Lecture 1: Nucleic acid structure and replication Flashcards
What are the 4 heterocyclic bases that make up the DNA sequence?
Adenine, Thymine, Guanine, Cytosine
What is a purine and what are the 2 heterocyclic bases examples?
A purine consists of 2 rings;a double ringed crystalline base: Adenine, Guanine
What is a pyrimidine and what are the 2 heterocyclic base examples?
A pyrimidine consists of one ring, crystalline base:
Cytosine, Thymine
How many hydrogen bonds form between C-G and what is consequence of this?
3 Hydrogen bonds form between C-G in comparison to A-T which bonds to each other with 2 hydrogen bonds. In consequence C-G requires more energy to separate.
what is the DNA backbone made of
2’- deoxyribose
What orientation does the DNA double helix conform to?
Right handed helix
What are the major components of RNA and how are DNA and RNA different?
RNA is one stranded
thyamine is replaced by uracil
ribose sugar instead of deoxyribose
true or false, DNA bases are hydrophobic
true
What is the consequence of the hydrophobic property of DNA bases?
They will tend to form a structure which removes them from an aqueous environment (double helix)
true or false, DNA soluble in water
true, this is because the DNA backbone is hydrophilic because it exposes its sugars
What do you call the process in which DNA is wound?
Supercoiling
What is a twist (T)
A twist is the number of turns (always + ve)
What is a writhe (W)
It is the number of times strip crosses over itself (always -)
What is the link number (L)
W+T
what enzyme breaks the ddsDNA and pass another part of the strands through the gap?
Type II Topomerases
which region on the DNA strand binds more strongly?
regions with high G-C content
