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Meiosis I

What is unique about the first round of Meiosis? The first cell division in Meiosis is known as Meiosis I. The function of Meiosis I is very different from that of either Mitosis or Meiosis II. In both Mitosis and Meiosis II sister chromatids are separated during anaphase to produce identical daughter cells. In Meiosis I members of homologous chromosome pairs are separated. This results in the segregation of genes into the two gametes. The principle of segregation is one of two core ideas in genetics proposed by Gregor Mendel. The segregation of any one pair of chromosomes is independent of any other pair. Assortment of chromosomes from each pair to the two daughter cells is random. The number of possible genetic combinations in the resulting gametes is therefore very large.

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

1Which of the following events occur during prophase I?
A)breakdown of nuclear envelope
B)condensation of chromosomes
C)movement of centrosomes
D)A and B
E)A, B and C

2How many bivalents are formed in a cell with 20 chromosomes at the beginning of meiosis I?

3Which of the following events occur during anaphase I?
A)separation of homologous chromosomes
B)formation of synaptonemal complex
C)lengthening of kinetochore microtubules
D)A and B
E)A, B and C

4At the end of meiosis I, there are two haploid cells, each with two sister chromatids per chromosome.

5The period between meiosis I and II is termed interkinesis.

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