12.1 - Identifying the Substance of Genes
What was determined to be the substance responsible for transformation in organisms?
DNA
True or False: Maurice Wilkins and James Watson won the Noble Prize for creating the first accurate models of DNA.
False
If a strand reads:
3' A A A T T T C 5'
The matching strand would read...
5' T T T A A A G 3'
The scientist who mistakenly observed DNA while trying to find a vaccine for pneumonia.
Frederick Griffith
Describe the structure of a nucleotide.
There are three parts to a nucleotide - a phosphate, a 5-carbon sugar called deoxyribose, and a nitrogenous base (thymine, adenine, cytosine, or guanine).
The enzyme that unwinds the DNA to prepare for replication
Helicase
The scientist who worked at the Rockefeller Institute in New York and used the process of elimination to discover DNA was responsible for transformation.
Oswald Avery
Describe the importance of Rosalind Franklin's discovery.
Rosalind Franklin used x-ray diffraction to study the structure of DNA. She determined that it was a double helix structure and that the center of the model were nitrogenous bases.
Describe the two things DNA polymerase does.
1. Adds free nucleotides to the unzipped DNA
2. Proofreads the new stands being built to avoid mutations or errors
A team of scientist who used bacteriophages to confirm Avery's data.
Hershey & Chase
Describe the importance of the DNA strands being anti-parallel.
DNA has to be antiparallel. The antiparallel nature allows two strands to go in opposite direction. The antiparallel arrangement of strands allows them to follow Chargaff's rule of base pairing. In this way, nucleotides of one strand are oriented in the center of the molecule, where they bind with their complementary base.
At the end of DNA replication, what would a scientist expects to see?
The scientist will see two identical strands of DNA, both with an original strand and a newly formed strand.
Describe how bacteriophages work.
Bacteriophages are viruses that attack and destroy bacteria. When a bacteriophage enters a bacterium, it attaches to the surface of the bacterial cell and injects its genetic information into it. The viral genes act to produce many new bacteriophages, which gradually destroy the bacterium. When the cell splits open, hundreds of new viruses burst out.
There are two main bonds in a full structure of DNA. Describe them both - what do they bond and discuss their purpose and strength.
Hydrogen Bond is a weak bond found in between the nitrogenous bases. This bond is just strong enough to hold the two strands of DNA together but fairly weak enough to be broken easily during replication.
A covalent bond holds the nucleotides together by bonding together a phosphate and a 5-carbon sugar. This is a strong bond that doesn't allow the strand itself to be broken during replication.
Describe the importance of the enzyme, telomerase.
The tips of chromosomes are known as telomeres. The ends of DNA molecules, located at the telomeres, are particularly difficult to copy. Over time, DNA may actually be lost from telomeres each time a chromosome is replicated. An enzyme called telomerase compensates for this problem by adding short, repeated DNA sequences to telomeres, lengthening the chromosomes slightly and making it less likely that important gene sequences will be lost from the telomeres during replication