Homologous recombination (HR) is a DNA metabolic process found in all forms of life that
provides high-fidelity, template-dependent repair or tolerance of complex DNA damages
including DNA gaps, DNA double-stranded breaks (DSBs), and DNA interstrand crosslinks (ICLs).
What type of damage does homologous recombination repair?
1.1 DNA Synthesis in Homologous Recombination
Homologous recombination (HR) faithfully repairs
complex DNA damage including DNA double-stranded breaks (DSBs)
by referencing an intact donor template in the form of the sister chromatid, a homolog, or an ectopic sequence.
Does homologous recombination repair DNA?
Homologous recombination is a major DNA repair process in bacteria
. It is also important for producing genetic diversity in bacterial populations, although the process differs substantially from meiotic recombination, which repairs DNA damages and brings about diversity in eukaryotic genomes.
What is the result of homologous recombination?
Homologous Recombination
Paired chromosomes from the male and female parent align so that similar DNA sequences from the paired chromosomes cross over each other. Crossing over results in
a shuffling of genetic material
and is an important cause of the genetic variation seen among offspring.
How does homologous recombination repair work?
Homologous recombination repair is a DNA repair process that includes
the invasion of an undamaged DNA molecule by a damaged molecule of identical or very similar sequence
. Resynthesis of the damaged region is accomplished using the undamaged molecule as a template.
What is the role of recombination in repairing damaged DNA?
Recombination repair is
a mechanism for generating a functional DNA molecule from two damaged molecules
. It is an essential repair process for dividing cells because a replication fork may arrive at a damaged site, such as a thymine dimer, before the excision repair system has eliminated damage.
How does homologous recombination repair double-strand breaks in DNA?
Repair of a DNA double-strand break by homologous recombination takes place
by means of replication, using the homologous strand as template
(see Figure 1). Homologous recombination therefore requires extensive regions of DNA homology in another DNA duplex, and no loss of genetic information normally results.
What mechanisms can repair DNA?
At least five major DNA repair pathways—
base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)
—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.
How does homology directed repair work?
Homology directed repair (HDR) is
a mechanism in cells to repair double-strand DNA lesions
. The most common form of HDR is homologous recombination. The HDR mechanism can only be used by the cell when there is a homologous piece of DNA present in the nucleus, mostly in G2 and S phase of the cell cycle.
How does homologous recombination affect independent assortment?
When genes are on the same chromosome but very far apart, they assort independently due to crossing over (homologous recombination). This is a process that happens at the very beginning of meiosis, in which
homologous chromosomes randomly exchange matching fragments
.
What is homologous DNA sequences?
Sequence homology is
the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life
.
What is the difference between homologous and nonhomologous recombination?
Two types of recombination are typically distinguished:
homologous recombination, where a fragment of a genome is replaced by the corresponding sequence from another genome
[4], and non-homologous recombination, which causes genetic additions of new material and is also called lateral gene transfer (LGT) [5].
How does recombination of DNA work?
Recombinant DNA technology is the joining together of DNA molecules from two different species.
The recombined DNA molecule is inserted into a host organism to produce new genetic combinations
that are of value to science, medicine, agriculture, and industry.
What is the difference between homologous recombination and crossing over?
The main difference between recombination and crossing over is that
recombination is the production of different combinations of alleles in the offspring whereas crossing over is the exchange of genetic material between non-sister chromatids
, the event which produces recombination.
What is the purpose of homologous recombination?
Homologous recombination (HR) is an important mechanism
for the repair of damaged chromosomes, for preventing the demise of damaged replication forks, and for several other aspects of chromosome maintenance
. As such, HR is indispensable for genome integrity, but it must be regulated to avoid deleterious events.
What is homologous recombination in gene therapy?
homologous recombination,
the exchange of genetic material between two strands of DNA that contain long stretches of similar base sequences
. Homologous recombination occurs naturally in eukaryotic organisms, bacteria, and certain viruses and is a powerful tool in genetic engineering.
What is homologous recombination Crispr?
Cas9-triggered homologous recombination is
a fast and inexpensive way to make essentially any desired change to the C. elegans genome
. The principle is simple: we use Cas9 to make a DNA double-strand break at a defined site in the genome.
Does homologous recombination occur in mitosis?
Mitotic homologous recombination occurs mainly between sister chromatids subsequent to replication (but prior to cell division)
.
How long does DSB repair take?
So for example, if you use alkylating agents like Temozolomide that cause replicative DSBs, you get DSBs with every replication cycle (24, 48, 96 hrs for most cells) and it usually takes
120 hours
for them to disappear completely.
Which of the following occurs in the repair of double strand DNA breaks by recombination quizlet?
Which of the following is true of repairing double-strand breaks by recombination?
The 3′ single strand extensions invade the homologous chromosome,displacing the homologous strand and base pairing with the complementary strand
.
How long does it take for DNA to repair?
They found that the DNA of transcribed genes was just about fully mended in two circadian cycles, Sancar said. Restoration of these genes composed the majority of repair during the first
48 hours
but afterward, repair of nontranscribed DNA became dominant and proceeded for weeks.
Which type of repair is a backup for the DNA polymerase proofreading function?
In mismatch repair, the sugar phosphate backbone is fixed, whereas in nucleotide excision repair, several nucleotides are replaced. Which type of repair is a backup for the DNA polymerase proofreading function?
uses an undamaged segment of DNA as the template to repair a damaged segment of DNA
.
Is DNA polymerase a repair mechanism?
DNA polymerase alpha is required for semi-conservative replication of DNA but
not for repair of DNA
. A more recently discovered enzyme, DNA polymerase zeta, appears to be involved in the bypass of damage, without excision, and occurs during DNA replication of a damaged template.
