numerical & structural abnormalities (3) Flashcards
give me 2 examples of events that can cause triploidy
- failure in gametogenesis of one of the meiotic divisions
2. during dispermy (fertilization of a haploid egg by two sperm)
what is the definition of aneuploidy?
Gain or loss of chromosomes equaling less than 1 complete complement
o Usually not inherited but due to meiotic or mitotic nondisjunction errors
explain to me the 3 parts of a nomenclauture chromosome shiz
- The total number of chromosomes
- The sex chromosome complement
- Any chromosome abnormalities
what chromosome is the problem in patau syndrome?
chromosome 13
what are some symptoms assocaited with patau syndrome
much more severe than downs, FTT, “rocker bottom feet”, heart defect
bilateral cleft lip & palate
punched out scalp- missing hair on top of scalp
polydactyly-multiple digits on hands/feet
what chromosome is the problem in edward’s syndrome?
chromosome 18
holla at me some symptoms of edward’s syndrome
Severe muscle hypertonia, low birth weight, VSD, rocker bottom feet
Will not develop the normal milestones of children. Usually don’t talk, walk or potty train. Receding chin
Sloping head
“hand sign” thumb over palm, fingers down and pinky over the fingers
whats the nomenclature of klinefelter syndrome?
47, XXY
what are some symptoms of klinefelter syndrome
tall stature, infertility (prob due to hyalinized testicular tubules, small testicles and azoospermia), some female characteristics may develop (extra fat on hips, breast can develop), learning deficit possible
what are some symptoms of a XYY male?
- Tall stature
* Normal intelligence, normal fertility, clinically indistinguishable from 46, XY
what are the symptoms of XXX females
• Average tall stature, some can have learning issues, some can have fertility problems (but this is uncommon)
what is usually the cause of XXX females?
Usually due to maternal meiosis I error
what is usually the cause of klinefelter patients?
50% due to meiosis I error father
what is the nomenclature for turner syndrome?
45, X
what are some symptoms of turner’s syndrome?
Short, short fingers, neck webbing (due to edema around the neck causing the skin to stretch around the neck which doesn’t return after birth “cystic hygroma”)
Gonadal dysgenesis, primary amenorrhea, usually infertile except for the patients with a X/XX mosaicism
are XY females infertile?
yeah :(
due to lack of any functional internal genitalia
what can result if a pregnant women has CAH
androgens can cross the placenta, so a normal female fetus may develop ambiguous genitalia due to exposure from excess hormones from a CAH affected mother
define mosaicism
presence of at least 2 diff cell lines with at least 1 clear variation between them
is mosaicism acquire or inherited? why?
ONLY can be acquired
this is because you need 2 cells. And a zygote is only 1 cell. So cannot be there
what is a chimera?
2 separate cell lines that eventually fused to form 1 organism
what is a terminal deletion? how many breaks does it require?
deletion that occurs at distal end of 1 arm of a chromosome. This requires only 1 break
what is a intersitial deletion? how many breaks does it require?
internal region of the chromosome is loss. Requires 2 breaks
what chromosome is deleted in wolf hirschlorn syndrome?
short arm of chromosome 4
list some symptoms of wolf hirschlorn syndrome
Microcephaly, micrognathia, hypotonia, epicanthal folds, “starled or surprised expression”, arched brows, long nose with squared off end, short stature, developmental delay (usually end up in special ed)
what is the result of a duplication?
partial trisomy
describe terminal duplications
are usually a direct duplication of the material adjacent to it
describe intersitial duplications
have extra DNA within a chromosome- usually a copy of adjacent regions
are duplications usually sporadic or inherited?
sporadic but could be inherited from parent with benign chromosome rearrangment
if a patient has a balanced translocation and is clinically normal, what can be assumed about their children with the same balanced translocation?
that the children will also be clinically normal
define robertosonian translcations
centromere to centromere translocation involving acrocentric chromosome
which arms fuse in roberstonian translocations? what arms are lost?
long arms fuse, net loss of both short arms
how many chromosomes does roberstonian translocation patients usually have? are they clinically normal?
usually clinically normal but have 45 chromosomes (because 2 of the chromosomes are fused together)
what is more common in robertosian translocations: homologous chromosomes or nonhomologus
nonhomologous but can occur in homologous as well
what are the two fertility problems that can result from a parent with robertosonian homologous translocation
- A cell with a robertsonian translocation (two copies of 21) which if fertilized will give rise to a down syndrome child
- Or a cell with no copies of chromosome 21 which if fertilized will result in monosomy 21 which is not compatible with life
how many breaks are required in a chromosome for an inversion to occur?
at least 2
what type of inversion does the following describe:
“two breaks occur on the same side of the centromere (in the same arm) such that the centromere is not involved in the rearrangement”
paracentric inversion
what type of inversion does the following describe:
“breaks occur on opposite sides of the centromere and the segment reverses order generating a new chromosome with the same genes in a diff order:”
pericentric inversion
for a paracentric inversion, for the chromosomes to pair properly and produce proper gametes, do you want recombination to occur or not occur in the inversion loop
not occur
what two types of chromosomes will occur if there has been recombination in the inversion loop?
- dicentric chromosome- with two centromeres
2. acentric chromosome- no chromosomes
for pericentric inversion, is there an inversion loop?
yes
for pericentric inversion, what is more viable, large inversions or small inversions?
large inversions
