DT - DNA Structure Flashcards
What bases are Pyramidines and how many rings do they have?
- Cysteine
- Thymine
1 ring
What bases are Purines and how many rings do they have?
- Guanine
- Adenine
2 rings
What do a Sugar and Base form?
Nucleoside
What do Nucleoside and Phosphate form?
Nucleotide
What is Chargaff’s rule?
The 4 nucleotides are not present in the same amounts, however:
A = T
G = C
Purines = Pyramidines
What is the distance between nucleotides discovered by Rosalind Franklin and Maurice Wilkins?
0.34nm
What did Watson and Crick discover?
- A forms 2 hydrogen bonds with T
- G forms 3 hydrogen bonds with C
What are some properties of DNA?
- Bases are HYDROPHOBIC
- Van der Waal interactions between stacked bases
- Phosphates present on the outside so the molecule is NEGATIVELY charged
- The 2 strands are ANTIPARALLEL
(5’ –> 3’)
What are some properties of B-DNA?
Right-handed structure
Forms deep major and minor grooves
What are some properties of A-DNA?
Right handed
Formed when DNA is dehydrated
What are some properties of Z-DNA?
Left-handed
Formed by some GC-containing sequences at high salt concentrations
What has higher absorbances, single-stranded or double-stranded DNA
SIngle-stranded DNA (Bases are no longer stacked on both sides)
Why do GC-rich DNAs melt at a higher temperature than AT-rich DNA?
Contain 3 hydrogen bonds as opposed to 2
What happens to the melting point when salt concentrations are increased?
Melting point increases as positive ions neutralise repulsive negative phosphate groups on the backbone (More stable)
How is DNA condensed in eukaryotic cells?
In the form of Chromatin
