Cristiano
The first scientist to successfully isolate a DNA molecule and was able to show that the dominant molecule in the nucleus was not protein..
used sperm cells from salmon
Confirmed this nucleus compound: contained Carbon, Nitrogen, and Hydrogen. Rich in Phosphorous Lacked any Sulfur (readily found in proteins)
Friedrich Miescher
Determined the structure of the nucleotide and elucidated how these monomers were linked together. Also established the tetranucleotide hypothesis.
Isolated: The sugars of both DNA and RNA The 4 different nucleotides found in DNA
Phoebus Levene
Utilize an in vivo experiment to provide evidence that transformation occurs.
Studied Streptococcus pneumoniae
Conclusion: • Living ‘R’ bacteria had been transformed into pathogenic ‘S’ bacteria by an unknown, heritable substance from the dead S cells.
Frederick Griffith
Performed an in vitro study to identify DNA as the transforming principle.
Determined: DNA was the material that is transmitted from one generation to the next.
Transformation cannot occur unless DNA is present
Avery, MacLeod, & McCarthy
Analyzed the base composition of DNA in multiple organisms.
2 major findings (known as Chargaff’s rules) 1. Reported that DNA composition varies from one species to another. 2. For each species,
the % of A and T are about equal. (A=T)
The % of G and C are about equal (G=C)
Provided evidence of molecular diversity among species.
Erwin Chargaff
Utilized bacteriophages to provide evidence that DNA is inherited from one generation to the next.
Performed experiments using a phage known as T2
Alfred Hershey and Martha Chase
Developed a method of x-ray diffraction imaging that could detect and visualize DNA, and are responsible for the famous "photo 51".
Franklin concluded that DNA… Was composed of 2 antiparallel sugar-phosphate backbones. Had its nitrogenous bases paired in the molecule’s interior.
Rosalind Franklin & Maurice Wilkins
Interpreted "photo 51" and with chargaff's rules developed a working model of DNA's structure.
James Watson & Francis Crick
An enzyme responsible for breaking the hydrogen bonds between nucleotide base pairs in order to open the replication fork.
helicase
An enzyme that bonds RNA nucleotides to the parent DNA strand in order to provide a primer for a subsequent enzyme.
primase
An enzyme that breaks the bonds attaching the RNA nucleotides of the primer in a 5' to 3' direction and replaces the RNA nucleotides with DNA nucleotides.
DNA Polymerase I
Proteins that bind to the unwound DNA and stabilize it, preventing hydrogen bonds from reforming between the base pairs.
single-stranded binding protein
An enzyme that bonds DNA nucleotides based on complementary base pairing in a 5' to 3' direction.
DNA polymerase III
An enzyme that covalently bonds the 3' end of one fragment of DNA to the 5' end of the neighboring fragment of DNA.
DNA Ligase
An enzyme that breaks a covalent bond in both strands of DNA periodically ahead of the replication fork to prevent supercoiling of the DNA replication.
Topoisomerase
Meselson & Stahl utilized isotopes of nitrogen to determine the method of DNA replication. Based on their results, DNA replication is considered ____________ because the new replicated molecules consist of one original (parent) strand and one new (daughter) strand.
Semi-conservative
You discover a new organism and analyze its DNA. If you find 17% of nucleotides are adenine, what's the percentage of guanine and cytosine
33%
what is the complementary strand for the sequence 5' AAACGCTT 3'
5' AAGCGTTT 3'
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?
DNA polymerase can join new nucleotides only to the 3′ ends of a pre-existing strand, and the strands are antiparallel.
Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. How might adding telomerase affect cellular aging?
Telomerase eliminates telomere shortening and retards aging.
Place the following in order from least condensed to most condensed.
1. 300nm looped domain chromatin.
2. 2nm DNA molecule.
3. 30nm coiled nucleosome chromatin.
4. 1400nm replicated chromosome, only seen during cell division.
5. 10nm DNA wrapped around 8 histones to form nucleosome structures.
6. 700nm condensed chromatin, only seen during cell division.
2, 5, 3, 1, 6, 4
What is the correct order of the steps of DNA replication?
1. New nucleotides are added to the template strand by DNA polymerase III.
2. The DNA helix is unzipped by helicase.
3. Topoisomerase creates nicks in the DNA.
4. Primase adds a RNA primer to the template strand in a 5' to 3' direction.
5. RNA nucleotides are replaced with DNA nucleotides by DNA polymerase I.
6. DNA ligase forms covalent bonds between fragments in the backbone of the newly synthesized DNA strand.
3, 2, 4, 1, 5, 6
A researcher found a method she could use to manipulate and quantify methylation in embryonic cells in culture. In one set of experiments, she succeeded in increasing the acetylation of histone tails in the chromatin of the cells. what would she most likely see in these cells
increase in gene expression
Compared to heterochromatin, euchromatin is...
characterized by having actively expressed genes and comprised of loosely packed nucleosomes.
In Cyanobacteria and plant chloroplasts, what does photosystem II do?
give electrons to the photosynthetic electron transport chain
splits water molecules to generate oxygen gas