Genetics Exam 3: Replication & Recombination

How many base pairs exist in the human genome?

3 billion

What did Watson and Crick discover in terms of the DNA arrangement?

each strand of a DNA double helix could serve as a template for the synthesis of its component

What is semiconservative replication?

Each replicated DNA molecule consists of one “old” and one “new” strand

What is conservative replication?

Two newly synthesized strands come together—original helix is conserved

What is dispersive replication?

Parental strands are dispersed into two new double helices

-parent strand is cleaved

Where does DNA replication begin?

origin of replication (ORI)

What structure begins to form at the replication site when the helix unwounds?

replication fork

T/F: replication is unidirectional

False, it is bidirectional

What is a replicon?

unit of length of DNA replicated

How many points of origins do prokaryotes and eukaryotes have?

prokaryotes = one

eukaryotes = multiple

How does chain elongation occur?

in the 5’ to 3’ direction by adding one nucleotide at a time to 3’ end

What is the role of an exonuclease?

to remove nucleotides

What does DNA polymerase I, II, and III do?

elongates existing DNA strand with a primer

-cannot initiate DNA synthesis

What is the purpose of exonuclease activity in 3’-5’ for DNA polymerases

proofreads and corrects synthesized DNA

What only occurs in DNA polymerase I

contains exonuclease activity in the 5’-3’ direction that excises primers and fills in gaps

What is the role of DNA polymerases I, II, IV, and V

involved in DNA repair, such as damage from UV light

What is DNA polymerase III holoenzyme

Active form of DNA Pol III

What are the core subunits a holoenzyme contains

▪a – 5’–3’ polymerization

▪e – 3’–5’ exonuclease

▪q – Core assembly

What are the 7 issues that must be solved during DNA replication

Unwinding of helix

Reduce coiling

Synthesizing primers

Discontinuous synthesis of second strand

Removal of RNA primers

Joining of gap-filled DNA

proofreading

What is DnaA

initiator protein that binds to ORI causing conformation change

-makes helix open up & exposes ssDNA

What is the purpose of DNA helicase

recruits holoenzyme to bind to replication fork and initiate replication (“unzips” DNA)

What is an SSBP

single stranded binding proteins

-stabilizes the opened helix

What is DNA gyrase

relieves coil tension

T/F: DNA polymerase III can synthesize both directions

False, only 5’-3’

What does continuous synthesis contain

the leading strand

What does discontinuous synthesis contain

the lagging strand

What are lagging strands synthesized as

Okazaki fragments

What is an integral part of replication?

error correction & proofreading

Which enzymes and proteins are essential for DNA synthesis?

DNA polymerase III core enzymes

SSBPs: single-stranded binding proteins

DNA gyrase

DNA helicase

RNA primers

Does DNA replication in eukaryotes take less time than prokaryotes?

Yes, because eukaryotes contain more ORI

What makes eukaryotic DNA replication more complex?

contains more DNA than prokaryotes and has linear chromosomes

What is the pre-RC (prereplication complex)

will assemble at ORI and helps ORI become tagged

What does RNA polymerase create in prokaryotes

RNA primers

What is chromatin

Eukaryotic DNA complexed with binding proteins