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Deletion;
refers to the absence of a portion of a chromosome; it results from breakage and falling off of a
portion of a chromosome; leading to loss of a group of genes that may have a disastrous effect
on the development of an organism;
Inversion;
refers to reversal of normal sequence of genes in portion of a chromosome; occurs when a
middle portion of a chromosome breaks, turns or rotates (inverts) through 180o and joins up
again; this does not change the genetic constitution of the organism; but may bring into close
proximity genes whose combined effects to an organism produce a beneficial effect to an
organism; or cause disadvantages to the organism;
Translocation;
attachment of a portion of a chromosome to a non-homologous chromosome; occurs when a
chromosome breaks and the portion joins another non-homologous chromosome; this may
lead to serious consequences, even death depending on what genes are missing;
Duplication;
situation where a set of genes is represented twice in a chromosome; a part of a chromatid
formed during cell division may replicate further to form an extra piece; which may attach
onto the same or another chromatid; resulting to traits controlled by some genes being
excessively expressed;
Non-disjunction;
this is failure of a pair of homologous chromosomes to separate during the first stage of meiosis;
resulting in one of the daughter cells formed after division of the cell having two of one kind of
a chromosome; while the other cell has less or none; diseases or disorders known as syndromes
are known to result from this aberration e.g. Down's Syndrome (Mongolism),Turner
Syndrome, Klinefelter Syndrome;
Polyploidy;
this is the presence of more than two sets of chromosomes in a cell; occurs due to a failure of a
cell to divide after the first stage of meiosis or after the chromosomes have replicated in mitosis;
common in plants than animals; in plants, it causes some improvements such as resistance to
drought, certain diseases and pests, improved yields and early maturity;
Kavungya answered the question on May 13, 2021 at 14:13
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