DLA #7: Structure and Function of Nucleic Acids Flashcards
DNA and RNA are considered
Nucleic Acids
DNA/RNA are basically a series of ______ linked together by a ______
- Nucleotides
- Phosphodiester Bond
A nucleotide is comprised of
- a phosphate
- a pentose sugar
- a nitogenous base
Phosphates are linked at which carbon of the sugar base
The 5th carbon
The phosphodiester bond links the ____ of one nucleotide to the____ of another
-5’ Phosphate to a 3’ OH
Ribose is found in ______ and dRibose is found in ______
RNA, DNA
What is the chemical difference b/w Ribose and dRibose
dRibose has a H at the 2’
Ribose has a OH at the 2’
Name the two categories of nitrogenous bases
1) Purines
2) Pyrimidines
Give a VERY general description of purine vs pyrimidines and list all that exist
Purines => Double ring structure
- Purine list is:
- 1) Adenine
- 2) Guanine
- Mnemonic: “Pure As Gold
Pyrimidines => Single ring structure
- Pyrimidine list is:
- 1) Cytosine
- 2) Thymine
- 3) Uracil (only in RNA)
- Mnemonic: “CUt The Pye”
The nitrogenous base of a nucleotide is attached at which carbon of the pentose sugar
1’ Carbon
Explain the big difference b/w DNA and RNA when it comes to nitrogenous bases
DNA:
A=T
RNA:
A=U
The hydroxyl group of a nucleotide is found on the
3’ Carbon of the pentose sugar
A nucleoside consists of
- A nitrogenous base
- A sugar group (Ribose/dRibose)
Explain the difference b/w a nucleoside and a nucleotide
Nucleotide => Prescence of phosphate
Nucleoside => No phosphate
Another way of expressing a nucleotide is by calling it
- Nucleoside monophosphate (1 Phosphate)
- Nucleoside diphosphate (2 Phosphate)
- Nucleoside triphosphate (3 Phosphate).
**** A NUCLEOTIDE = NUCLEOSIDE + PHOSPHATE.
**** Popular examples of nucleoside triphosphates include:
- ATP (Adenosine Triphosphate) => Energy
- GTP (Guanosine Triphosphate) => Protein synthesis
- UTP (Uridine Triphosphate) => carrier molecule
Name two enzymes that can catalyse the formation of a phosphodiester bond b/w Nucleotides:
1) Polymerase (DNA/RNA)
2) Ligase (attaches the Okazaki together)
***Okazaki fragments are short segments of DNA
DNA polymerase synthesizes the formation of phosphodiester bonds in what direction
5’ => 3’
When nitogenous bases are being attaches together via a phospodiester linkage, what is the source of energy from this rxn
- Energy is from release of 2Pi (inorganic phosphate)
- Polymerase enzymes catalyzes the binding of nucleotides. Nucleoside triphosphates are brought in, 2 Pi leave, and we are left with a nucleoside mono phosphate.
Topopisomerases/Gyrases have what two types of enzymatic activity
- Ligase activity (“Phosphodiester bond breaker”)
- Exonuclease activity (“Phosphodieser bond sealer”)
What is the ratio of purines vs pyrimidines w/in the DNA:
50/50
How are the two stands of DNA oriented.
Antiparallel
What type of double helix does our DNA form
-right handed
What type of bonding holds base bases together
-Hydrogen bonds
Explain which nitrogenous bases bind to which. What are their relative strengths?
What is the melting temperature (Tm) in regards to DNA
Temperature in which 50% of DNA becomes single stranded
Describe re-annealing
Event in which seperated DNA stranded (seperated base pairs) reforms hydrogen bond.
What is Chargaff’s Rule
- DNA from any cell of any organism should have a 1:1 stoichiometric ratio (base pair rule) of pyrimidine and purine bases
- means that amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.
What is mRNA
- linear single stranded molecule
- carries codon information for translation
- post transcriptionally modified -
- 2% of total RNA
what is tRNA
- folded stem loop structures formed by intramolecular H-bonding
- carries amino acid to ribosome
- 16% of total RNA
What is rRNA
- linear single stranded, folded molecule
- complexes with protein to form ribosome
- rRNA => important for forming polypeptide bonds
- 82% of total RNA
what is snRNA
- helps to mature pre-mRNA into mRNA.
- done via “splicing”
-Introns are removed (“introns in the trash”)
What are introns and exons
- Introns => Non-proteins coding regions
- Exons => Protein coding regions
- We want exons to remain in the mRNA during splicing
What are miRNAs
- miRNA regulate gene expression.
- Carry proteins complexes to the mRNA
- These proteins can inhibit translation in two different ways:
- 1) Block the ribosome form binding to mRNA
- 2) Degrade the mRNA
