Define Transformation.
a process where some bacteria take up foreign genetic material (naked DNA) from the environment
Define Bacteriophage.
a kind of virus that infects bacteria, composed of DNA/RNA cores and a protein coat
Define Nucleotide.
a compound made of a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base
4 types of nitrogenous bases: Adenine, Thymine, Guanine, Cytosine
Define Base Pairing.
the principle that states that adenine and thymine pair together, and cytosine and guanine pair together in DNA strands
Define Histones.
proteins
Define Nucleosomes.
a DNA-histone complex which makes bead-like structure (unit of chromatin)
Define Chromatin.
made of nucleosomes (DNA coiled around protein) packed together in eukaryotes to make the chromosome
Define Supercoils.
a thick rope-like structure created by nucleosome coils
Define Replication.
the copying process in which a cell duplicates its DNA before dividing, ensuring each resulting cell has a complete set of DNA molecules
Define DNA Polymerase.
the principal enzyme involved in DNA replication
What are Purines?
Adenine and Guanine
What are Pyrimidines?
Cytosine and Thymine
Define Leading Strand Properties.
- RNA Primase makes primer, which creates a starting point.
- DNA polymerase continuously adds nucleotides from that point forward towards the replication fork
- 5’-3’ direction
Define Lagging Strand Properties.
- RNA Primase makes primer, DNA polymerase starts working backwards on the strand (away from replication fork).
- The strands are synthesized in short bursts, called Okazaki fragments.
- Another kind of DNA polymerase has to go back and replace RNA primers.
- DNA ligase comes around and joins the bases together.
- 3’-5’ direction
Explain Griffiths’ Experiment.
- Frederick Griffith wanted to learn how bacteria produce pneumonia. He tested two strains on mice, and both grew well, but only one caused pneumonia.
Conclusions:
- A chemical substance from one cell is chemically transforming another cell. (Something from the dead, boiled, lethal bacteria changed the harmless bacteria)
Explain Averys’ Experiment.
- Repeated Griffith’s experiment, using enzymes that destroyed proteins, lipids, carbs, and RNA, but transformation still happened. When they finally did it with DNA, transformation stopped happening.
- Conclusions:
1. Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next.
2. DNA is the transforming factor.
Explain Hershey-Chases’ Experiment.
- Alfred Hershey and Martha Chase studied viruses, and found that whatever the bacteriophage was injecting inside the bacteria was the genetic material. Thus, they coated the virus’ DNA in phosphorus-32 (radioactive isotope) and the protein in sulfur-35 (radioactive isotope).
- Conclusions:
1. They found phosphorus-32 inside the bacteria and concluded that the genetic material of the bacteriophage was DNA, not protein.
2. Genes are made up of DNA.
Explain Chargaffs’ Rules.
- Erwin Chargaff found that cytosine and guanine percentages were equal in DNA samples, just as adenine and thymine balanced each other out in the same way.
- Conclusions:
C and G come in the same amounts.
A and T come in the same amounts.
C + G is NOT equal to A+ T
Explain Rosalind Franklins’ Experiment.
- Used x-ray diffraction, stretching DNA fibers to make the strands parallel and aiming x-ray beams at the sample. She recorded the scattering pattern and made the famous photo 51.
- The x-shape in the picture indicated 2 strands in the structure and nitrogenous bases begin towards the center.
Explain Watson and Cricks’ Experiment.
Watson saw Rosalind Franklin’s photo 51 and within a few weeks, he and Crick made a 3D model with 2 strands in a double helix which was published in a one-page paper.
