Cell division

Question 1

Where do chromosomes carry genetic information?

Answer 1

-in a molecule called DNA

Question 2

Mitosis ensures that when a cell divides…

Answer 2

…each new cell produced has the same genetic information.

Question 3

Where is the DNA?

Answer 3

-in a cell’s nucleus within structures called chromosomes

Question 4

What is DNA?

Answer 4

-genetic material found in chromosomes inside the nucleus of a cell

Question 5

What is a chromosome made of?

Answer 5

• a single molecule of DNA

Question 6

When a cell divides, the DNA copies itself and then…

Answer 6

…coils and condenses to form the chromosomes we see in micrographs.

Question 7

How many chromosomes does the nucleus of a human body cell contain?

Answer 7

-46

Question 8

How can the 46 chromosomes in a human body cell be arranged?

Answer 8

-in 23 pairs

Question 9

The 23rd pair of chromosomes in a human body cell are…

Answer 9

…the sex chromosomes, determines the sex of the human,

Question 10

If the human is female, its 23rd chromosome will be…

Answer 10

XX (two x chromosomes)

Question 11

If the human is male, its 23rd chromosome will be…

Answer 11

XY (one x and one y chromosome)

Question 12

When does a cell divide?

Answer 12

-when an organism grows
-when an organism becomes damaged and needs to produce new cells

Question 13

6 main stages of the cell cycle

Answer 13

-DNA is uncoiled and invisible, replicates itself

-DNA coils up into visible chromosomes
>line up across the middle of the cell, attached to spindle fibres

-chromatids (copies) separate from eachother and move to opp. ends of the cell

-chromosomes reach the end of the cell and begin to uncoil

-cytokinesis: cytoplasm divides into 2, 2 genetically identical daughter cells formed, where set of chromosomes in each new cell are identical

Question 14

How do you find out the length of time of a stage in a cell cycle in minutes ?

Answer 14

observed number of cells at that stage/ total number of cells observed x 60

Question 15

What is a stem cell?

Answer 15

-unspecialised cell
>can differentiate into other cell types

Question 16

An embryo develops from a fertilised egg. Cells at the early stages in the development of the embryo…

Answer 16

…are stem cells.

Question 17

If cells are removed from the embryo – called embryonic stem cells - they will…

Answer 17

…differentiate into any cell type.

Question 18

What are adult stem cells?

Answer 18

-stem cells found in limited numbers at certain locations in the adult body

Question 19

Bone marrow adult stem cells can only differentiate into blood cells and cells of the immune system but not other cell types.
What does this show?

Answer 19

-that adult stem cells can differentiate into related cell types only

Question 20

Where does cell division in plants occur?

Answer 20

-meristems

Question 21

What can cells of the meristem do?

Answer 21

-differentiate to produce all types of plant cells at any time during the life of the plant

Question 22

Where are the main meristems of a plant found?

Answer 22

-at the tip of the root and tip of the shoot

Question 23

In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip…

Answer 23

…they become differentiated – they enlarge and develop vacuoles.

Question 24

True or False
stem cells of meristems can be used to make clones of plants quickly and cheaply

Answer 24

T
- can help endangered species close to extinction
-make plants resistant to diseases/pests

Question 25

How do animals and plants produced by sexual reproduction begin life?

Answer 25

-as a single cell -a fertilised egg/zygote

Question 26

What must a single cell do?

Answer 26

-divide to form a multicellular organism -differentiate so cells develop features to fulfil specific roles

Question 27

How does the use of stem cells of meristems to clone plants help endangered species from extinction?

Answer 27

-much quicker than allowing plants to reproduce and collecting and sowing seeds > an efficient way of producing new individuals from endangered plants >preserves the species

Question 28

How can we use human stem cells to treat diseases?

Answer 28

-to replace cells that have been damaged or destroyed e.g. >type 1 diabetes >in cases of spinal cord or brain injury

Question 29

What human stem cells do you use?

Answer 29

-embryonic stem cells -adult stem cells

Question 30

Why are embryonic stem cells better than adult stem cells?

Answer 30

-they can differentiate into a wider range of cell types

Question 31

What are chromosomes made up of?

Answer 31

-DNA molecules combined with proteins >contain genes which provide the instructions for protein synthesis

Question 32

What is a gene?

