V L5: Organisation of the human genome Flashcards
is Genome size and gene content the same in every species?
no it varies a lot
How big is a Haploid human genome ?
3.1 x 10^9 nucleotides
Name three parts of a chromosome and their loccation ?
centromere - middle
telomere - bottom
chromatid - bottom length
what is a centromere?
Constricted region, required for segregation of daughter chromosomes.
what is a telomere?
Region located at the ends of chromosomes, that protect the end of the chromosome.
where does the o allele have a DNA base detection?
in exon 6
what does the DNA base detection in the O allele cause?
a reading frame shift, leading to a truncated protein lacking the catalytic domain. (Frame shift mutation)
A allele produces _________ leading to addition of __________ to the existing O/H _____.
A- transferase
N-acetylgalactosamine
antigen
B allele produces _______ , leading to addition of ____ to the existing O/H antigen.
B-transferase
galactose
what does RNA splicing do?
RNA splicing remove unwanted introns from the mRNA transcript.
what happens after introns are removed from the mRNA transcript ?
The remaining exonic segments are joined to produce a shorter RNA product.
what happens once a shorter RNA product has been produced?
A specialised nucleotide guanine is added. This is known as 5ʹ capping.
After transcription 3ʹ cleavage reaction what happens?
enzyme adds adenylate (polyadenylation), produces a poly (A) tail.
which part of the final mRNA molecule is translated?
Only a central segment
One pre-mRNA =
different proteins
what percentage of a gene is repeated sequence?
46%
what can be found as part of the unique sequence?
Genes (Exons) < 2% Introns/UTRs Pseudogenes Gene fragments/truncated genes Unique low copy non-repetitive DNA
Genes can…
appear in clusters
share common sequence motifs
are present in multiple copies
what is a Pseudogenes?
Pseudogenes appear to have arisen by insertion of processed mRNA and are no longer functional
What are the 2 types of Pseudogenes?
Conventional (gene relic)
Processed
what causes conventional Pseudogenes?
caused by a single point mutation causing a non-functional gene that over time will degrade.
what are processed Pseudogenes?
believed to be processed mRNAs that have been converted to DNA by reverse transcription and re-incorporated into the genome
are processed Pseudogenes usually found in clusters?
yes
what causes a gene fragment?
Genes can become damaged over time leaving remnants of the original gene behind
what are the 2 types of repeated sequences?
Genome wide interspersed DNA (transposons)
- Tandemly repeated DNA (simple sequence repeats)
Genome wide interspersed DNA is present as what?
multiple copies interspersed throughout the genome
How does Genome wide interspersed DNA propogate?
via an RNA intermediate (retro-elements) or by DNA transposition
Genome wide interspersed DNA may be autonomous or non- autonomous. true or false?
true
Genome wide interspersed DNA is mobile? true or false?
True, move from one site to another
whats a LINE?
Long Interspersed Nuclear Element
whats a SINE?
Short Interspersed Nuclear Element
whats satellite DNA?
tandem arrays of 5-200 bp repeat units, 100s kb in length, associated with centromeres, 90% AT
what is Mini-satellite DNA ?
tandem arrays up to 20kb with repeat units of up to 6-100bp associated with telomeres
what is Micro-satellite DNA ?
tandem array of 1-6 bp repeat unit, up to 150bp
very common in genome, prone to mutation so very useful for genetic profiling
what are some classes of satellites?
Several classes of satellite DNA: Alphoid (α)satellite DNA Beta (β) satellite DNA Satellite 1 Satellite 2 Satellite 3
Mini-satellites with similar sequences are found. where?
multiple locations within the genome
why are mini satellites useful?
hybridising a mini-satellite probe to restriction digested DNA on a Southern blot will pick up multiple bands
- every person has a different pattern of bands
when were micro satellites introduced into forensic casework?
mid 90s
what are microsatellites also known as?
STRs
Microsatellites are used how?
Typically use tetranucleotide repeats (4 bp).
Micro and mini-satellites are prone to expansion and contraction at _____.
meiosis
what used to be used to look at the differences in DNA sequence ?
ultracentrifugation
Re-association kinetics
what current methods are used to classify specific DNA sequences?
Amplification of specific DNA
Detection of specific DNA using hybridisation
what happens in a buoyant density study?
- genomic DNA has a GC content of about 40% and forms the main band
- repetitive sequence have very different GC contents and form satellite bands
