Chapter 2 - Mitosis And Cells

Question 1

What is mitosis?

Answer 1

The stage of the cell cycle where the cell divides into two identical cells

Question 2

Why do multicellular organisms use mitosis?

Answer 2

To grow

To replace cells that have been damaged

Question 3

Why might single-celled organisms use mitosis?

Answer 3

To reproduce - asexual reproduction.

Question 4

What is another name for the process of mitosis?

Answer 4

Cloning

Question 5

What happens during interphase?

Answer 5

The cell increases the amount of subcellular structures like mitochondria and ribosomes. It then duplicates it DNA - it is copied and form X-shaped chromosomes. Each ‘arm’ is an exact duplicate of the other

Question 6

Name the stages of mitosis

Answer 6

Prophase, Metaphase, Anaphase, Telophase

Question 7

What happens during prophase?

Answer 7

The chromosomes condense, getting shorter and wider. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm.

Question 8

What happens during metaphase?

Answer 8

The chromosomes line up down the center of the cell

Question 9

What happens during anaphase?

Answer 9

Cell fibers pull the chromosomes apart. The two arms of each chromosomes go to opposite ends of the cell.

Question 10

What happens during telophase?

Answer 10

Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells. The nucleus of the cell has divided

Question 11

What happens during cytokinesis?

Answer 11

Before telophase ends, the cytoplasm and cell membrane divide to form two separate cells.

Question 12

What are the processes in which plants and animals can grow and develop?

Answer 12

Cell differentiation, cell division - by mitosis and also cell elongation

Question 13

What is cell differentiation?

Answer 13

The process by which a cell changes to become specialised for its job

Question 14

What is cell elongation?

Answer 14

Where a plant cell expands, making the cell bigger and so making the plant grow

Question 15

How do animals grow and develop (in terms of cells)?

Answer 15

By cell division. When they are young, their cells divide at a fast rate but once they stop growing/reach adulthood, most is for repair. Differentiation is lost at an early stage

Question 16

How do plants grow and develop (in terms of cells)?

Answer 16

Growth in height is usually due to cell elongation. Cell division usually just happens in the roots and shoots. Plants often grow continuously therefore plants continue to differentiate to develop new parts (e.g. leaves, roots)

Question 17

What is cancer and how is it caused?

Answer 17

The rate at which cells divide by mitosis is controlled by genes in the DNA. A mutation could cause the cells to start dividing uncontrollably. This can result in a tumor (a mass of abnormal cells) - if it invades and destroys surrounding tissue it is called cancer.

Question 18

What are stem cells?

Answer 18

Undifferentiated cells. These embryonic cells have the potential to divide by mitosis and then differentiate to produce any kind of cell.

Question 19

Where are stem cells found?

Answer 19

In early human embryos. They are found in only a few places in adults like bone marrow. They are then no longer as versatile as embryonic ones and can only produce certain ones. In animals, adult stem cells are used to replace damaged cells like skin or blood cells.

Question 20

What are the three types of stem cell called?

Answer 20

Totipotent - e.g. embryo (can grow anything)
Pluripotent - can grow lots of things
Multipotent - e.g. bone marrow (can only grow a few things)

Question 21

What are somatic cells?

Answer 21

Body cells where mitosis occurs. But there are exceptions such as gametes and brain cells (form by mitosis but don’t replicate after) form by mitosis but aren’t body cells. Bacteria also replicate by mitosis but are first formed asexually, unlike somatic cells which their DNA is first formed sexually (2 sets of DNA)

Question 22

What makes scar tissue?

Answer 22

Particularly in young people, mitosis occurs quickly to cover cuts so form scars

Question 23

Name some advantages of being multicellular

Answer 23

Innate redundancy capacity, cells can die but you will still survive as there are more of them so you are harder to kill
Complex, protects cells easily as cells are more efficient at their specific job

Question 24

What is diploid? What type of cell

Answer 24

A cell with 2 sets of chromosomes

Question 25

What is haploid? Give an example of this in humans

Answer 25

Cells with one set of one chromosomes, such as gametes

Question 26

When is the S Phase and what happens in it?

Answer 26

It occurs in the S phase of interphase and is when DNA is replicated (which must be done carefully to avoid abnormalities that could cause serious damage). It is between the 2 G checkpoint phase of interphase, which takes a while compared to mitosis in general