18.1 Flashcards
What did Friedrich Miescher coin?
The term “nucleic acid” to determine a weakly acidic, phosphorous contianing base
What is DNA?
A nucleic acid molecule that governs the process of hereditary in all plants and animals
What is RNA?
A nucleic acid molecule that plays a role in gene expression and protein synthesis
What did phobeous lavene show?
That chromosomes are made up of a combination of DNA and proteins
What was griffith experiment?
Studied pathogenic bacteria - used dead S. pneumonia as his control
* Dead pathogenic bacteria passed their disease-causing properties to live non pathogenic bacteria
What happens when heat-killed pathogenic bacteria is treated with a protein destroying enzyme?
Transformation still occurs
What did radioactive labelling prove?
That genes are made of DNA - DNA carried genetic information
What did Hershey and chase use to prove that DNA plays a role in tranformation?
T2 bacteriophage virus
* Injects genetic information into bacterial cell
* Cell manufactures new virus’ and bursts
* Newly release viruses go and affect other cells
- One batch had labelled protein coat with radioactive Sulphur
*Other batch had a labeled DNA using radioactive phosphorous
Cells were blender to separate the viral coats from the bacterial cells - each medium was tested for radioactivity - DNA enters the bacterial cell
What makes up DNA and RNA?
Long chains of individual units - nucleotides
What are the combinations of the four different nucleotides?
A five carbon sugar, a phosphate group, and a nitrogen containing base
What are the four bases in DNA molecules?
Adenine, Cytosine, Thymine, and Guanine
What did Phoebus propose about the proportions of nucleotides?
He proposed that nucleotides were present in equal amounts and these chains repeat in a constant sequence of
* ACTGACTGACTG
Who corrected Phoebus and what did he say?
Griffith - he said that nucleotides are not present in equal amounts - present in varying but characteristic functions
- Adenine is equal to Thymine
- Guanine is equal to Cytosine
What did Rosa Franklin show?
- X ray photography to analyze the structure of DNA
- helical structure with two regularly repeating patterns
She showed that the nitrogenous bases are located on the inside of the helicases - sugar phosphate backbone is located on the outside
What did James Watson and Francis Crick do?
They produced a structural model of DNA that accounts for all experimental evidence
Does the distance between the sugar phosphate remain constant?
Yes
Do the nitrogenous bases differ in size?
Yes
What nitrogenous bases are in the purine family compound?
Adenine and Guanine - two ring structure
What nitrogenous bases are in the pyrimidine family compound?
Thymine and Cytosine - One string structure
What did Watson and Crick determine about how bases bind together?
Adenine binds to Thymine
Guanine binds to Cytosine
Where is DNA and RNA found in prokaryotes?
In the nuclei
How does RNA differ from DNA?
- Single stranded
- RIbose
- Uracil
What is a gene?
A functional sub unit of DNA that directs the production of one or more polypeptides
What is a genome?
The sum of al the DNA that is carried in each cell of an organism
Is there a relation between the number of gene and the genome?
No
What does the speed and accuracy of the replication stage rely on?
- Structural features of DNA
- Specialized proteins
Why is DNA replication semi conservative?
It consists of a new parent said and one complementary strand
What is the replication origin?
The nucleotide sequence that replication starts at
What is the helicases?
Enzymes that bind to the replication origin and unwind the DNA
What is DNA polymerase?
Enzyme that adds nucleotides in the 5’ to 3’ direction - create a strand complementary to existant strand
What is elongation?
Process of joining nucleotides to extend to a new strand of DNA
What are the two conditions for elongation?
- Must go in the 5’ to 3’ direction
- RNA primer must serve as the starting point for the attachment of nucleotides
What is the leading strand?
The strand that is added in the 5’ to 3’ direction
What are okazaki fragments?
Short fragments of DNA that are added in the 5’ to 3’ direction.
What holds okazaki fragments together?
DNA ligase
What reconstructs primer?
Primase
What is a really important job of DNA polymerase?
It proofreads to see if the right bases are paired - if not - parent strand is used as a template
What is the complex polypeptides and DNA that interact at the replication fork?
Replication machine
What is termination?
Completion of the new DNA strands and the dismantling of the replication machine
What is DNA sequencing?
Process of identifying the precise nucleotide sequence of a DNA fragment
