B.8. Nucleic Acids Flashcards
The structure of Adenine and Guanine
Double ring structure consisting of a 6-sided ring attached to a 5-sided ring = PURINES
The structure of Cytosine, Thymine and Uracil
Single 6-sided ring = PYRIMIDINES
Which part of a DNA or RNA is charged?
Phosphate group
→ Partially responsible for water solubility of nucleic acids
Nucleotides polymerise to form what?
Nucleic acids (Polynucleotides)
What do Nucleic acids consist of?
+ chains of nucleotides formed by enzyme catalysed condensation reactions
Which C is the base covalently bonded to?
C1
Which carbon is the phosphate group attach to? And how does it attach?
C5 → phosphate group condenses w/ the -OH group of the sugar
How is the sugar-phosphate backbone formed in DNA and RNA?
The phosphate of one nucleotide combines w/ the hydroxyl group on the C3 of the sugar on another nucleotide = releasing water = forming covalent bond
How do the 2 strands of DNA bond together?
By H.bonding betw/ the complimentary base pairs located betw/ the 2 backbones of sugar and phosphate groups.
How many H.bonds do A and T form?
2 → form complimentary base pairings
How many H.bonds do C and G form?
3 → form complimentary base pairings
What is part of the reason for the AT and CG bases to only be able to pair together?
Only the molecular geometry of the single ringed and double ringed complimentary base pairs give a similar dist. betw/ the 2 backbones of DNA
What other forces stabilise the backbone of the double helix?
+ van der Waal’s force between base pairs
+ Dipole-Dipole forces between base pairs
Why is there twisting betw/ the sugar-phospate backbone of DNA?
To minimise the electrostatic repulsions betw/ negatively charged phosphate residues.
How many nucleotide completes a turn of a helix?
10
What allows DNA to replicate itself exactly?
The complementary base pairings
What is the role of DNA?
To reproduce itself and carry information which encodes the proteins in an organism.
What is a gene?
A section of DNA that codes for a protein.
What is the origin of the negative charge of the DNA?
The phosphate (ion) group
What is the strength of Phosphoric acid?
Weak = ionizes in water to reach acid-base equilibrium at that temp.
What do cells mostly contain?
Water
At the pH of cells what does the phosphate group in the nucleotide contain?
Negatively charged Oxygen atoms
What charge do histone proteins have?
Positive +
What makes it possible to remove or insert parts of DNA at diff places in or betw/ cells?
Restriction Enzymes (Restriction Endonucleases)
Benefits of GM foods (9)
1) Resistance to Herbicides = reduces use
2) Resistance to Pesticides = Don’t kill useful insects
3) Resistance to Diseases
4) Decreasing risk of food allergies = e.g. soybeans
5) Increase Yield
6) Resistance to harsh climates = Withstand cold/ salt
7) Nutrient enriched = Golden rice = for ppl lacking
8) Economics
9) Environmental = Less damage to water supply from herbicides and pesticides
Concerns of GM foods (6)
1) Impact on other organisms
2) Resistance to pesticides
3) Allergies
4) Gene-flow to other species = resistant weed
5) Labelling of GM foods = in some countries required but some not = should label to give consumer choice
6) Health effects
