Topic 3 - Lesson 5

Question 1

Interphase

Answer 1

New cell organelles are synthesized and DNA replication occurs which results in enough cell contents to produce two new cells

Question 2

Prophase

Answer 2

Chromosomes condense and become shorter and thicker, each one visible as two strands called chromatids. Sister chromatids are identical (apart from any mutations) produced by replication. Centrioles position at opposite sides of the nuclear envelope. Spindle fibers form between the two centrioles

Question 3

Metaphase

Answer 3

Nuclear envelope breakdown. Chromosome’s centromeres attach to spindle fibers at the equator

Question 4

Anaphase

Answer 4

Centromeres split. Spindle fibers shorten, pulling the two halves of each centromere in opposite directions. One chromatid of each chromosome pulled to each pole. Spindles break down once separated chromatids reached poles

Question 5

Telophase

Answer 5

Chromosomes unravel, Nuclear envelope reforms. Two sets of genetic information enclosed in separate nuclei

Question 6

Cytokinesis

Answer 6

Cytoplasmic division, Surface membrane contracts until the cell is divided into two new cells. In plant cells, instead of this constriction, a new plate is synthesized between the two new cells. The plate becomes a new cell wall

Question 7

Example Answer

Answer 7

During the cell cycle, most of the time is spent during interphase. During this phase, the cell will replicate its DNA and copy its organelles. The part of the cell cycle when the cell divides is called mitosis. Mitosis is broken into 4 stages. These can be remembered using PMAT. This first stage is prophase. During this stage the chromosomes condense and become visible. The nuclear envelope starts to disappear. Next, during metaphase, the chromosomes line up along the equator. Spindle fibers start to form and they attach to the middle of the chromosome, called the centromere. During anaphase, the spindle fibres contract and pull the chromosomes apart into chromatids. Each chromatid moves to opposite poles of the cell. The final stage is called telophase. The nuclear envelope reforms around the chromosomes at either side of the cell. The cytoplasm then divides during cytokinesis and two identical daughter cells are produced.

Question 8

Mitotic Index

Answer 8

Cells in mitosis/ total number of cells