Cytogenetics- General

Question 1

Polyploidy: Etiology: Fates:

Answer 1

Polyploidy: more than 2 COMPLETE sets of chromosomes Etiology: polyspermy- two sperm fertilizing the same egg Fates: Spontaneous abortion, partial hydatidiform mole (choriocarcinoma) or can persist to term but has 100% post natal mortalilty

Question 2

Aneuploidy: causes:

Answer 2

Aneuploidy: an abnormal number of one set of chromosomes monosomy: one homolog of a chromosome (Turner X0) trisomy- three homologs of a chromosome (trisomy 21, downs syndrome) caused by non-disjunction during the meiotic anaphase

Question 3

Balanced Aberration definition:

Answer 3

Balanced Aberration: 1) no essential chromosomal material is lost 2) no breakpoints are within an essential gene 3) no gene is moved away from its promoter or enhancer to another regulatory region **balanced translocations are silent in carriers because no chromosomal material is lost, but their progeny may or may not be affected)

Question 4

Reciprocal translocation:

Terminal Translocation:

Answer 4

A reciprocal translocation is balanced in the parent but an lead to a duplication or deletion in the progeny

A terminal translocation is a balanced abberation created by a DNA ligase error in the parent and can lead to a partial trisomy after fertilization