Class notes
Genomes and recombination
- Course
- Institution
- Book
A summary of the lectures covering the human genome, genetic variation and homologous and non-homologous recombination.
[Show more]
Connected book
Book Title:
Author(s):
- Edition:
- ISBN:
- Edition:
More summaries for
-
Summary Course 9 Plant Biology term 2
-
RNA, transcription and processing
-
Gene expression and post-transcriptional modification
Seller
Follow
Alysmay
Reviews received
Content preview
Mitosis Homologous recombination in prophase I of meiosisSomatic cells Homologous chromosomes pair and crossing over occurs at chiasmata. It
2n -> 2n + 2n (1n -> 1n + 1n for involves the breaking and joining of DNA. It is reciprocal and results in genetic
haploid organisms)
rearrangement.
Genetically identical daughter
1) Double strand break by Spo11 and Mre11 (nuclease complex)
cells
Homologous chromosomes 2) Exonuclease degrades 5’ ends around break site to generate 3’ overhangs
remain separate throughout. (so genetic material is initially lost – but it is reformed)
3) An overhand invades the sister chromatid/ homologous chromosome,
Meiosis forming a branch point.
Haploid gamete production 4) Heteroduplex structure – genetic information from one origin, binding with
2n -> n x4
another. This structure formed is called a D-loop
Genetically different daughter
5) DNA is synthesised from the branch point
cells
Homologous chromosomes pair 6) Continued synthesis and ligation forms a double Holliday Junction
and recombine. 7) To resolve these Holliday Junctions, DNA is broken and re-joined. If the
strands are both cut on the same (horizontal) plane, there is no crossing
over. If the strands are cut of different planes (one horizontal one vertical,
there is crossing over)
Recombination can be used for:
1) Linkage analysis by measuring the recombination frequency of genes. Large
distance = high recombination frequency. Use transcription genetics by
looking at the frequency of recombination between generations
2) Gene targeting. Use a homologous sequence with a suitable marker. Circular
DNA: single crossover, insertion of sequence into the gene (gene disrupted).
Linear DNA: 2 regions of homology, double crossing over, deletion of gene.
Homologous recombination can occur in bacteria with circular (plasmid) DNA (all
inserted) or a piece of linear DNA (removal of homologous original).
Recombin Bacteriophages can make use of
this to make recombinants.
Homologous recombination – repair of dsDNA
8) Double strand break by Spo11 and Mre11
(nuclease complex)
ation Heteroduplex formation
Synapsis (fusion) of the chromosomes (3) is catalysed by
9) Exonuclease degrades 5’ ends around break site to Rad51 (or RecA in bacteria) and other proteins. The
generate 3’ overhangs (so genetic material is enzyme bins to the 3’ single strand end of damaged DNA
initially lost – but it is reformed) forming a dynamic 3-stranded structure. The enzyme
10) An overhand invades the sister chromatid/ then searches for homology.
homologous chromosome, forming a branch It is called heteroduplex formation as the single,
point. complementary strands which have combined were
11) Heteroduplex structure – genetic information derived from different sources.
from one origin, binding with another. This
structure formed is called a D-loop
12) DNA is synthesised from the branch point
13) The newly synthesised DNA is paired with the top
strand for its DNA synthesis
14) The repairs are then joined into the DNA by DNA
ligation
This is a very accurate repair process compared to
non-homologous recombination – a process only used
why homologous recombination isn’t available.
Repairs accurately, is universal, non-reciprocal (one
way exchange), but it can cause a loss of
heterozygosity.
Non-homologous recombination
The ends of the strands close to the double strand
break are degraded, causing the loss of genetic
material. The ends are then joined through ligation.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Alysmay. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.86. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
53022 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now