topic 6 - Nucleic acids

Question 1

what is the primary structure of a nucleic acid?

Answer 1

primary structure:
- Nucleobases
- sugars
- phosphates
-nucleic acids

Question 2

what is the secondary structure of a nucleic acid?

Answer 2

Secondary structure:
- B-form
- A-form and Z-form
- Triplex and quadruplex DNA
- RNA structures

Question 3

what is the tertiary structure of a nucleic acid?

Answer 3

Tertiary structure:
- Nucleosomes
- DNA nanotechnology

Question 4

what are the components of Nucleic acids?

Answer 4

• base pair
• phosphodiester / phosphate
• deoxyribose

Question 5

what are the 2 Nucleobases structures to remember?

Answer 5

2 hydrogen bonds DA / AD
and
3 hydrogen bonds
ADD / DAA

Question 6

Primary structure and hybridisation

Answer 6

Primary structure = sequence of nucleotides.

duplex formed with strand of complementary sequence = complementary bases in opposite order.

Longer duplex with higher GC content = more stable

Question 7

what is hybridisation?

Answer 7

ATGTCTTGAACA What is the complementary sequence?

1/ Split strand into three-base units for clarity

ATG TCT TGA ACA

2/ Write down the complementary bases:

TAC AGA ACT TGT

3/ Reverse the order to give strand in 5’ to 3’ format:

TGT TCA AGA CAT

Question 8

why does duplex DNA (double helix) have a helical structure?

Answer 8

Negatively charged phosphate groups repel each other.

Base pairs hydrogen bond.

Stacking of nucleobases through hydrophobic / Van der Waals interactions compacts duplex vertically.

Question 9

what is the central dogma of biology

Answer 9

“The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred back from protein to either protein or nucleic acid.” – Francis Crick

Question 10

what does the ribosome do?

Answer 10

Huge complex of RNA and protein

Large ribosomal unit: links amino acids

Small ribosomal subunit: reads RNA

Question 11

what is RNA interference?

Answer 11

1) short interferring RNA [siRNA] designed to correspond to gene target
2) siRNA synthesised with drug-like properties: stability and conjugation for delivery.
3) Modified siRNA’s penetrate the cell membrane and harness the RNAi mechanism for gene silencing.
4) gene silencing achieves a therapeutic effect.