DNA is Genetic Material
DNA Structure
DNA Packaging
DNA
DNA Replication
100
What are the full names of the scientists behind The Hershey-Chase experiment?
Alfred Hershey and Martha Chase
100
Explain the properties of a DNA nucleotide:
A DNA nucleotide is composed of a molecule of deoxyribose with a phosphate group attached to the 5' (five-prime) carbon and a nitrogenous base attached to the 1' (one-prime) carbon.
100
What are histones, and what process do they help with?
They are a type of protein that helps with DNA packaging.
100
Does DNA only code for proteins?
Less than 2% of human DNA actually codes for proteins or other materials required for protein synthesis.
100
How is DNA provide a way to be copied?
Through the A-T and C-G base pairing.
200
Explain the process behind the Hershey-Chase experiment:
200
What kind of bond is formed between a hydroxyl group 3' carbon of deoxyribose and a phosphate group attached to the 5' carbon of deoxyribose in DNA?
A phosphodiester bond
200
How many histones make up the nucleosome core?
8
200
What is satellite DNA?
Repetitive DNA clustered in discrete areas of a genome.
200
Explain the process of semi-conservative replication, and which two scientists confirmed the theory?
-Each new molecule consists of one newly synthesised strand and one template strand
The two scientists that confimed this theory are Matthew Meselson and Franklin Stahl.
300
Before Hershey and Chase completed their experiment, what did most scientists believe contained the genetic material?
Protein
300
Which end of the DNA strand is a nucleotide attached to? (5' or 3')
3'
300
Why is DNA attracted to histones?
Because DNA is negatively charged and histones are positively charged.
300
Base sequences are carried from the nucleus to what structure, via what type of RNA?
They are carried from the nucleus to the ribosomes via mRNA.
300
Name the two types of "strands" when new DNA is assembled, and explain the difference:
-Leading Strand
-Lagging Strand
The leading strand is continuous, whereas there is a slight delay in the lagging strand and it is discontinous.
400
What did Hershey and Chase conclude after completing their experiment?
DNA, not protein, was the genetic material of the bacteriophage.
400
In the context of DNA strands, what does antiparallel mean?
The two chains run in opposite directions, one strand has the 5' carbon on the top and the 3' carbon on the bottom, the other strand runs the opposite way around.
400
What process do nucleosomes help with?
The supercoiling of DNA
400
Define structural DNA:
Highly coiled DNA that does not have a coding function.
400
Describe how the lagging strand is formed:
1. As the leading strand is synthesized along the lower parental strand the top parental strand becomes exposed. The strand is then recognized by a primase which synthesizes a short RNA primer.
2. DNA polymerase then incorporates a dNMP onto the 3" end of the primer and initiates lagging strand synthesis. The polymerase extends the primer for about 1,000 nucleotides until it comes in contact with the 5' end of the preceding primer. These short segments of RNA/DNA are known as Okazaki fragments.
3. When the DNA polymerase encounters the preceding primer it dissociates. The RNA is then removed by a specialized DNA polymerase or by an enzyme called RNaseH. Ribonucleotides are then excised one at a time in a 5' to 3' direction. The RNaseH leaves a phosphate group at the 5' end of the adjoining DNA segment thus leaving a gap.
4. The gap is filled by a DNA polymerase which uses an Okazaki fragment as a primer.
5. The 3' hydroxyl group on the 3' nucleotide terminus is then covalently joined, using DNA ligase, to the free 5' phosphate of the previously made lagging segment.
500
The bacteriophage acts as a virus within the Hershey-Chase experiment. Explain what happens when a virus infects a cell:
When a virus infects a cell, it takes over the metabolism of the cell, resulting in multiple viruses of its kind being formed.
500
Name all 5 nitrogenous bases, and describe how they pair up:
-Adenine (A)
-Thymine (T)
-Cytosine (C)
-Guanine (G)
Adenine always pairs with thymine, cytosine always pairs with guanine.
500
Explain how supercoiling might occur:
There is often a fifth type of histone attached to the linking string of DNA near each nucleosome, which leads to further packaging of the DNA molecule, and eventually to supercoiled chromosomes.
500
What are polymorphisms?
Polymorphisms are specific regions of DNA that show significant variation between different people.
500
Name 5 enzymes used in the process of DNA replication, and their roles:
-Helicase: Unwinds double helix at replication forks
-Primase: Synthesizes RNA primer
-DNA polymerase III: Synthesizes then new strand by adding nucleotides onto the primer (in a 5' to 3' direction)
-DNA polymerase I: Removes the primer and replaces it with DNA
-DNA ligase: Joins the ends of DNA segments and Okazaki fragments