Biology, Eighth Edition (Raven)

Chapter 11: Sexual Reproduction and Meiosis

Random Orientation of Chromosomes During Meiosis

How does independent assortment of chromosomes operate during meiosis? In Meiosis I members of homologous pairs separate during anaphase. The separation of each pair is random with respect to all the other pairs. For each pair there is a maternal and a paternal chromosome which came from the mother and father respectively. There is no mechanism to cause maternal or paternal chromosomes to either associate with or repel one another. Therefore the orientation of each chromosome pairs is random with respect to other chromosome pairs. This is necessary for the independent assortment of genes, an important principle of genetics. It also allows for gametes, and thus offspring, to be much more genetically variable than they would be if all the paternal and maternal chromosomes were inherited as a unit.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

Random orientation of homologous chromosomes occurs in ________ of meiosis.
A)prophase I
B)metaphase I
C)anaphase I
D)prophase II
E)metaphase II
2.

Consider a cell that has four pairs of chromosomes. What is the number of possible chromosome orientations in that cell?
A)4
B)8
C)16
D)24
E)32
3.

Consider a cell that has three pairs of chromosomes. What fraction of the gametes produced from this cell will contain only maternal chromosomes?
A)1/2
B)1/4
C)1/6
D)1/8
E)1/12
4.

The region of the cell where chromosome pairs line up is referred to as the plate.
A)True
B)False
5.

The actual structure that homologues bind to is called the spindle axis.
A)True
B)False
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