Cell Division and Cellular Organisation

Question 1

Gap phase 1

Answer 1

Cell grows and new organelles and proteins are made

Question 2

What are the main phases in the cell cycle?

Answer 2

• M Phase (mitosis and cytokinesis)
• G1 (gap phase 1)
• Synthesis
• G2

Question 3

Gap phase 2

Answer 3

Cell keeps growing and proteins needed for division are made

Question 4

Synthesis

Answer 4

Cell replicates its DNA, ready to divide by mitosis

Question 5

G2 checkpoint

Answer 5

The cells check whether all the DNA has been replicated without any damage. If it has then cell can divide by mitosis

Question 6

G1 checkpoint

Answer 6

The cell checks that the chemicals needed for replication are present and for any damage to the DNA before entering S phase

Question 7

What is mitosis needed for?

Answer 7

• Growth in multicellular organisms as well as repairing damaged tissues.
• Also a method of asexual reproduction for some plants, animals and fungi

Question 8

What comes before mitosis in the cell cycle?

Answer 8

-Interphase

Question 9

Describe what happens in Interphase

Answer 9

• The cell carries out normal functions, but also prepares to divide
• The cell’s DNA is unravelled and replicated, to double it’s genetic content.
• Organelles are also replicated so it has spare ones, ATP content is increased

Question 10

What are the four stages of mitosis?

Answer 10

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 11

Describe prophase?

Answer 11

• Chromosomes condense, getting shorter and fatter.
• Centrioles start moving to opposite ends of the cell, forming a network of protein fibres (spindle)
• The nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 12

Centrioles

Answer 12

-Tiny bundles of protein

Question 13

Describe metaphase?

Answer 13

• The chromosomes (each with 2 chromatids) line up along the middle of the cell and become attached to the spindle by their centromere.
• At the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue

Question 14

Describe anaphase?

Answer 14

• The centromeres divide, separating the pairs of sister chromatids.
• The spindle contracts, pulling th chromatids to polar ends of the cell, centromeres first

Question 15

Describe telophase?

Answer 15

• Chromatids reach polar ends of the cell on the spindle.
• They uncoil and become long and thin again.
• Now called chromosomes again
• A nuclear envelope forms around each group of chromosomes so now there are 2 nuclei

Question 16

Where does cytokinesis come in the process of mitosis?

Answer 16

• Begins at anaphase and ends at telophase.

- Its a separate process to mitosis

Question 17

Describe cytokinesis

Answer 17

• The cytoplasm divides.
• In animal cells, a cleavage furrow forms to divide the cell membrane.
• There are now 2 daughter cells that are geneticaaly identical to each other and the orginal cell.

Question 18

How can mitosis be observed?

Answer 18

-By staining chromosomes and watching them under a microscope

Question 19

Describe what you stainn to observe mitosis?

Answer 19

-Stain plant root cells

Question 20

What does meiosis produce?

Answer 20

-Gametes for sexual reproduction

Question 21

What is the role of gametes?

Answer 21

-In sexual reproduction, 2 join at fertilisation to form a zygote. the zygote then divids and develops into a new organism.