Chapter 14 Flashcards
DNA Structures and Functions (35 cards)
monomers that make up DNA
Nucleotide
the 3’ end of one strand faces the 5’ end of the other strand
anti-parallel
specific nucleotide sequences where DNA begins to unwind
origin of replication
Y-shaped structure formed during initiation of replication
replication fork
strand that is synthesized continuously in the 5’-3’ direction, which is synthesized in the direction of the replication fork
leading strand
during replication, the strand that is replicated in short fragments and away from the replication fork
lagging strand
DNA fragment that is synthesized in short stretches on the lagging strand
okazaki fragments
DNA at the end of linear chromosomes
telomere
Approximately how many base pairs make up a haploid human genome? How many functional genes does it contain?
3 billion base pairs and 20,000-25,000 functional genes are contained in them
What are the building blocks of nucleic acids?
nucleotides
What are the three main components of nucleotides? How do the four nucleotides differ? How does DNA differ from RNA?
nitrogenous base, pentose sugar (5-Carbon), and phosphate group
They differ based on the nitrogenous base (AGCT)
Sugar
Describe the phosphodiester linkages in nucleic acids. What is the significance of the 5’ to 3’ phosphodiester bond?
nucleotides are joined by phosphodiester bonds which are covalent bonds
phospate connects to the hydroxyl of 5’ and one nucleotide of the 3’
How are the nitrogenous bases paired in the double helix? What type of bond holds them together? How many bonds in each pairing?
T double bonds with A and C double bonds with G through Hydrogen bonds
What does it mean to say the two strands of DNA in the double helix are “complementary?” What does it mean to say they are “anti-parallel?”
The nucleotides pair together and the strands are “opposite:
the strands are flipped 5’ matches with 3’
How do the complementary and anti-parallel characteristics of DNA influence how it replicates?
easy to replicate and make a second strand and determines how it is replicated
In DNA replication, the two “old” strands of DNA serve as templates for two new strands. How are the old and new strands paired after replication?
semi conservatively
one old strand pairs with a new one
In Eukaryotes, the chromatin has two different regions. What are they called? How are the similar? How are they different?
Heterochromatin is tightly packaged and the genes are not typically expressed
Euchromatin is less dense and the genes are usually transcribe or read
What is the main enzyme involved in DNA replication?
DNA polymerase adds nucleotides to the growing chain complementary to the template strand
Prokaryotes have how many types of DNA Pol? What are the main function of each
3
III is DNA synthesis
II is DNA repair
I is both
What is the significance of the origin of replication? How does this site(s) differ from prokaryotes to eukaryotes?
where DNA begins to unwind and lets the replication machinery know where to begin
Prokaryotes only have one and eukaryotes have multiple
What is the function of the helicase enzyme? How does it accomplish this task?
opens/unzips the DNA and forms the replication fork
unzips by breaking hydrogen bonds within the nitrogenous base pairs
Where are the replication forks and what takes place in these regions?
Where DNA has opened and single-strand binding proteins coat the single strand to prevent it from reattaching
How does the cell prevent the DNA from winding back up following the helicase?
single-strand binding proteins coat the single strands of DNA
What is topoisomerase enzyme? Why is it important? How does it accomplish its task?
moves along the DNA molecule ahead of the helix to prevent overwinding of the double helix
causes temporary nicks in the DNA structure and then reseals it
