1.4

Question 1

What is cell differentiation?

Answer 1

Cellular differentiation is the process by which an unspecialised cell develops more specialised functions by expressing the genes characteristic for that type of cell

Question 2

What is a meristem?

Answer 2

Meristems are groups of cells that are unspecialised which can divide repeatedly over the lifetime of the plant

Question 3

During differentiation:

1. Many essential genes remain switched on in all cells e.g. __________________
2. Some genes are switched on in certain differentiated cells only e.g. __________________
3. Unnecessary genes are switched off to prevent the production of proteins that are not required

Answer 3

The gene coding for the cellular respiration

The gene for hemoglobin in red blood cells

Question 4

Where are apical meristems found and what do they do?

Answer 4

Found at the apex (tip) of the shoots and roots. Increase the length of the plant (primary growth)

Question 5

Where are lateral meristems and what do they do?

Answer 5

Found in the cambium of the vascular bundles. These increase the girth of the plant (secondary growth)

Question 6

What are 4 main areas within the meristem?

Answer 6

1. Zone of mitosis (cell division)
2. These cells then become elongated and vacuolated
3. They they become differentiated (specialised) to perform a particular function
4. They then form part of a permanent tissue which performs a particular role within the plant

Question 7

________ is said to be meristematic and contains ________ _______which will eventually differentiate into xylem or phloem cells

Answer 7

Cambium

Undifferentiated cells

Question 8

Plant cells are totipotent. What does this mean?

Answer 8

That any cell from the plant can differentiate into any specialised cell needed to grow a whole plant. This involves the switching on of characteristic genes using growth regulators

Question 9

Stem cells are unspecialised cells that can:

Answer 9

Reproduce themselves by repeated mitosis and cell division while remaining undifferentiated
Differentiate into specialised cells when required to do so by multicellular organism that posses them

Question 10

Embryonic stem cells

Answer 10

Taken from early embryos
Pluripotent - can differentiate into any type of specialised cell
Found in blastocyst

Question 11

Tissue (adult) stem cells

Answer 11

Found in many tissues in an adult organism e.g. Bone marrow

Unipotent - can divide and differentiate to become only one type of cell

Question 12

Give an account of the process of cellular differentiation in animals and the function of meristems in plants (4)

Answer 12

1. In tissue cells some genes are switched off and other genes are switched on
2. Producing proteins characteristic of that tissue
3. Allow tissue to carry out its function
4. Meristems contain unspecialised cells
5. Found in root and shoot tips
6. Lateral meristems in stems
7. Meristem cells divide to produce cells which can differentiate to produce mature plant tissues

Question 13

Give an account of ethical issues related to stem cell use (4)

Answer 13

1. To obtain embryonic stem cells an embryo has to be sacrificed
2. But using embryonic stem cells can potentially relieve suffering and save lives
3. Stem cells could be used to treat healthy individuals
4. Stem cells could be part of an illegal trade
5. Other ethical issue explained

Question 14

Describe the differences between and similarities of cells and tissue stem cells (6)

Answer 14

Embryonic stem cells:
1. Found in developing embryo (blastocyst)
2. Have the calcify to become all cell types
3. Can be grown relatively easily in culture
Tissue stem cells:
1. Found in boy tissues
2. Are more differentiated than embryonic stem cells
3. Can only differentiate into anatomy range of cell types
4. Are rare in mature tissues
5. Give rise to a limited range of cell types
6. Develop into cell types that are closely related to the tissue in which they are found