Lecture 11 - DNA structure Flashcards
What was Chargaff’s discovery?
There is significant DNA variation between species, thus DNA could be the genetic material.
What are Chargaff’s rules?
- [A] = [T] and [G] = [C]
- The composition of DNA varies between species
What is the structure of DNA?
A double stranded helical molecule with particular features
What did the X-ray Diffraction Pattern of DNA show?
DNA:
- Helical structure
- Bases perpendicular to the length of the DNA molecule
- Double stranded
Nucleotide monomers are joined together with phosphodiester
bonds to form…
A polynucleotide =nucleic acid
(deoxyribonucleic acid for DNA)
How are DNA and RNA strands synthesised?
In a 5 –> 3 direction
T or F
The two strands of DNA are parallel
False
They are anti parallel
How many hydrogen bonds do C-G pairs have?
3 Hydrogen bonds
How many hydrogen bonds do A-T pairs have?
2 Hydrogen bonds
What does the Watson-Crick model of DNA structure show? (5)
- DNA has a double stranded helical structure
- The sugar phosphate backbone is on the outside
- The bases are on the inside
- Stabilised by hydrogen bonds
- The two polynucleotide strands are oriented in opposite directions
What did the Watson-Crick model provide? (2)
- a stimulus for deciphering the
genetic code - a possible mechanism for the
replication of DNA
What is a semi-conservative model of replication?
Each DNA strand of the double helix is used as a template strand for the synthesis of two new strands.
What are the two types of bases?
Purine (G and C) and Pyrimidines (T and A)
Which nucleotide component(s) are located on the inside of the DNA helix?
Bases (ATGC)
Which nucleotide component(s) are located on the outside of the DNA helix?
Sugar phosphate backbone
