DNA Structure And Repliction Flashcards
What is heterochromatin
Darker stained
Tightly packed DNA
What is euchromatin
Loosely packed DNA
Lightly packed
What is a nucleosome
8 Histone subunits core with 2 bits of DNA wrapped around it
What is a histone
8 sections of histone subunits- histone octamer
What are beads on a string
Euchromatin- loosely packed
What is a solenoid
Heterochromatin
- tightly packed beads on a string
What is the difference between a nucleoside and a nucleotide
No phosphate
What are purines
2 ringed
Guanine adenine
Pyramidine
1 ring
Cytosine
Thymine
Uracil
What does it mean that the primary structure of DNA has polarity
5’ to 3’
Has distinct ends 5’P and 3’OH
Which bases pair
Guanine and cytosine 3 hydrogen bonds
Adenine and uracil/ thymine 2 hydrogen bonds
Secondary structure of DNA
DNA strands complimentary and anti-parallel
Each single strand held together by covalent bonds between sugars-phosphates
Double strand held together by hydrogen bonds formed by the complementary base pairs
What is semi-conservative replication fo dna
Each old strand acts as a template for a new DNA strand
What way does dna replication go
From 5’ to 3’
Initiation of DNA replication
Recognition of origin of replication
• Requires recruitment of DNA polymerase (+ other proteins)
• Requires a ‘kick-start’ by DNA primase (making a short
RNA primer) as DNA polymerase can only extend a 3’end
• One origin of replication results in two replication forks