Answer 32

-section of DNA which codes for a protein

Question 33

How many chromosomes found in the nucleus of gametes (sperm and egg)?

Answer 33

23

Question 34

Why is mitosis important?

Answer 34

-produces identical cells which all have the same genetic information -produces additional cells for growth and repair or to replsce damaged ones

Question 35

Describe the first stage of the cell cycle

Answer 35

-longest stage: -cells grow, increase in mass -replicate DNA -synthesise more organelles

Question 36

Describe the second stage of the cell cycle

Answer 36

-each chromosome in a pair is pulled to opposite poles of the cell, then the nucleus divides

Question 37

Describe the third stage of the cell cycle

Answer 37

-cytoplasm and cell membrane divide- 2 identical daughter cells are produced

Question 38

What is the function of stem cells in embryos?

Answer 38

-can replicate themselves and differentiate into many other types of cells -can treat conditions such as paralysis/diabetes by dividing to replace damaged cells

Question 39

What is the function of stem cells in adult bone marrow?

Answer 39

-can differentiate into a few cell types to replace dead or damaged tissues

Question 40

What is the function of stem cells in meristems?

Answer 40

-they are undifferentiated -can divide by mitosis -to give rise to new tissues

Question 41

What is therapeutic cloning?

Answer 41

-process where an embryo is created with the same genes as a patient -to produce embryonic stem cells >won't be rejected by the patient's body

Question 42

Advantages of of cloning plants using meristem stem cells

Answer 42

-fast and effective way of producing more plants and so prevents rare plants for extinction -produce large numbers of plants with favourable characteristics -produce identical plants for research

Question 43

What are the issues of using stem cells?

Answer 43

-development of stem cell therapies are slow, expensive and hard -if donor stem cells have a different genetic makeup to patient, immune response could be triggered -adult stem cells infected with viruses could transfer infections to patients -many stem cells from aborted embryos- some have ethical/religious objection

Question 44

Cells differentiate to become..

Answer 44

..specialised

Question 45

Where did adult stem cells come from?

Answer 45

-they were leftover embryonic stem cells that didn't specialise

Question 46

Where are adult stem cells found?

Answer 46

-brain -bone marrow -blood -muscle -eyes -skin -liver -heart

Question 47

Why do gametes only have 23 chromosomes that aren't paired?

Answer 47

-they are haploid

Question 48

How is a colony of bacteria formed from a bacterium?

Answer 48

-cell division -bacterium divides into more bacteria

Question 49

Explain why sexual reproduction can produce a new variety of a plant

Answer 49

-fusion of gametes leads to a mixing of genetic information -one copy of each gene from each parent >causing variation

Question 50

During mitosis, how do the number of chromosomes in the daughter cells compare to that in the original cell?

Answer 50

-they are the same

Question 51

What is a chromatid?

Answer 51

-copy of a chromosome during cell division

Question 52

What is interphase?

Answer 52

-active life of a cell during which the cell prepares for mitosis

Question 53

A gamete is..

Answer 53

...a sex cell.

Question 54

What is haploid?

Answer 54

-describes a cell/nucleus of a gamete that has an unpaired set of chromosomes (half the normal number)

Question 55

Explain why root hair cells are considered specialised cells

Answer 55

-have a specific role in the plant (to absorb water and mineral ions)

Question 56

In 2012, Professor Shinya Yamanaka of Kyoto University won a Nobel Prize. Professor Yamanaka discovered that adult cells can be reprogrammed to become induced pluripotent stem cells (iPSCs). iPSCs are stem cells with the same properties as embryonic stem cells. Describe the possible benefits of Professor Yamanaka's discovery

Answer 56

-new cells have potential to produce any cell type -no need to use embryonic stem cells -less chance of rejection

Question 57

Give two reasons why new cells need to be produced throughout an organism's life

Answer 57

-growth and repair of tissues -replace dead or damaged tissues

Question 58

What happens to a cell before cell division happens?

Answer 58

-growth in sub-cellular structures -DNA replication

Question 59

How does a drug that separates spindle fibres from the chromosomes stop cell division?

Answer 59

-chromosomes cannot be pulled by the fibres to each end of the cell -nucleus cannot divide

Question 60

How does a drug that separates spindle fibres from the chromosomes stop the growth of a cancer?

Answer 60

-tumour cannot grow