Answers amoeba sisters: video recap meiosis1. interphase must occur before meiosis can happen. what would happen is interphase didn't occur first? 2. a cell that begins meiosis has 23 chromosomes inherited from the mother and 23 chromosomes inherited from the father. in the process of meiosis, chromosomes begin to match up in homologous pairs. how would you know if two chromosomes were homologous? 3. crossing-over is a very important event in prophase i of meiosis! what happens during crossing over and what is the significance? 4. meiosis does pmat twice! that means there is a prophase i and ii. there is a metaphase i and ii, etc. if the cartoon below has chromosomes in the middle of the cell, how should you know whether it was in metaphase i or ii? 5. meiosis does not always occur without any difficulties. describe what occurs during nondisjunction and the effect on the resulting cells.

1.Interphase is an important and the longest phase of the cell cycle during which the cell prepares for division by coping its DNA. It is metabolic phase of the cell, in which the cell grows, obtains nutrients and metabolizes them. There are three stages of interphase: G1 (the cell growth), S (replication of DNA, chromosomes are copied) and G2 (preparation for division). Without this phase, genetic material wouldn’t be ready for the process of meiosis  and haploid gametes couldn’t be created.

2.Homologous chromosomes are the similar but not totally identical chromosome pairs that an organism receives from its two parents. During the prophase I of meiosis they pair up: each chromosome aligns with its homologue partner via link-chiasmata ( the two match up at corresponding positions). Those homologue pairs separate during a first stage of cell division (meiosis I-reduction of chromosomes number, from diploid to haploid), while sister chromatids separate during a second stage (meiosis II).

3.Crossing over is a process in which homologous chromosomes trade their parts. Crossing over is process of genetic recombination where DNA is cut and then repaired. Cut and repair of homologous chromosomes allow them to exchange some of their genetic information. As a consequence of crossing over, new arrangement of maternal and paternal alleles on the same chromosome is achieved. It is the way to create varations.

4.During the metaphase I, homologue pairs are lined up comparing to metaphase II where individual chromosomes are lined up. It is because during the meiosis I homologue pairs separate and chromosome number reduce from diploid to haploid. On the other hand, during the meiosis II, sister chromatids separate.

5.Nondisjunction is the consequence of cell division, where there is no properly separation. There are  different forms of nondisjunction:  

•failure of a pair of homologous chromosomes to separate in meiosis I,  

•failure of sister chromatids to separate during meiosis II.

After nondisjunction, resulting daughter cells are with abnormal chromosome numbers -aneuploidy.

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