Meiosis

Question 0

Prophase I

Answer 0

• first phase of meiosis I
• chromosomes coil up and spindle fibers form
• as chromosomes coil, homologous chromosomes line up to form a four part structure called a tetrad
• a tetrad consists of two homologous chromosomes, each made up of two sister chromatids
• crossing over (arms of non-sister chromatids wind around each other and exchange genetic material) occurs; and average of 2-3 crossovers occur for each homologous chromosome

Question 1

Interphase

Answer 1

• cell replicates its chromatin

- each chromosome consists of two identical sister chromatids held together by a centromere

Question 2

Metaphase I

Answer 2

• second phase of meiosis I

- centromere of each chromosome becomes attached to spindle fiber and pull tetrads into middle of spindle

Question 3

Anaphase I

Answer 3

• third phase of meiosis I
• homologous chromosomes, each with its two chromatids, move to opposite ends of the cell
• centromeres holding sister chromatids do not spilt, ensuring that each new cell only receives one chromosome from each homologous pair

Question 4

Telophase I

Answer 4

• fourth and final phase of meiosis I
• spindle breaks down, chromosomes uncoil, and cytoplasm is divided to yield two new cells
• each cell has half the genetic material of the original cell because it has only one chromosome from each homologous pair

Question 5

Prophase II

Answer 5

• first phase of meiosis II (fifth phase of meiosis)

- spindle forms in each of the two cells and spindle fibers attach to the chromosomes

Question 6

Metaphase II

Answer 6

• second phase of meiosis II (sixth phase of meiosis)

- chromosomes, still composed of sister chromatids, are pulled to the center of the cell and line up at the equator

Question 7

Anaphase II

Answer 7

• third phase of meiosis II (seventh phase of meiosis)

- centromere of each chromosome splits, allowing the sister chromatids to separate and move to opposite poles

Question 8

Telophase II

Answer 8

• fourth and final phase of meiosis II (eighth and final phase of meiosis)
• nuclei reform, spindle breaks down, and cytoplasm divides
• four haploid cells have been formed from one diploid cell
• each haploid cell contains one chromatid from each homologous pair