BIOL 1113 Lecture Notes - Lecture 5: Triticale, Polyploid, Gamete
Document Summary
7% of chromosomes are in some way functional. Ways for cellular division to go wrong: non-disjunction: failure of all chromosomes to separate, polyploid progeny; e. g. , triploid if 1 extra set of egg or sperm, failure of 1 pair to separate, trisomy: progeny have, monosomy: ___ Plants usually tolerant: polyploid plants include >1 species (e. g. , triticale from wheat & rye) Animals usually very intolerant: almost always ends in death. In humans, autosomes (=all chromosomes except x and y) require proper balance (i. e. , not too few or too many) Monosomies & most trisomies: death, exceptions: trisomy 21 (down syndrome) X and y chromosomes in us (& other mammals) can be present in wrong #, usually with no or few effects. = mammalian mechanism for dealing with excess x chromosome. Since normal females xx, built-in genic imbalance. 1 x inactivated dark blob in nucleus = barr body in every female cell, so females & males have equal amount of active x.
