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17 Cards in this Set
- Front
- Back
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what must DNA markers be? |
1) Polymorphic, tow or more alleles present in population
2) easy to assay/ distinguish between each allele |
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Short tandem repeats (STP's) |
also called microsatellite repeats
they are short tandem repeats , usually non-coding and 2-4 nucleotides long
longer ones ( >10) are called minisatellite repeats |
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how is forensic analysis using SRT's carried out? |
polymerase chain reaction amplifies 12 STR's, these are then seperated using electrophoresis to give a DNA prophile.
every individual will have a unique one
allows for even small samples to be used as they are amplified |
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single nucleotide polymorphisms (SNP's) |
these are single base pair differences, mostly non-coding
in humans 1-1000 base differences
most common type of polymorphism in genome |
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what is the theory behind genetic mapping of human disease genes? |
the idea is to identify a marker that shows linkage with the disease phenotype
solution:
used large number of markers spaced 20cM apart, need about 250-500 |
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what is a haloype? |
A halotype is a particualar combination of SNP's in small region of chromosome
many halotypes are shared in populations, but vary in frequency, or are unique to some populations |
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Once linkage betweeen a marker and disease phenotype has been found, what happens? |
Use positional cloning, repeat the linkage analysis using closely spaced DNA markers
then candidate genes are inspected and compared to human genome sequence |
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What organelles contain extranuclear DNA |
mitochondria and chloroplasts |
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how is the DNA in the extranuclear genomes thought to have arisen? |
endosymbiont theory,
that the mitochondria and chloroplasts where once heterotrophic prokaryotes andthey were engulfed yet not digested by another cell,
remained there as they were benefitial to the host |
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what genes are found in mtDNA? |
translation tRNA's and rRNA's
structural genes for proteins involved in energy ATP production
thought that mtDNA onbly represents small amount of ancestral DNA, some lost or transferred into nucleus ( nucleus has genes to make mitochondria)
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what genes found in cpDNA? |
chloroplast trranslation
structural proteins for photosynthesis |
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how are mitochondiral and chloroplast DNA transferred ? |
uniparental inheritance ( one parent) usually maternal
example of non-mendelian inheritance |
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what are the rules for non-mendelian inheritance? |
mendelian ratios of segregation not found
reciprocal crosses dont give same results
extranulcear genes cannot be mapped to chromosomes
non-mendelian inheritance not affected by substituting nuclues with different genotype ( cyoplasmic DNA not affected by changing nuclear DNA) |
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how do we know most uniparental cytoplasmic inheritance is maternal? |
in animals all but sperm nuclues destroyed after fertlisation
also eggs have many many more copies of cytoplasmic dna than sperm
eggs are much larger in plants (more copies)
in clamy, minus mating type chloroplasts selectively destroyed by zygote
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what is a leukoplast |
a dysfunctional chloroplast (white-leuk) |
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What is heteroplasmy? |
where individuals with mitochondrial disease have mixture of wild and disesase mitochondria.
proportion of wild and disease give severity, meaning that severtiy can differ between cells and tissue as mitochondria passed on randomly
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1/250 newborns have mutations in mtDNA, but only 1/10,000 adults, why? |
must be a selective pressure that occurs at a younf age that quickly removes diseased mtDNA |
