variation in chromosome number when an organism gains or loses oneor more chromosomes but not a complete set
monosomy: the loss of a single chromosome from an otherwise diploid genome
trisomy: the gain of one chromosome
complete haploid sets of chromosomes are present
polyploidy: more than two sets are present [triploid=3, tetraploid=4, etc]
chromosomes or chromatids fail to disjoin and move to opposite poles during meiosis I or II--> fertilization of abnormal gametes leads to zygotes with three members (trisomy) or only one member (monosomy)
the addition of one or more sets of chromosomes identical to the haploid compliment of the same species
the combination of chromosome sets from different species as a consequence of interspecific matings
when do tetraploids arise?
when chromosomes have replicated and the parent cell fails to divide an d instead enters interphase-- the chromosome number will have duplicated
deletion (or a deficiency)
when a chromosome breaks in one or more places and a portion of it is lost, the missing piece referred to as a deletion
The deletion can occur near one end, ________, or from the interior of the chromosome, ___________.
The deletion can occur near one end, terminal deletion, or from the interior of the chromosome, intercalary deletion.