impact. A simple substitution mutation (A→T) resulted in the sickle-cell allele. The resulting
hemoglobin protein clumps together into long rods, which distort the shape of red-blood cells. Being heterozygous is an
advantage in malarial-zones because it confers partial resistance to malaria. No advantage where there is no malaria.
Polymerase Chain Reaction (PCR):
PCR quickly amplifies (makes many copies) of DNA. It uses a heat-stable DNA polymerase enzyme (taq polymerase) from
a thermophilic bacterium and alternate heating and cooling cycles.
Restriction enzymes:
Restriction enzymes come from bacteria; bacteria use them protect themselves from viruses because the enzymes chop
up viral DNA. Researchers use them to cut DNA into fragments to create DNA fingerprints in gel electrophoresis and to
insert foreign genes when making recombinant DNA
Two cuts by EcoRI (GAATTC), resulting in three fragments with the following sizes in base-pairs (from left to right): 11, 5,
and 5.
Gel electrophoresis:
DNA is loaded at the negative side because DNA is negatively charged and would thus be repelled and travel through the
gel towards the positive electrode.
Recombinant DNA is DNA that is a combination of DNA from more than one
organism. It is created by cutting both pieces of DNA with the same restriction
enzyme. The sticky-ends will have complementary base-pairs, allowing the two
pieces of DNA to connect together. DNA ligase solidifies the bonds. The
human gene for insulin has been inserted into bacteria and today bacteria
manufacture human insulin for those with diabetes.