18.1 DNA Structure and Replication Flashcards
Who coined the term Nucleic Acid?
Friedrich Meischer
What is DNA (deoxyribonucleic acid)?
The nucleic molecule that governs the process of heredity in all plant and animal cells
What is Ribonucleic Acid (RNA)?
A nucleic acid that plays a role in gene expression and protein synthesis
What did Levene prove about chromosomes?
That they were made up of DNA and proteins
What experiment did Frederick Griffith conduct?
In order to study the bacteria responsible for pneumonia, he injected live and non-live bacteria into mice
What were the results of Frederick Griffith’s experiment?
The dead pathogenic bacteria some had somehow passed on their disease-causing properties to live, non-pathogenic bacteria
What is the Transforming Principle?
Discovered y Frederick, the ability of dead pathogenic bacteria to pass on their disease-causing properties to live, non-pathogenic bacteria
What provided evidence that DNA played a role in the transformation principle?
When they treated the heat-killed pathogenic bacteria with a protein destroying agent, the transformation still occurred. When they treated the heat-killed pathogenic bacteria with a DNA destroying agent, the transformation did not occur
How did Martha Clause show that genes are made of DNA?
She used a virus that consists of a protein coat surrounding the length of DNA. The virus injects its genetic information in the cell. They labelled the protein coat using radioactive sulfur and the DNA with radioactive phosphorus. It then showed that Viral DNA and not viral protein enters the cell
What are Nucleotides?
The individual units that make up the long chains of DNA and RNA
What is each DNA Nucleotide composed?
A five carbon sugar, a phosphate group, and one of the 5 nitrogen containing bases
What are the 4 nitrogen containing bases found in DNA nucleotides?
Guanine
Cytosine
Adenine
Thymine
What nitrogen containing base does RNA nucleotides contain?
Uracil (U) instead of thymine. But the rest are all the same
What are the Nucleic Acids made of?
Long Chains of Nucleotides strung together
What is Chargaff’s rule?
The idea that Guanine and Cytosine are present in equal amounts. And Adenine and Thymine are present in equal amounts
What did Franklin determine about DNA through X-ray photography?
DNA has a helical structure with two regularly repeating patterns
What are the inside and outside portions of DNA made of?
The nitrogenous bases are located on the inside and the sugar phosphate backbone is located on the outside
Who published a paper describing the double helix model?
Watson and Crick
What remains constant in a DNA molecule?
The distance between the sugar phosphate handrail even the nitrogenous bases are different sizes
What are Adenine and Guanine derived from?
A family of compounds known as purines which have a double ring structure
What are Thymine and Cytosine derived from?
Pyrimidines which have a single ring structure
What are the complementary base pairs?
A-T and C-G
What are the complementary base pairs held together by?
Hydrogen Bonds
What does Antiparallel mean in terms of DNA?
The phosphate bridges run in opposite directions in the two strands
Where are DNA and RNA found?
In most bacteria and the Nuclei of most Eukaryotic cells
What are the 3 structural differences between DNA and RNA?
- The sugar component of RNA is ribose rather than deoxyribose
- RNA does not have the nucleotide Thymine, instead it has Uracil
- RNA is single stranded, although a single strand can sometimes fold back on itself to produce regions of complementary base pairs
What is a Gene?
A functional sub-unit of DNA that directs the production of one or more polypeptides (protein molecules)
What is the Genome of an organism?
The sum of all the DNA that is carried in each cell of the organism
What is replication?
The process of creating an exact copy of a molecule of DNA
What does it mean that DNA replication is Semi-conservative?
It means that each new molecule of DNA contains one strand of the original complementary DNA molecule and one new parent strand
What is the Replication Origin?
A specific nucleotide sequence that replication starts at. There can be many spots on a DNA where this occurs
What are Helicases and what do they do?
They are a group of enzymes that bind to DNA at the replication origin creating y shaped areas of separated nucleotides
What is the Replication Bubble?
The opened up, seperated, region of DNA that the Helicase creates
What is the Replication fork?
Two unwound strands of DNA that branch into unpaired (but complementary) single strands
What serves as templates for the new strands of DNA?
The unwound strands of DNA at the replication fork
What does DNA polymerase do?
Inserts into the replication bubble and begins to add nucleotides
What is elongation?
The process of joining nucleotides to extend a new strand of DNA
Where does DNA polymerase attach new nucleotides?
To the free 3’ end of an existing chain
What are the two conditions for elongation?
It can only take place in the 5’ to 3’ direction and a short strand of RNA known as primer must serve as a starting point for the attachment of new nucleotides
What is the RNA primer?
A short strnad that serves as a starting point for the attachment of new nucleotides
What is the Leading strand?
The strand that is replicated continuously in the 5’ to 3’ direction
What is the Lagging strand?
The strand of DNA that is replicated in short segments in the 5’ to 3’ direction
What are Okazaki fragments?
The DNA that gets replicated in the 5’ to 3’ direction but in short segments
What does DNA Ligase do?
Splices together the Okazaki fragments
What is needed to construct the RNA Primer?
An enzyme called Primase
What happens one the Primer is in place?
DNA polymerase extends each fragment by adding new nucleotides and it also removes the RNA primer by eliminating the nucleotides in the 5’ to 3’ direction and fills in the space by extending the neighboring DNA strands
What is another important function of DNA polymerase?
It proofreads by recognizing whether a hydrogen bond is taking place and between the new base and its complement on the original strand. If there is no hydrogen bond, there is a mismatch between bases
What is the replication machine?
The complex of polypeptides and DNA that interact act the replication fork
What is Termination?
The completion of the new DNA strands and the dismantling if the replication machine
What is DNA sequencing?
The process of identifying the precise nucleotide sequence in a DNA fragment
What was the Human Genome Project?
A monumental effort to sequence the entire human Genome
