key area 4: cellular differentiation

Question 1

explain what cellular differentiation means

Answer 1

differentiation is a process by which unspecialised cells become Altered and adapted to form a specialfunction in the body of a living organism.

Question 2

define meristems

Answer 2

growth is restricted to regions called meristems. These are Groups of unspecialised plant cells capable of dividing throughout the life of the plant

Question 3

Define stem cells

Answer 3

Unspecialised cells that can’t reproduce themselves by repeated mitosis and cell division. They differentiate into specialised cells when required to do so

Question 4

Give 2 examples of specialised plant cells and describe the types of genes that are expressed in each

Answer 4

1) root hair cell has large surface are to absorb water and minerals
2) leaf cell has lots of chloroplasts to absorb sunlight for photosynthesis

Question 5

Describe the process of differentiation into specialised cells from embryonic and tissue in animals

Answer 5

In the embryonic cells all the genes are switched on or have the potential to be switched on. As development proceeds the cells undergo differentiation and becomes specialised. Once a cell has become specialised it only expresses the genes that code for proteins specific to the role of the cell
Tissue stem cells have a narrower differentiation potential as many of their genes are already switched off

Question 6

Describe 3 examples of present or future therapeutic uses of stem cells

Answer 6

Can repair damaged or diseased organs and tissues
rebuilding bones And cartilage
Repairing damaged immune systems

Question 7

Describe 3 other areas in which stem cell research can be useful

Answer 7

Used as models to study how diseases develop
For drug testing
Research for causes of genetic defects in cells

Question 8

Describe the main ethical issues relating to the different types of stem cell use

Answer 8

Many people believe an early embryo is classified as a human and therefore the removal of stem cells which destroys an embryonic is equivalent to ending a human life. Others believe that carrying out research using stem cells is helping to treat nasty diseases such as cancer

Question 9

Selective gene expression

Answer 9

Genes can be switched on or off when they are required otherwise the body would waste energy producing proteins in cells where they are not needed.

Question 10

Embryonic stem cells

Answer 10

Come from very early embryos (5-14 days after fertilisation) called blastocysts. Embryonic stem cells have the potential to differentiate into any type of cell found in the body (multi potent)

Question 11

Apical meristems

Answer 11

Found at the top of the root and the shoot which adds length to the plant.

Question 12

Lateral meristems

Answer 12

Allow the stem to thicken. It is called cambium and produces new vascular bundles (xylem and phloem) to transport food and water in the stem of perennial plants. Each year it produces an animal ring of xylem. The number of rings indicates the age of the plant