Chromosomal Aberations Flashcards
Errors in meitoic chromosome segregation leads to ..
Whole chromosome aneuploidy
Two possible causes of Chromosomal aberration
defects to chromosome segregation and DNA damage repair
Error in DNA damage repair can lead to ..
chromosomal aberrations: structural variation
- affects a large region of DNA, but not entrie chromosome
- can involve one or more chromosomes, and includes copy number variants (CNVs) and rearrangements
Down syndrome (3 copies of chromosome 21) is an example of
whole chromosome aneuploidy, trisomy
when paired chromosomes (meiosis I) or sister chromatids (meiosis II) fail to separate
Nondisjunction
nondisjunction during meiosis can lead to production of … germ cells which is a (deviation from the normal haploid number of chromosomes) which can result in trisomy or monosomy at fertilizaiton
aneuploid
whole chromosome aneuploidy is caused by ..
Nondisjunction events
chromosome analysis test that evaluates the number of a persons chromosome in order to detect abnormalities
- chromosomes are fixed & stained
- from Metaphase cells (bc gm is condensed)
- can detect large aneuploides or rearrangements
Karyotype Analysis
the occurance of one or more extra or missing chromosomes leading to an unbalanced chromosome complement, includes monosomy and trisomy
Aneuploidy
used to describe the absence of one member of a pair of chromosomes
Monosomy
used to describe the presence of an extra chromosome, add 1
ex: down syndrome
Trisomy
Presence of a set of extra chromosomes, adding 23 to 46
Triploidy
The loss of one set of chromosomes, 46-23 = 23
Monoploidy
Monoploidy and Triploidy are NOT considered …
Monosomy and Trisomy are considerered..
Aneuploidy
Most whole chromosome aneuploidies are lethal, what are execptions (5)?
Patau syndrome (trisomy 13) Edwards syndrome (trisomy 18) - result in live birth, few survive after 1 year Down syndrome (trisomy 21) Turner syndrome (XO) (monosomy of X chrome) Klinefelter syndrome (XXY) males w extra X
Nondisjunction during meiosis I produces … aneuploid gametes. Nondisjunction during meiosis II produces .. aneuploid gametes.
Four, two
Structural variation that Involves only a single chromosome
CNVs: deletions and duplications on a chromsome
Rearrangements: Inversion (flipping/inverting a portion of chromosome)
intrachromosomal variation
structural variaiton that involves multiple chromosomes
CNVs: unbalanced translocation (unidirectional transfer of genetic material)
Rearrangements: Balanced translocation (material exchanged bt 2 chromosomes)
Interchromosomal
An increase/decrease in the number of the copies of some portion of the genome. (involves deletions/duplications of dna) and unbalanced translocation (where DNA is gain/lost)
CNV copy number variant
During .. chromosomes are moved around, but you do not loose any genetic material (no chnage in copy number), but you can disrput the gene and can lead to issues with the next meiosis
Rearrangements
… analysis can be used to detect chromosomes such as in normal diploid cells, trisomy/monosomy, deletions/duplications, and translocations
Karyotype
This analysis can be used to detect aneuploidies or rearrangements of any size - more specificity.
- DNA stained with DAPI dye
- used on metaphase or interphase cells
- can be done fast, but need to be confirmed by karyotype
- can look at very specific regions of DNA
FISH Analysis
In a diploid cell, a FISH probe will bind to the same sequence on both homologous chromosomes. In metaphase FISH, DNA replication will have occurred and the chromosomes will be condensed, so you will be able to detect a signal on each of the sister chromatids, or ….. signals in total. In interphase FISH, DNA replication has not yet occurred and you will see just …. signals.
four, two
Exchange of genetic material between two chromosomes (interchromosomal) which does not cause a gain or loss of any material
A balanced translocation
Exchange of genetic material between two chromosomes (interchromosomal) which does cause a gain or loss of any material
An unbalanced translocation
glass slides spotted with many different DNA probes that can be tiled across the genome (corresponds to genome)
Microarray
Microarray :
bloodwork -> patient DNA -> fragment and label -> anneal (binds) to microarray probes
* DNA carries dye so when bound it lights up
* measuring fluorescence can show DNA bound
What is the microarray used to detect? and Why?
microarray is type of genotyping used to measure expression level of large amount of genes
CNVs (gain/loss of DNA)
bc you can look across the genome at the signal of the labelled DNA - can be interpreted to identify CNVs
* signal increases with a duplication
* signal decreases with deletion
