2C GENETICS Meiosis Lesson Disorders
1
Fertilization:
egg and sperm unite to form a
diploid cell
(the tail of sperm disintegrates after chromosomes are delivered)
egg (n) + sperm (n) =
zygote (2n)
Meiosis and Reproduction
Sex chromosomes
= the chromosomes involved in determining gender; the 23rd pair
Autosomes
= the chromosomes not involved in determining gender; pairs 1 through 22
When errors occur in meiosis we can get the wrong number of chromosomes in a cell.
•
a missing chromosome
•
an extra chromosome
Meiosis
Homologous pairs of chromosomes separate & move toward opposite poles of the cell.
Disjunction:
the separation of chromosomes during meiosis.
Nondisjunction:
the failure of homologous chromosomes or sister chromatids to
separate properly
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2C GENETICS Meiosis Lesson Disorders
2
Errors in Meiosis
In mitosis or meiosis, there can be an error in the processes that results in the change in
the number of chromosomes that the daughter cells receive.
There are two types of this error condition:
Monosomy
= having only one copy of a chromosome when you should have a pair.
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- Winter '17
- James Mintz
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