DNA Replication Flashcards
Lecture 1
Describe histone interaction with DNA (Linkers, nucleosomes etc.)
DNA wrapped around histones (proteins), this complex is called a Nucleosome
Unwrapped parts are called Linker DNA
What is a solenoid? What is its width?
DNA coiled further into a 30nm wide complex.
What is Euchromatin?
Stringed DNA, loosely packed (Histone-DNA complex)
What is Heterochromatin?
Tightly packed DNA (solenoids)
Are genes expressed in Heterochromatin or Euchromatin?
Euchromatin
What is a gene?
Genes are DNA sequences which code for protein production
What is a nucleoside?
A nitrogenous base attached to a sugar, but NO PHOSPHATE.
What sugar is present in nucleotides?
Ribose (pentose)
What is the difference between DNA and RNA?
Sugar phosphate backbone on DNA lacks oxygen on 2nd carbon molecule (2-deoxyribose)
How is phosphate bonded to the pentose sugar? What is the bond called?
Binded to the 5th carbon on the pentose sugar. Called a Phosphodiester Bond.
What is the difference between Purine and Pyrimidine?
Purine has 2 rings to its bases. Pyrimidines have one ring.
Which bases are Purine?
Adenine and Guanine
Which bases are pyrimidines?
Cytosine, Uracil and Thymine
What is the nomenclature for a ribonucleotide?
Adenosine Monophosphate (AMP)
What is the nomenclature for a deoxyribonucleotide?
Deoxyadenosine Monophosphate (dAMP)
How do hydrogen bonds form between DNA base pairs?
H-bonds form between electronegative Oxygen molecules and electropositive Hydrogens on N-H bonds.
What are Major and Minor Grooves?
Major is a larger gap between phosphate groups, minor is the opposite.
Explain how (step wise reaction) a nucleotide strand increases in size.
dNMP + dNTP —-> (dNMP)+1 + PPi
Hydrolysis of Triphosphate (Pyrophosphate Hydrolysis) generates energy for reaction to occur.
Catalysed by DNA Polymerase
DNA Replication - Describe and Explain Initiation.
DNA Helicase breaks H-bonds and unzips DNA creating replication forks
RNA Primase binds to specific DNA sequence
DNA Polymerase binds to Primase (needs double strand)
DNA Replication - Describe and Explain Elongation.
Elongates from 3’ end to 5’ end
Opposite way of each strand so create a leading strand and lagging strands (Okazaki Fragments)
DNA Ligase joins fragments
DNA Replication - Describe and Explain Termination.
Two replication forks meet and DNA Ligase joins final fragments.
Results in 2 old strands and 2 new strands.
