mitosis

Question 1

Mitosis

Answer 1

Process by which the nucleus divides to form two genetically identical nuclei

Question 2

When does mitosis occur?

Answer 2

• During growth
• during embryonic development, when the large cell produced by fertilization (zygote) divides repeatedly to produce many smaller cells (stem cells)
• When tissues have been damaged and need to be repaired
• To reproduce asexually

Question 3

Are skin cells healing injuries considered reproduction?

Answer 3

Skin cells to heal injuries are not reproduction —> it’s producing new cells but NOT NEW ORGANISMS

Reproduction is only used for increasing number of organisms

Mr. D’s cells are dividing by mitosis

Question 4

Is Bacteria splitting by mitosis reproduction?

Answer 4

Bacteria splitting by mitosis is reproduction as the number of bacteria/organisms is increasing through asexual reproduction.
Specially called Binary Fission.

Question 5

Cell Cycle Definition

Answer 5

All the stages between one cell division and another

Question 6

Gamete Definition

Answer 6

Organ’s reproductive cells

Question 7

What occurs during the G1 phase?

Answer 7

• The cell grows and functions normally undergoing everyday processes.
• Rapid protein synthesis takes place allowing the cell to grow in size.
• Proteins required for DNA synthesis (the next phase) are made.
• Mitochondria and chloroplasts (in the case of plant cells) are replicated. This also continues in S phase.

Question 8

What occurs during the S phase?

Answer 8

The amount of DNA doubles as DNA replication takes place.

The genetic material is duplicated but no chromosomes are formed yet.

Question 9

What occurs during the G2 phase?

Answer 9

Protein synthesis occurs to produce the proteins needed for cell division, such as microtubule proteins that will make up a mitotic spindle. The cell is actively preparing for cell division.

Question 10

Histones

Answer 10

are basic (alkaline) proteins that form part of nucleosomes.

Question 11

Prophase

5 things occur

Answer 11

• DNA supercoils causing the chromatin to condense.
• Nucleolus disappears.
• Nuclear membrane disintegrates.
• Spindle fibres (made of microtubules) start to form (and are completely formed by the end of prophase).
• Centrioles (absent from plant cells) move to opposite poles.

Question 12

Metaphase

2 things occur

Answer 12

• Spindle fibres bind to the centromere of sister chromatids and cause their movement towards the equatorial plate.
• Sister chromatids are aligned at the equatorial plate at the end of metaphase.

Question 13

Anaphase (the shortest phase of mitosis)

Answer 13

-Sister chromatids are separated (now known as chromosomes) and pulled to opposite poles by the spindle fibres.

Question 14

Telophase

6 things occur

Answer 14

• The chromosomes have reached the poles.
• A nuclear membrane starts to reform at each pole.
• A nucleolus appears in each new nucleus.
• The spindle fibres disintegrate.
• The cell elongates in preparation for cytokinesis.
• In some cases, the invagination of the membrane is also visible (marking the beginning of cytokinesis).

Question 15

Mitotic index Definition

Answer 15

The mitotic index is defined as the ratio of the number of cells in a population undergoing mitosis (prophase, metaphase, anaphase or telophase) to the total number of visible cells.

Question 16

Mitotic Index Equation

Answer 16

Mitotic index=P+M+A+T/Total cells

Question 17

Describe chromosomes at the different stages

Answer 17

Sister chromatids are created during the S phase when DNA replication occurs. The two chromatids are identical and are joined by a centromere.
After anaphase, the sister chromatids separate at the centromere and at this point they are referred to as chromosomes.

Question 18

Spindle Fiber

Answer 18

protein cable which grabs the chromosome to puts it in the right place (coming out of the centriole)

Question 19

Cyclins

Answer 19

Cyclins are a family of proteins that control the progression of cells through the cell cycle.

Question 20

Importance of Cyclins

Answer 20

Cells cannot progress to the next stage of the cell cycle unless the specific cyclin reaches a certain concentration.

Question 21

What enzyme do cyclins bind to?

Answer 21

Cyclins bind to enzymes called cyclin-dependent kinases (CDKs) and activate them. The activated CDKs then attach phosphate groups (phosphorylation) to other proteins in the cell. The attachment of phosphate triggers the other proteins to become active and carry out tasks

Question 22

G1 phase Cyclin

Answer 22

During this phase cyclin D (red line) levels gradually increase.

Question 23

S Phase Cyclin

Answer 23

Cyclin E (purple line) is instrumental to DNA replication and also promotes centromere duplication.

Question 24

G2 phase Cyclin

Answer 24

Cyclin A (blue line) helps induce DNA replication.

Question 25

Mitosis Cyclin

Answer 25

Cyclin B (yellow line) is essential for the formation of mitotic spindles and the alignment of chromatids.