AP BIOLOGY
NAME:____________________________________
DATE:__________________________PER:______
CH. 15: (Part B)
Chromosomes as the Structure of Inheritance
Lecture Notes & Guided Reading
 X Inactivation in Female Mammals
o Recall, mammals (incl.____________), inherit ___ sex chromosomes…
o However, when female mammals (incl____________) inherit 2 ____ chromosomes,
____ X chromosome in each cell becomes almost completely _________________
during ________________ development.
o The inactive X in each cell of a female condenses into a _________ body, a
condensed object that lies inside the nuclear envelope.
o Most of the genes of that X chromosome are ______ expressed.
o In the ovaries, ________ body chromosomes are _______________, so every female
gamete/_________ has an active ____.
 Altering Chromosome # or Structure  can cause Genetic Disorders
o Exceptions to Mendel’s patterns of inheritance, include sex-___________ traits and
gene _______________...
o But also, PHYSICAL & CHEMICAL disturbances, as well as ERRORS during
______________, can DAMAGE chromosomes or ALTER their number in a cell.
o Large-scale chromosomal alterations often lead to spontaneous
_______________/________________ of a fetus, & individuals born with these types of
genetic defects commonly exhibit various developmental _______________.
o These genetic defects are more significant in ______________ than in ____________.
 ABNORMAL CHROMOSOME #:

NONDISJUNCTION: when the members of a pair of ________________
chromosomes do ________ move apart properly during ____________ ___, or sister
chromatids fail to separate during ____________ ___. (SEE FIG.15.12 pg.285)
 Causes 1 gamete to receive 2 of the same type of chromosome & another
gamete to receives no copy of the chromosome.
-1-
 ANEUPLOIDY: a chromosomal
_______________ in which one or
more chromosomes are present
in extra copies or are deficit in
number.

MONOSOMY: when an
aneuploidy cell is
_____________ ____
chromosome for a particular ________________ pair.

TRISOMY: when an aneuploidy cell has ____ ____________ chromosome
for a particular __________.
 POLYPLOIDY: a chromosomal alteration in which an organism possesses more
than ____ complete ________ of chromosomes.

TRIPLOIDY: __________________________________________________________

TETRAPLOIDY: ______________________________________________________
 ALTERATIONS of CHROMOSOME STRUCTURE:
o Breakage of a chromosome can lead to ____ types of changes in the chromosome
structure: (see FIG. 15.14 pg.286)

DELETION

DUPLICATION

INVERSION

TRANSLOCATION
 DELETION: occurs when a chromosomal fragment lacking a centromere is lost.
o Removes a segment of the chromosome; can result in missing __________.
o Can cause severe problems, i.e. syndrome “cri du chat”
-2-
 DUPLICATION: occurs during ___________, when a deleted fragment re-attaches
as an extra segment
o Results in a ______________ segment.
 INVERSION: when a chromosomal fragment re-attaches to its original
chromosome, but in the _____________ orientation (backwards).
 TRANSLOCATION: when a fragment joins a nonhomologous chromosome.
o “translocates” = __________ ______________
o Can cause certain types of _____________, i.e. chronic myelogenous leukemia
(CML), where a large portion of chromosome 22, the _________________
chromosome exchanges with a small fragment tip of chromosome ____.

DELETIONS & DUPLICATIONS are common during ______________.
 Human disorders can result from CHROMOSOMAL ALTERATIONS:

If an ANEUPLOID GAMETE combines with a normal gamete, the zygote is
_______________, and usually spontaneously aborts due to significant embryonic
development problems.

Some of these syndromes can survive to birth and live full lives:
o Trisomy 21/_________ ______________: have an extra _________________
______, & a total of ______ chromosomes.
o ANEUPLOIDY of SEX CHROMOSOMES: (_________ “problematic”)

Having extra Y chromosome: ________________________________________

Having extra X chromosome: ________________________________________