DNA Replication
heterochromatin vs. euchromatin
-during replication, DNA must be uncondensed -heterochromatin is what remains compacted and is transcriptionally silent with highly repetitive sequences -euchromatin is dispersed, therefore genetically active DNA that gets copied during replication
If a DNA molecule is found to be composed of 40% thymine, what percentage of guanine would be expected?
10%
When one DNA molecule is copied to make two DNA molecules, the new DNA contains
100% of the parent DNA
DNA replication results in
2 DNA molecules that each contain a strand of the original
DNA replication results in:
2 DNA molecules that each contain a strand of the original
If the DNA of a certain organism has guanine as 30% of its bases, then what percentage of its bases are adenine?
20%
If 32% of the bases in a DNA molecule are adenine, which of the following describes the adbundances of the other bases?
32% thymine, 18% cytosine, 18% guanine.
Nucleoid
In the cytoplasm
DNA polymerase can make mistakes while adding nucleotides. How does this gets fixed?
It edits the DNA by proofreading every newly added base as the polymerization continues.
Nucleo excision repair is important particularly in __________.
thymine dimers: caused by ultraviolet light.
Supercoiling
twisting in the opposite direction to the turns of the double helix during the first stage of mitosis.
DNA replication
uses each strand of a DNA molecule as a template for the creation of a new strand
DNA polymerase
An enzyme that catalyzes the formation of the DNA molecule.
If one strand of DNA is CGGTAC, the corresponding strand would be
GCCATG
In the ladder analogy of the DNA molecule, the "rungs" of the ladder are:
sugars, phosphate, pair nitrogenous bases
The replication of DNA occurs during the __________________ of the cell cycle, before the cell enters mitosis or meiosis.
synthesis phase, or S phase before mitosis and meoisis.
Primase
synthesizes RNA primer
The copying mechanism of DNA is most like
taking a picture of yourself and of your reflection in a mirror.
During DNA replication, each strand serves as a ____________ for the new ____________ strand.
template, complementary
Prymidines
thymine and cytosine
The process of proofreading involves
removing incorrect bases during replication
Which of the following occurs in the nucleus?
replication of genetic material
Which of the following statements about these strands is true?
the leading strand of DNA is synthesized continously
Chargaff showed that
the numbers of Adenine and Thymine are the same in DNA from an organism.
One dangerous mutation that can occur due to the sunlight exposure (ultaviolet light) is called
thmine dimer
The "rule" forumlated by Chargaff states that
A = T and G =C
An example of base complementation in DNA replication is
A and T
phosphate group
A chemical group consisting of a phosphorus atom bonded to four oxygen atoms; important in energy transfer.
lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' to 3' direction away from the replication fork.
Deoxyribose
A five-carbon sugar that is a component of DNA nucleotides
DNA ligase
A linking enzyme essential for DNA replication; catalyzes the covalent bonding of the 3' end of a new DNA fragment to the 5' end of a growing chain.
Purines
Adenine (A) and Guanine (G)
Telomerase
An enzyme that catalyzes the lengthening of telomeres. The enzyme includes a molecule of RNA that serves as a template for new telomere segments.
nitrogenous base
An organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA
nucleotide excision repair
Another type of repair when the DNA double strands are unzipped and separated - the incorrect bases are removed along with a few bases on the 5' and 3' end, and replace by copying the template with DNA polymerase.
Telomeres
DNA at the tips of chromosomes
Nucleosomes
DNA coiled around histones (proteins that help organize and pack DNA)
Which statement regarding DNA is false? - DNA contains the sugar deoxyribose. x - DNA contains the nitrogenous base uracil. - One DNA molecule can include four different nucleotides in its structure. - DNA molecules have a sugar-phosphate backbone.
DNA contains the nitrogenouse base uracil.
One difference between the structure of DNA in eukaryotes and prokaryotes is
DNA in eukaryotes is linear and DNA in prokaryotes is circular.
The enzume that joins together the sugar-phosphate backbones of DNA segments is called
DNA ligase
Which enzyme catalyzes the elongation of a DNA strand in the 5' to 3' direction?
DNA polymerase
Which of the following enzymes catalyzes the elongation of a new DNA strand?
DNA polymerase
How good is the DNA repair process?
