Chapter 6 Flashcards
(22 cards)
What is the basic building block of DNA?
Nucleotide
A nucleotide consists of a 5 carbon sugar (deoxyribose), a phosphate group, and a nitrogen base.
What are the three parts of a nucleotide?
- 5 carbon sugar: deoxyribose
- Phosphate group
- Nitrogen base
The nitrogen base is attached to the #1 carbon by a glycosyl bond.
What type of bond connects the phosphate group to the 5 carbon sugar in a nucleotide?
Ester bond
How are the two strands of DNA joined together?
Hydrogen bonds between the base pairs
What is complementary base pairing in DNA?
- Adenine pairs with Thymine
- Guanine pairs with Cytosine
A purine always pairs with a pyrimidine, maintaining a constant diameter.
True or False: Adenine can pair with Cytosine.
False
What is the result of 32% adenine in DNA?
32% thymine, 18% guanine, 18% cytosine
This follows from the base pairing rules and the total percentage of bases in DNA.
What initiates DNA replication?
Origins of replication
What enzyme begins breaking the hydrogen bonds during DNA replication?
Helicase
What structure is formed when DNA strands unwind during replication?
Replication fork
What enzyme relieves tension in the DNA strands during replication?
Topoisomerases
What prevents the rejoining of separated DNA strands during replication?
Single-strand binding proteins (SSBs)
What direction does DNA polymerase III read the parent strand?
3’ to 5’ direction
What provides the energy needed for DNA strand synthesis?
Removing 2 phosphates from the nucleoside triphosphate
What is the role of RNA primase in DNA replication?
Builds a small complementary RNA segment (RNA primer)
What is the leading strand in DNA replication?
The template parent strand that begins at the 3’ end
The complementary strand is continuously made moving toward the replication fork.
What are Okazaki fragments?
Short segments of DNA synthesized on the lagging strand
What enzyme replaces RNA primers with DNA nucleotides?
DNA polymerase I
What enzyme catalyzes the connection of DNA segments, including Okazaki fragments?
DNA ligase
What is the proofreading function of DNA polymerase III?
Backtracks and replaces the wrong nucleotide if a mistake is found
What does DNA polymerase II do?
Repairs damage to DNA that occurs between replication events
Fill in the blank: DNA replication is discontinuous on the _______ strand.
Lagging
