B2 - Cell Division and Stem Cells

Question 1

Order from smallest to largest:
genes, nucleus, DNA, cell, chromosomes

Answer 1

genes, DNA, chromosomes, nucleus, cell

Question 2

What is the sequence of bases in DNA called?

Answer 2

Genetic code

Question 3

What are the 4 letters in genetic code?

Answer 3

A,T,C,G

Question 4

What binds with ‘A’

Answer 4

‘T’

Question 5

What binds with ‘C’

Answer 5

‘G’

Question 6

What binds with ‘G’

Answer 6

‘C’

Question 7

What binds with ‘T’

Answer 7

‘A’

Question 8

What is DNA?

Answer 8

DNA is a long molecule with a double helix structure.
The nucleus of a cell contains chromosomes made of DNA molecules.
Each chromosome carries a large number of genes.
In body cells the chromosomes are normally found in pairs

Question 9

What is a gene?

Answer 9

A gene is a section of DNA that codes for a particular characteristic.
Characteristics are usually proteins.
So a gene is a section of DNA that codes for a protein.

Question 10

genes are always in pairs TRUE OR FLASE

Answer 10

They are not allways, sex cells do not because they are haploid (half the number of cells). But most cells come in pairs because one comes from your mother and one comes from your father

Question 11

What is the cell cycle?

Answer 11

The cell cycle are a series of events that take place when a cell is dividing

Question 12

What are the two sections that the cell cycle is divided into?

Answer 12

Interphase and Mitosis

Question 13

What covers most of the cell cycle?

Answer 13

Interphase

Question 14

What happens during interphase?

Answer 14

DNA replication
Chromosome duplication
Organelle replication

Question 15

What happens during mitosis?

Answer 15

Chromosomes line up at the equator of the cell
Chromosomes get pulled apart by elastic spindle fibers that attach to the chromosomes
Chromosomes gather at the two poles of the cell
The cytoplasm pinches inwards and divides (cytokinesis)
Two daughter cells produced that are diploid (2n) and genetically identical to parent cell

Question 16

When and where does mitosis occur?

Answer 16

When:
During normal cell growth and repair in all tissues eg
when you skin your knee, cells divide to replace old, dead, or damaged cells.

Where:
In all tissues and organs except the ovaries and testes

Question 17

What is the significance of mitosis?

Answer 17

The daughter cells produced are genetically identical to the parent cells. This allows to preserve favourable characteristics as the daughter cells produced are clones of the parent cell. However if the mother cell is susceptible to a disease it means that all the daughter cells will be too.

This can be exploited commercially during cloning. For example, a cow that produces a large yield of milk can be cloned to increase profits in agriculture.

Question 18

What can go wrong with mitosis?

Answer 18

1. MUTATIONS
   The DNA may not get copied correctly leading to faulty cells that are not functional
2. CANCERS
   Sometimes mitosis occurs too rapidly, which is uncontrolled cell division that leads to tumours (clusters of cells). Malignant tumours grow, invading surrounding tissues and organs which allows the cancer to spread.

Question 19

What is a stem cell?

Answer 19

A stem cell is an undifferentiated cell, that can become differentiated

Question 20

What are the 2 types of stem cells?

Answer 20

Embryonic stem cells (found in embryos) and Adult stem cells (found in bone marrow).

Question 21

What do scientists use stem cells for?

Answer 21

To grow new cells, tissues or organs to help cure disease. E.g. Diabetes

Question 22

What are the advantages and disadvantages of embryonic stem cells?

Answer 22

Advantages:
Embryonic stem cells can differentiate into ANY type of specialised cells
Using umbilical cord stem cells is less controversial (as it does not destroy a potential life)
Disadvantages:
Each embryo is a potential life so it is unethical to use the embryo
Some believe that no consent was given so it is unethical
There is the risk of rejection of the transplanted stem cells
There are many childless couples who would benefit more by using these embryos (to have a baby)

Question 23

What are the advantages and disadvantages of adult stem cells?

Answer 23

Advantages:
Adult stem cells are in the bone marrow so they are accessible
It does not involve killing a potential life so no ethical issues
There is no risk of rejection if the patient’s own adult stem cells are used
Disadvantages:
The adult stem cells may contain viruses so immunosuppressant drugs may be needed
Scientists have not been successful so far in manipulating adult stem cells to produce ALL types of cells
It’s a very painful procedure as there is no anasthetic

Question 24

Where can you find adult stem cells?

Answer 24

Flat bones, sternum, upper hip bone, ribs

Question 25

Why are many people against the use of embryonic stem cells?

Answer 25

Killing embryos is killing a potential life

Question 26

Name a disease that could be cured using stem cells?

Answer 26

Parkinson’s, Diabetes, Paralysis

Question 27

How does differentiation take place?

Answer 27

The daughter cells formed, have certain genes that they can “switch on” which causes the cell to change shape and function

Question 28

What are the changes that take place during differentiation?

Answer 28

Change in the number of organelles within a cell E.g. muscle cells will have many mitochondria; RBCs lose their nucleus The shape of the cell changes e.g. the normal spherical animal cell gets pulled out into a long nerve cell or specialised to have a head, neck and tail like a sperm cell The cell might gain special adaptations E.g. cells lining the trachea have cilia that waft mucus and cells lining the small intestine have microvilli to increase surface area

Question 29

What is the difference between mitosis and cloning?

Answer 29

There is no difference, mitosis is when 2 genetically identical daughter cells are produced from one mother cell. Cloning is when a genetically identical copy is made from a parent plant and animal. They are the same mechanism.

Question 30

What is a haploid cell?

Answer 30

A haploid cell has HALF the number of chromosomes that the parent cell has. The only haploid cells are the gametes these are sex cells A human sperm cell would have 23 chromosomes

Question 31

What is a diploid cell?

Answer 31

A diploid cell has the FULL NUMBER of chromosomes. This is the chromosome number of the species. E.g. Human cells have 46 chromosomes (23 pairs) In mitosis the daughter cells produced are diploid and genetically identical to the parent cell

Question 32

What is cloning in plants?

Answer 32

Stem cells from meristems in plants can be used to produce clones of plants quickly and economically The cells are grown in a sterile, nutrient medium to produce clones

Question 33

Fill in the gaps: Plants can reproduce ASEXUALLY. The offspring are genetically _______ to the parent plant and are called _________. A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a ____ atmosphere until the ____ develop.

Answer 33

Plants can reproduce ASEXUALLY. The offspring are genetically _identicall_ to the parent plant and are called _clones_. A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a _damp_atmosphere until the _roots_develop.

Question 34

How do plants reproduce?

Answer 34

Asexually

Question 35

What are the advantages of cloning?

Answer 35

Rare species can be cloned to protect from extinction. Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers. Cloning is faster than normal reproduction

Question 36

What are the disadvantages of cloning?

Answer 36

Since the plants are genetically identical, a disease that affects one can affect all It reduces genetic variation

Question 37

Fill in the gaps: Plants can be cloned…………………………………. by using cells from the apical ……meristem………………………….. as these cells are undifferentiated cells called …stem……………………….. Cells The main advantage of using stem cells is that you can preserve …desirable……………………… characteristics. This form of growing plants is …faster…………………………… and …………………economical…………

Answer 37

Plants can be ...cloned…by using cells from the apical …meristem… as these cells are undifferentiated cells called …stem…Cells The main advantage of using stem cells is that you can preserve …desirable…characteristics. This form of growing plants is …faster…and …economical…