DNA polymerase makes an error once 50K-100K pairs
When a cell divides, it is important that each daughter cell receives an identical copy of the DNA by the process of
DNA replication.
Which of the following statements best explains the mechanism for DNA replication?
DNa replication is semi-conservative, because each DNA strand serves asa template during replication.
What happens during DNA replication?
Each of 2 strands of double helix serves as a template from where new strands are copied.
Which of the following correctly pairs the DNA replication enzyme with its function? - Helicase seals the gaps between DNA fragments - DNA polymerase I open up the DNA at the replication fork - DNA primase extends primers by adding the nucleotides to the 3' end x - Ligase works to seal the gaps between DNA fragments
Ligase works to seal the gaps between DNA fragments.
anti-parallel
Separate strands that run in a different direction. In a DNA molecule, one strand is in the 3' to 5' orientation, and the other is in the 5' to 3'orientation.
Complementation
The DNA polymerase moves to the next nucleotide on the original strand and randomly places nucleotides across from it. If it's not the right nucleotide, it will fall back out. Finally, locks in the right base by the phosphate of this new nucleotide to the sugar of growing new DNA strand.
Which statement regarding a DNA double helix is true?
The amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to the amount of cytosine.
How does the DNA fit into the nucleus of the cell?
The circle of the DNA is crowded and held together in the center by scaffolding proteins. Then the DNA is twisted beyond the double helix (supercoiling). Finally, the DNA condenses to 1/1000th of its original size.
Primer
The initial nucleotide chain that is produced during DNA synthesis is actually a short stretch of RNA
leading strand
The new continuous complementary DNA strand synthesized along the template strand in the mandatory 5' to 3' direction.
What is the role of the phosphate group in DNA?
The phosphate group bonds covalently with the sugar molecule of the next nucleotide, and so on, forming a long polymer of nucleotide monomers.
Helicases
Unzips DNA and separate the template DNA strands at the replication fork.
The Nobel Prize in 1963 was awarded to
Watson, Crick, and Wilkins
Which statement about the discovery of DNA structure by Watson and Crick is false?
X-Ray pictures of DNA were helpful in deducing its structure.
Chargaff's Rule
[A]=[T] and [G]=[C], they pair up across from one another forming two strands also called base pairing.
Mutation
a permanent change in the DNA sequence.
DNA
a polymer of nucleotides consisting of a nitrogenous base, deoxyribose, and a phosphate group.
DNA polymerases require
a primer and a DNA template strand
The shape of a DNA molecule is most like
a twisted rope ladder
The 4 types of nitrogenous bases in DNA are:
adenine (A), thymine (T), guanine (G), or cytosine (C).
mismatch repair
are enzymes in which recognize the wrong incorporated base and excise it from the DNA by replacing the correct base.
Why does a DNA strand grow only in the 5' to 3' direction?
because DNA polymerases can only add nucleotides to the 3' end of the growing molecule.
single strand binding proteins
bind to and stabilize single-stranded DNA
Wilkins and Franklin
both used a technique called x-ray crystallography to produce a picture of the DNA molecule
Mutation may lead to
cancer
Heterochromatin
condensed chromatin
In DNA, guanine from one strand binds to _____________ in the complementary strand.
cytosine
Considering the principle of complementary base pairing, you would expect an equal ratio of which two nitrogenous bases in a DNA molecule?
cytosine and guanine
Histones
the proteins that the DNA uses to wrap around to form nucleosomes.
James Watson and Francis Crick
discovered the structure of DNA
Why is replication called semi-conservative?
each daughter cell gets part of the original DNA & part of the new DNA.
Semiconservative DNA replication means that
each new DNA molecule has half the DNA from the old one
Telomeres tend to
get shorter during each cell division
DNA can be retieved from
hair, blood, or saliva.
The enzymes that break hydrogen bonds and unwind DNA are:
helicases
Condensed chromatin is called
heterochromatin
Base pairing is dependent on
hydrogen bonds
Euchromatin
loosely packed chromatin
If errors are not corrected in DNA, they may result in
mutation.
semiconservation replication
new DNA consists of one old strand and one new strand
Histones are proteins that make up
nucleosomes
Semiconservative replication refers to
one old strand of DNA is used to provide the information for the new strand of DNA.
During replication, which enzyme adds complimentary base?
polymerase