Chapter 10 - Eukaryotic chromosome Abnormalities and organization Flashcards
Process for creating a chromosome spread?
1 - sample white blood cels, treat with a solution to cause dividing
2 - use colchicine to disassemble microtubules,
3 - add to chambered slide in a hypotonic solution to cause swelling
4 - centrifuge cells, cells explode
5 - arrange chromo spread
What is the FISH test?
Flourescent In-Situ hybridization
maps genetic material in human cells
What is g-banding
- displays condensation levels of Euchromatin and heterochromatin in order to determine a deletion/duplication in genes
What is euchromatin ?
transcriptionally active chromatin
displays a light stain on g-band test
decondenses in interphase
what is heterochromatin?
transcriptionally inactive chromatin
darker band
stays condensed
What are the types of heterochromatin?
Constitutive - areas of the chromosome that are always condensed
———-centromere: contins structural DNA, no genes, remains condensed
———–Telomere - remain condensed
Facultative - sometimes…
———-tissue specific and or developmental stage specific
What is euploid?
Euploid is having an equal number of copies of each gene on all chromosomes, even if this is not the wild type number
what is aneuploid, and what effect does it have on the gene dosage?
Unequal number of copies of each gene on all chromosomes
gene dosage is off… causes many problems
ex: trisome 13
What causes aneuploidy?
Non disjunction
Result of nondisjunction in meisos I?
all aneuploid ( trisomic, monosomic)
result of nondisjunction in Meiosis II?
50% aneuploid (25% trisomy, 25% mono)
50% euploid
Three examples of autosomal aneuploidy
trisomy 13 - patau syndrome
trisomy 18 - edward syndrome
trisomy 21 - down syndrome
four examples of sex-chromosome aneuploidies
47, XXY - klinefelter, M
47 XYY - jacob syndrome, M
47 XXX - triple X, F
45 XO - turner , F
Describe mosaicism
Mosaicism is when 46, XX (wild type) experience non disjunction in meiosis, yielding 46 XX (wild type) and 45 XO/ 47 XXX, which are all included int he karyotype
Describe uniparental disomy
Uniparental disomy is when both homologs are passed from one parent
how does a uniparental disomy occur
nondisjunction of the same chromosome in both sperm and egg
nondisjunction in one parent –> aneuploid gamete
———trisomy rescue
what is a trisomy rescue?
- one chromosome randomly gets kicked off
What are the type of polypoidy?
autopolypoloidy - chromosomes from the same species (plants, sometimes we do on purpose (genetic modified food)
allopolyploidy - chromosomes from different species
What determines if a species is fertile?
Even number of gametes = fertile
odd number = not fertile
ex: horse (64) x donkey (62) = mule (63)
Describe a terminal deletion
- partial deletion of a chromosome, lost in cell division
- length missing depends on if organism is viable or not
describe interstitial deletion
- many small deletions within p or q arms
-tests can be done to detect these deletions if symptoms arise
Describe a duplication
extra genetic material
unpaired loops caused by chromosomes trying to line up and pushing duplicated portion out
What does detection of a deletion/duplication look like in a FISH test?
Wild type - FISH probes A…(centro)…BC
Deletion - A…(centro)……C
duplication - A….(centromere)…BBC
describe unequal crossing over?
1 - PMSa and PMSb misalign, a copy of PMS on each chromo loops out, unequal crossing occurs…
2 - recombinations:
deletion missing the 17 genes between PMS duplicates
duplication with PMS a and b, hybrid gene and duplication of the 17 genes
