Download When Things Go Wrong with Cell Division

Cell Division and Reproducing
New Organisms
Science 9
• Regeneration is the ability to regrow a tissue, an organ
or a part of the body
• Humans are only capable of re-growing tissue and skin
• Animals with little cell specialization are capable of
reproducing an entire organism – this is called
fragmentation
• As cells become more specialized, the ability to grow
“replacement parts” becomes limited
Regeneration
• The nucleus of every cell in the human body
contains a complete code for all your
characteristics and all cellular functions
• Every cell contains identical DNA
• Every cell, however, uses different parts of the
DNA because they are directed by different
genes
• Specialized cells only use parts of their genetic
information
Specialization and DNA
• Skin, bone marrow and other tissues
contain stem cells
• These cells are capable of continuous
dividing and may be able to differentiate
into different specialized cells
• They may be activated by an injury or
disease
Stem Cells
• Cloning is a natural process
• Asexual reproduction is an example of
cloning
• It is the process of forming identical
offspring from a single cell or tissue
Cloning
• Cells that are capable of reproducing quickly are
given hormones to encourage even faster cell
division
• They then transferred from the area where the
hormone is and growth slows down
• Cells begin to specialize and the plant begins to
form
• Delaying specialization appears to be the key in
successful plant cloning
Cloning Plants
• The nucleus is removed from an unfertilized egg
cell
• A nucleus from an embryo (reproducing cells of
a fertilized egg from sperm) is inserted into the
egg cell
• The cell continues to divide, much like a
fertilized egg, and begins to grow into an
organism
• In order for cloning to work, dividing cells
cannot begin to specialize
Cloning Animals
• Mammalian cells have been successfully cloned
• They were only successful when the nucleus used came
from a cell that was very early in its division (8 cells)
• However, the cloning of a sheep named Dolly changed
this
• Udder cells were taken from one sheep (Finn Dorset)
• Egg was taken from another sheep (Poll Dorset) and its
nucleus was removed
• The two cells fused and began to reproduce
• Cell mass was transferred back into the uterus of another
sheep (Blackface)
• Clone is born that has the genetic markings of the Finn
Dorset
Mammals and Cloning