Organisation of the Human Genome Flashcards
The amount of DNA contained within a haploid nucleus or one half the amount in a diploid somatic cell of a eukaryotic organism is referred to as
the c value
what is the c value measured in
picograms or kilobases
what does the c value equate to in humans
3.2 x 10^9 bases or 6.55 picograms
what is the genome defined as
the complete dna sequence of an organism
what is the expectation of the c value
proportional to the genetic complexity (number of genes) of an organism
the number of genes in bacterial and archaeal genomes correlates with
the genome size and the complexity of the organism
does the number of genes in a eukaryote correlate with the genome size or the complexity of the organism
nope
what is the c value paradox
the lack of relationship between the dna content (c-value) of an organism and its coding potential
what percentage of the human genome consists of introns
24%
what percentage of the human genome consists of exons - protein coding sequences
1.2%
8.5% of the human genome is made of
protein binding sequences
on heating DNA what happens to it and what is this called
the strands separate and this is called DNA melting
melting involves what to happen to the DNA
progressive breaking of base pairs in the double helix
the melting temperature is determined by what?
the base composition of the DNA
which base pairs melt at a lower temperature
A:T base pairs melt at lower temperatures than G:C
the temp at which DNA is half unfolded is referred to as
the melting temperature Tm
the higher the G:C ratio the higher the
Tm
DNA melting can be followed in a
spectrophotometer
at what temperature is the chance in absorbance measured at in a dna melting curve
260nm
nucleotide bases absorb UV light at a wavelength of
260nm
if melted dna is rapidly cooled complementary strands remain
separated
if melted dna is slowly cooled then what will happen to the complementary strands
they will pair up again
what is the process of the strands pairing up again called
dna reannealing or renaturation
dna reannealing is the basis of which technique
dna hybridisation
what four factors is the rate of dna reannealing measured by
concentration, length, composition and complexity
the extent of dna reannealing is governed by
time
dna reannealing is measured by a
c0t value
what is a c0t value and what units
concentration x time in mols per second
the lower the c0t value the
less complex
dna reanealling experiments show that prokaryotic genomes are
kinetically simple
prokaryotic dna reanneals as if it were a
single unique length of dna with no sequence repeats
dna reannealing experiments show that eukaryotic genomes are
kinetically complex
eukaryotic genomes contain
several classes of dna
the fast component in c0t curve is
highly repeated dna sequences
the intermediate component of a c0t curve is
moderately repeated dna sequences
the slow component of a c0t curve is
non-repetitive or single copy dna sequneces
highly repetitive dna is present in almost all
higher eukaryotic genomes
what c0t range does highly repetitive dna have
low c0t range 10-4 to 10-2
highly repetitive dna doesnt have coding function, what does it do instead?
provide a structural function
repeats arranged head to tail in blocks of various lengths are called
tandem arrays
repeated regions interspersed within the chromosome are called
interspersed regions
what is the longest tandem array known
human alphoid dna
major classes of tandemly repeatedly human dna are classified according to size into which three classes
satellite, minisatellite and microsatellite
most random sequence dna has a similar buoyant density and forms part of the
main band
if one short sequence is repeated many times in a tandem array, it forms what in the equilibrium densitry centrifugation experiment
satellite DNA band
which two ways allow expansion of tandemly repeated human dna?
unequal crossing over and replication slippage
what does unequal crossing over result in
one recombinant with a deletion of material and one with a duplication
what does a replication slippage result in
each slippage adds one repeating unit to the daughter strand
where are microsatellites found
widely disperesed over the chromosome
where are minisatellites found
telomere
tandem repeats of which sequence minisatellite are found at the telomeres
TTAGGG
the centromere contains
various satellite components
structural intermediate repetitive DNA contains diff classes, these are
retrovirus/LTR retrotransposons, LINEs and SINES and then we have coding DNA
The LINE1 element has two open reading frames which are
ORF1 and ORF2
ORF1 encodes what
a rna binding protein
ORF2 encodes
a protein with both endonuclease and reverse transcriptase activities
Lines have a RNA mediated
transposition event
what does a retrovirus encode for
integrase and reverse transcriptase activities
retrovirus is a rna mediated
transposition event
give an example of a sines
alu repeat
infromational intermediate repetitive dna exists and contains genes for
histones, collagen, keratins, rRNA, tRNA
slow annealing dna is
unique
protein coding dna makes
mRNA
