cell division and stem cells Flashcards
what is a chromosome and what does it contain
a chromosome is a linear DNA molecule tightly coiled around proteins
it contains genes
how many chromosomes are in the human body
46 chromosomes (23 pairs)
how many chromosomes are in the human body
46 chromosomes (23 pairs)
what are sex chromosomes
what are the male and female sex chromosomes
a pair of chromosomes that determine sex
male = XY
female = XX
what is mitosis
a form of cell division that produces two ‘daughter cells’
both are genetically identical to the parent cell with the same number of chromosomes (46 chromosomes)
it involves 1 division
why is mitosis important in organisms
growth
repair of damaged cells
cell replacement
asexual reproduction
wat is meiosis
a form of cell division involved in the formation of gametes
it involves two devision, producing four gametes
chromosome number is halved (23 chromosomes)
what are gametes
sex cells (e.g sperm cells egg cells) they contain half the chromosome number
why is meiosis important for sexual reproduction
it increases genetic variation
ensures that the resultant zygote has a full set of chromosomes
compare mitosis and meiosis
MITOSIS
occurs in non reproductive cells
produces two daughter cells
daughter cells are genetically identical
daughter cells have 46 chromosomes
it occurs for the growth, repair and replacement of damaged cells
MEIOSIS
occurs only in reproductive cells
produces four daughter cells
daughter cells are genetically different
daughter cells have 23 chromosomes
occurs for the formation of gametes during sexual reproduction
how is cancer caused by uncontrolled mitiosis
the rate at which cells divide by mitosis is controlled by genes
if there is a change in one of the genes that controls cell division, a cell may start dividing uncontrollably. this can result in a mass of abnormal cells called a tumour.
if the tumour invades and destroys surrounding tissues it is called cancer
what are stem cells
stem cells are unspecialised cells that can differentiate into a range of different cell types
what is meant by differentiation
the process by which a stem cell becomes specialised (have a specific function)
some genes switch on or off determining the cell type
why is cell differentiation important
enables the formation of specialised tissues with specific functions
e.g muscle tissues
what are embryonic stem cells
stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
what is the function of embryonic stem cells
enable the growth and development of tissues in human embryos
where can embryonic stem cells be collected from
donor stem cells removed from embryos grown in vitro
patients own stem cells removed from the umbilical blood before birth
what are adult stem cells
stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells
what are adult stem cells
stem cells that can differentiate into a limited range of cell types e.g bone marrow stem cells
what is the primary function of adult stem cells
replacement of dead cells
describe the potential use of stem cells in medicine
treat disease
used to repair damaged tissue
used in scientific research
growing organs for transplants
what are the ethical issues related to the use of stem cells in medicine
the embryos used to provide stem cells are destroyed and a waste of a potential human life
could lead to the ‘farming’ of embryos for stem cells
may lead to the reproductive cloning of humans
fill in the blanks
the cells in mature _____ have generally lost the ability to _____; some cells, in both _____ and _____, do not lose this ability and these are called ____ ____
the cells in mature tissues have generally lost the ability to differentiate; some cells, in both plants and animals, do not lose this ability and these are called stem cells
What are both adult and embryonic stem cells used for
To replace damaged tissue
