3.8.2.1 Most of a cell's DNA is not translated

Question 1

Cell differentiation

Answer 1

The process by which cells become specialised for different functions.
Specialised cells produce different proteins because different genes are expressed (switched on).

Question 2

A totipotent cell

Answer 2

A totipotent cell is a single cell that can give rise to a new organism.
It is an unspecialised that can differentiate (divide and produce) into any type of body cell.

Question 3

Meristems

Answer 3

Meristems are tissues in a plant consisting of undifferentiated totipotent cells capable of indeterminate growth.

Meristematic tissue can allow plants to regrow structures or even form entirely new plants (vegetative propagation).

Question 4

Stem cells are unspecialised cells that have two key qualities:

Answer 4

1. Self Renewal – They can continuously divide and replicate
   (risk : cancer cell)
2. Potency – They have the capacity to differentiate into specialised cell type (growth / repair)

Question 5

Types of Stem Cells
There are four main types of stem cells present at various stages of human development:

usage
stages

Answer 5

Totipotent – Can differentiate into any type of cell & form an entire organism. Present in a zygote & the early embryo (most risk)

Pluripotent – Can form most cell types. Usually derived from the inner cell mass of the blastocyst (Embryonic & fetal stem cells). They divide in unlimited numbers to treate human disorder.

Multipotent – Can differentiate into a number of closely related cell types (e.g. haemopoietic adult stem cells in bone marrow, umbilical cord blood)

Unipotent – Differentiate into a single cell type they maintain and repair adult tissues. e.g.cardiomyocytes

Question 6

aseptic technique

Answer 6

● Disinfect surface - to kill bacteria on the surface so contamination doesn’t occur
● work close to Bunsen flame - to allow for upward convection current to sterilize the air
● use a sterilised pipette OR Flame the neck of any bottles / spender/ loop - to maintain a pure culture of bacteria
● Wash hands with soap - to prevent contamination fom bacteria on hands
● open the petri dish lid as little as possible - to prevent bacteria in the dish getting out and bateria in the air getting in and contaminating the plate
● soak contaminated pipette tips in disinfectant - to kill bacteria and prevent spreading outside the lab

Question 7

process of turning specialised cell to unspecialised totipotent cell (Callus)

Answer 7

dedifferentiation

Question 8

Induced pluripotent stem cells (iPS cells)
- what is it
- which cell to which cell
- how (name)
- pros

Answer 8

Unipotent stem cells can be made to go ‘back in time’ and become pluripotent again.
Body (somatic) cells can be genetically altered to make them acquire the characteristics of embryonic stem cells.
Genes that have been turned off are turned on again by nuclear reprogramming.
This overcomes many of the ethical issues associated with using embryonic stem cells.