DNA structure, replication

Question 1

What is needed for DNA synthesis/replication?

Answer 1

DNA template
Deoxynucleoside tri-phosphate
Protein complex (DNA polymerase)
DNA or RNA ‘primer’
Divalent metal cations (Mg2+)

Question 2

What is the central dogma?

Answer 2

Information flows unidirectionally from DNA to RNA to protein

Question 3

What is the exception to the central dogma?

Answer 3

Retrovirus: converts RNA genome back to DNA

Question 4

Explain the mechanisms of replication

Answer 4

DNA replication catalyzed by DNA polymerase
Addition of nucleotides
dNTPS are hydrolyzed

Question 5

What is the difference between DNA and RNA polymerase?

Answer 5

RNA pol. -> does not need primer
DNA pol. -> does need primer

Question 6

What are the proteins that assist in DNA replication?

Answer 6

DNA helicase: unwinds double helix
Single-strand binding proteins: stabilize template strands
RNA primase: catalyzes synthesis of short RNA primase to which nucleotides added
DNA polymerase III: extends strands 5’-3’

Question 7

Explain RNA primase

Answer 7

Enzyme uses single stranded DNA as template to synthesize short complementary RNA primer

Question 8

DNA replication on leading strand

Answer 8

DNA is copied continuously 5’-3’ direction
After an RNA primer is made, DNA pol III starts to synthesize leading strand

Question 9

DNA replication on lagging strand

Answer 9

DNA copied in Okazaki fragments
DNA pol III only synthesizes DNA until RNA-primed start of next fragment
DNA pol I takes over and replaces RNA with DNA
Phosphodiester bond completed by DNA ligase

Question 10

What does RNA primase do?

Answer 10

Provides primer for DNA pol III to extend strand