3.7- MITOSIS

Question 1

How can cell division happen? (2)

Answer 1

by either mitosis or meiosis

Question 2

What does mitosis produce?

Answer 2

two daughter cells that have same number of chromosomes as parent cell + each other

Question 3

What does meiosis produce?

Answer 3

four daughter cells, each with half the number of chromosomes of parent cell

Question 4

What is mitosis?

Answer 4

division of cell that results in each of the daughter cells having an exact copy of DNA of parent cell

Question 5

In what cases do the daughter cells of mitosis not have the exact copy of DNA of the parent cell?

Answer 5

mutation

Question 6

When does mitosis precede?

Answer 6

period during which cell not dividing

Question 7

What is the period when a cell is not dividing called?

Answer 7

interphase

Question 8

What is the period of interphase of?

Answer 8

period of considerable cellular activity that includes a very important event, replication of DNA

Question 9

Where is the two copies of DNA after replication remain joined at?

Answer 9

centromere

Question 10

What four stages can mitosis be divided into?

Answer 10

prophase
metaphase
anaphase
telophase + cytokinesis

Question 11

What firstly happens in prophase?

Answer 11

chromosomes first become visible

Question 12

How do the chromosomes change in prophase?

Answer 12

become visible, initially as long thin threads, which later shorten + thicken

Question 13

What do animal cells contain for mitosis?

Answer 13

two cylindrical organelles called centrioles

Question 14

Where do the centrioles move to during prophase?

Answer 14

move to opposite ends (called poles) of cell

Question 15

What do the centrioles develop in prophase?

Answer 15

spindle fibres which span cell from pole to pole

Question 16

What are spindle fibres collectively called?

Answer 16

spindle apparatus

Question 17

What shows that centrioles are not essential for spindle fibre formation?

Answer 17

as plant cells lack centrioles but do develop spindle apparatus

Question 18

What happens to the nucleolus + nuclear envelope in prophase?

Answer 18

nucleolus disappears

nuclear envelope beaks down, leaving chromosomes free in cytoplasm of cell

Question 19

Where are the chromosomes drawn towards in prophase?

Answer 19

towards equator by spindle fibres attached to centromere

Question 20

What happens to the chromosomes by metaphase?

Answer 20

chromosomes seen to be made up of two chromatids

Question 21

What is each chromatid? (metaphase)

Answer 21

identical copy of DNA from parent cell

Question 22

What are the chromatids joined by? (metaphase)

Answer 22

centromere

Question 23

What is attached to the centromere? (metaphase)

Answer 23

some microtubules from the poles

Question 24

What happens when some microtubules from the poles are attached to the centromere? (metaphase)

Answer 24

chromosomes pulled along spindle apparatus + arrange themselves across equator of cell

Question 25

What happens in anaphase?

Answer 25

centromere divides into two + spindle fibres pull individual chromatids making up chromosome apart

Question 26

Where and how do the chromatids move after the centromere divides into two? (anaphase)

Answer 26

chromatids move rapidly to respective, opposite poles of cells

Question 27

When the chromatids move to the opposite poles of the cell what are they referred to as? (anaphase)

Answer 27

chromosomes

Question 28

Where is the energy of the chromatids moving to the opposite poles of the cell come from?

Answer 28

provided by mitochondria

Question 29

What do the mitochondria do in anaphase?

Answer 29

gather around the spindle fibres

Question 30

What happens if the cell is treated with chemicals that destroy the spindle? (anaphase)

Answer 30

chromosomes remain at equator, unable to reach the poles

Question 31

What happens in telophase?

Answer 31

chromosomes reach their respective poles + become longer + thinner, finally disappearing altogether, leaving only widely spread chromatin

Question 32

What happens to the spindle fibres in telophase?

Answer 32

spindle fibres disintegrate

Question 33

What happens to the nuclear envelope + nucleolus in telophase?

Answer 33

re-form

Question 34

What happens after telophase?

Answer 34

cytoplasm divides

Question 35

What is the process of the cytoplasm dividing called?

Answer 35

cytokinesis

Question 36

What is the process of cell division in prokaryotic cells called?

Answer 36

binary fission

Question 37

What is step 1 of binary fission?

Answer 37

circular DNA molecules replicate + both copies attach to cell membrane

Question 38

What is step 2 of binary fission?

Answer 38

plasmids also replicate

Question 39

What is step 3 of binary fission?

Answer 39

cell membrane begins to grow between two DNA molecules + begins to pinch inward, dividing cytoplasm into two

Question 40

What is step 4 of binary fission?

Answer 40

new cell wall forms between two molecules of DNA, dividing original cell into two identical daughter cells, each with single copy of singular DNA + variable number of copies of plasmids

Question 41

Why can't viruses undergo cell division?

Answer 41

they're non-living

Question 42

How do viruses replicate?

Answer 42

by attaching to their host cell with attachment proteins on their surface

Question 43

What do viruses do after attaching to the host cell with their attachment proteins in replication?

Answer 43

inject their nucleic acid into host cell

Question 44

What does the genetic information of the injected viral nucleic acid from the virus provide in replication?

Answer 44

"instructions" for host cell's metabolic processes to start producing viral components, nucleic acid, enzymes + structural proteins, which are then assembled into new viruses