Cell Division

Question 1

What happens during interphase?

Answer 1

G1: organelles duplicate
Centrioles replicate
Cell growth undertakes to its size

S: Dna is replicated

G2: another growth stage
The duplicated Chromosmes are
checked

Question 2

What are the four stages of mitosis?

Answer 2

Prophase, metaphase, anaphase and telophase

Question 3

What happens during prophase?

Answer 3

The DNA is condensed into chromosomes and they become visible. They shorted and coil.
Spindle fibres form.
Nuclear envelope breaks down.

The spindle fibres join to the centromeres for the chromatids

Question 4

What happens during metaphase?

Answer 4

The spindle fibres align the sister chromatids to the centre of the cell so that both chromatids fave apposite sides

Question 5

What happens during anaphase?

Answer 5

The spindle fibres shorted and pull apart the chromatids so that each half goes to either sides of the cell.

Question 6

What happens during telophase?

Answer 6

The components of the new cells appear.

A new nuclear envelope forms around each of the two groups of chromatids.

This leaves two new cells

Question 7

What is cytokinesis?

Answer 7

The separation of the two cells is cytokinesis. Now there are two cells identical to each other

Question 8

How long does the cell cycle take?

Answer 8

The time taken varies.

For many eukaryotic cells, it take about 24 hours.

Mitosis is only a few short stage in the cell cycle. Interphase is the longest because it takes a very long time to duplicate the DNA and grow the cell to full size.

Question 9

What is the cell cycle?

Answer 9

Cell cycle describes the events that take place as one parent cell divides to produce two new daughter cells which grow to full size.

Question 10

How does meiosis differ from mitosis?

Answer 10

Meiosis produces cells containing half the number of chromosomes

Meiosis produces cells that are genetically different from each other

Question 11

What are haploid and diploid cells?

Answer 11

Haploid cells are cells that contain only one set of chromosomes e.g the daughter cells of meiosis

Diploid cells are cells that contain two sets of chromosomes e.g most eukaryotic cells

Question 12

What are homologous pair of chromosomes?

Answer 12

They are the chromosomes that have come from the mother and the father. They code for the same thing, but are different versions.

For example, two chromosomes that both code for eye colour. But the paternal chromosomes codes for blue eyes, and the maternal for brown eyes.

Question 13

Explain the significance of mitosis for growth

Answer 13

It’s important that cells divide and replace old worn out cells/repair tissues and replicate their duties

Important for growth of tissues. Mitotic division enabled us to grow from conception to multicellular organisms

Important for generic stability and maintaining chromosome number which ensures that our genes are able to carry out its function correctly

Question 14

Define stem cell

Answer 14

Unspecialised cell which is capable of becoming differentiated to a number of different cell types

Question 15

Define differentiation

Answer 15

The development and changes seen in cells of a multicellular organism as they mature to form specialised cells which perform a specific function

Question 16

How can bone marrow differentiate

Answer 16

Bone marrow can become erythrocytes and neutrophils

They are multi potent

Question 17

How have erythrocytes differentiated?

Answer 17

They lose their nucleus, mitochondria, Golgi and RER

They make lots of haemoglobin

Their shape changes to biconcave discs

Function to transport oxygen and co2

Question 18

How have neutrophils differentiated?

Answer 18

They keep their nucleus

They produce granular looking cytoplasm due to many lysosomes produced

Role is to ingest invading microorganism a

Question 19

What are meristem cells

Answer 19

Undifferentiated plant cells capable of rapid cell division

Question 20

What is cambium

Answer 20

A type of meristem cell.

Differentiated to form xylem and phloem

Question 21

How has xylem differentiated?

Answer 21

Meristem cells line up end to end

Their walls become reinforced and waterproofed by lignin

Cell contents die and it become a lone continuous tube with a wide lumen.

Transports water and minerals up the plant

Question 22

How has phloem differentiated?

Answer 22

Meristem line up end to end

Consists of companion cells and sieve tube elements

Sieve tubes allow assimilates to move up and down the plant. They form sieve plates

Companion cells are very metabolically active because they have lots of mitochondria

Question 23

Describe how epithelial cells are specialised

Answer 23

Epithelial tissue covers external and internal surfaces in an animal

Squamous epithelial cells are single thin, smooth layer that lines tubes where diffusion occurs eg alveoli

Ciliates epithelial cells are column shaped cells that cover surfaces. They have tiny projections on their exposed surface called cilia which move mucus

Question 24

Explain the term tissue

Answer 24

A group of cells that are specialised to perform the same function eg epithelial cells

Question 25

explain the term organ

Answer 25

A group of tissues that perform the same particular function. It’s made up of more than a few types of tissues

Eg liver

Question 26

Explain the term organ system

Answer 26

A group of organs which work together to perform a function e.g the reproductive system

Question 27

What is locomotion?

Answer 27

When the muscular, skeletal and nervous system work together to perform a function. It requires a supply of nutrients and oxygen transported using the circulatory system