PSIO (469) FINAL Flashcards
what is Mosaicism?
Single zygote- individual has presence of two or more genetically different cell lines but developed from a single zygote.
what is chimerism?
Different zygotes- individual has presence of two or more genetically distinct cell populations derived from different zygotes.
what is it called when two or more embryos fuse together during early development, leading to a single individual with cells from each original embryo?
chimeric organism
what is the result of errors during meiotic or mitotic cell division?
Mosaicism organismw
what is the difference between Meiotic non-disjunction and Mitotic non-disjunction?
Meiotic non-disj = homologous chromosomes or sister chromatids remain together, result is one extra copy of 1 chromosome in egg.
Mitotic non-disj = sister chromatids remain together, result is 1 extra copy of 1 chromosome (trisomy) in daughter cell.
what is anaphase lag or trisomy rescue?
It corrects trisomy but results in mosaicism
what percent of embryos develop into mosaicism organisms?
15-90% at two-to-eight cell stage, 16-33% at blastocyst stage
what two tests can be done to check for mosaicism in pregnancy?
chorionic villus sampling (CVS) done ~10-12 weeks.
Amniocentesis done ~16-18 weeks.
what is the difference between Euploid and Aneuploid?
Euploid is the normal cell with the normal set of chromosomes, while Aneuploid is a cell with abnormal number of chromosomes.
why does mosaicism pose a concern for preimplantation genetic testing (PGT)?
biopsy may not capture cells with abnormal genetic makeup leading to false-neg results. If PGT doesn’t accurately detect mosaicism there is a risk of transferring embyros with chromosomal abnormalities to the uterus.
what is the difference between WGS and WES?
WGS is whole genome sequencing which sequences the entire genome of an individual. WES is whole exon sequencing which sequences only the protein-coding regions of the genome (exons)
what are some arguments in favor of PGT?
decreased termination due to aneuploidy, increased preg rates, reduced miscarriage rates.
what is congenital defect?
any physical anomaly which is recognizable at birth
what are examples of single gene defect?
Achondroplasia, cystic fibrosis, hemophilia.
what is chromosomal defect?
too many or too little chromosomes (aneuploidy)
what is it called when environmental substances cause birth defects?
Teratogen
how much folic acid is recommended for pregnancy?
400mcg or 40mg
why does folic acid play a big role?
it plays a role in the formation of neural tube, which develops into the baby’s brain and spial cord during early weeks of pregnancy.
during what days of pregnancy does the neural tube form?
between days 15-18 counting from fertilization
what are two neural tube defects?
Anencephaly and Spina Bifida
what is it called when the upper neural tube does not close all the way. Baby is born without parts of brain and skull?
Anencephaly
What is it called where anywhere along spine where lower part of neural tube does not close all the way and causes physical and mental disabilities that range from mild to severe?
Spina Bifida
what does NIPT stand for and what is it?
NIPT = Non-Invasive Prenatal Testing. It is done as early as 7 weeks, and it analyzes cell free DNA circulating in the mother’s bloodstream. It can screen for certain genetic conditions caused by extra or missing pieces of DNA.
what is the test called where it can analyze the small amount of fetal DNA present in mother’s blood?
Cell Free Fetal DNA