B2 cell division Flashcards
explain differentiation
As an organism develops, cells differentiate to form different types of cells . As a cell differentiates it acquires different sub-cellular
structures to enable it to carry out a certain function. It has become
a specialised cell.
explain what chromosomes are
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.
how many pairs of chromosomes do humans have
23
what is the cell cycle
a series of changes involving growth and division
what has to happen before cell divides
Before a cell can divide it needs to grow and increase the number
of sub-cellular structures such as ribosomes and mitochondria. The
DNA replicates to form two copies of each chromosome.
what happens in mitosis
In mitosis one set of chromosomes is pulled to each end of the cell
the nucleus divides
the cytoplasm and cell membranes divide to form two
identical cells.
why is mitosis important
mitosis creates new cells for
growth and development of multicellular organisims
repairing damaged tissues
asexual reproduction
what is a stem cell
A stem cell is an undifferentiated cell of an organism which is
capable of giving rise to many more cells of the same type, and
from which certain other cells can arise from differentiation.
explain the function of meristems in plants
Meristem tissue in plants can differentiate into any type of plant cell,
throughout the life of the plant.
explain the function of human embryos
Stem cells from human embryos can be cloned and made to
differentiate into most different types of human cells.
what is therapeutic cloning
In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
what are the risks of using stem cells
The use of stem cells has potential risks such as transfer of viral
infection, and some people have ethical or religious objections.
how can meristems in plants be used
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.
what are adult stem cells
they are found in some organs and tissues e.g bone marrow
they can only make certain types of cells and their ability to divide is limited
