B2 Cell Division Flashcards
Chromosomes
Made of DNA molecules
Carries genes
The 46 chromosomes found in the human body are typically found as 23 pairs in the nucleus of body cells
Genes
A section of DNA on a chromosome that codes for a particular sequence of amino acids, to make a specific protein
The cell cycle
The series of events involved in cell growth and cell division
Allows for the growth, repair and asexual reproduction of cells
It involves:
Interphase
Mitosis
Cytokinesis
Interphase
Extra ribosomes, mitochondria and other subcellular structures are produced
The cell’s chromosomes are replicated so that there are two sets of the cell’s chromosome.
Mitosis
The duplication and distribution of chromosomes
Includes: Prophase Metaphase Anaphase Telophase
Prophase
Chromosomes thicken and coil into chromatids, duplicate chromosomes
Disappearance of the nucleolus
Disintegration of the nuclear membrane
Organisation of fibres to form a spindle
Metaphase
Chromosomes line up along the midline of the cell
Anaphase
Chromatid pairs separate
Chromatids are pulled to opposite sides of the cell by spindle fibres
Formula for length of cell cycle phase
(observed number of cells at that stage / total number of cells observed) * total length of time of a cell cycle
Karyotype
A photo of an individual’s collection of chromosomes
Asexual reproduction
Cellular reproduction that does not include the fusion of gametes or change in the number of chromosomes
Produces two identical cells
Cytokinesis
The division of the cytoplasm and cell membrane of a parent cell to two daughter cells
Growth
A permanent increase in size as a result of cell division or cell enlargement
Stem cells
Cells with the ability to develop into a range of specialised cells
Animal stem cells
Specialise in very early life
Mostly specialised by birth
Specialised cells
Cells with features to specifically make them suited to complete a certain function
Cannot duplicate by mitosis and have to be replaced by stem cells
Plant stem cells
Can differentiate throughout their lives
Undifferentiated cells are made at active regions of roots and stems called meristems
In meristems, mitosis takes place almost continuously
The plant cells do not differentiate until they have reached their final destination in the plant
Differentiation is not permanent- cells can redifferentiate
Plant cloning
Identical plants can be made from a sample of leaf tissue quickly and economically
Under the right conditions, plant cells undifferentiate and undergo mitosis
These cells can differentiate to form the tissues needed to create a new plant
Embryonic stem cells
Egg and sperm cells fuse to form a zygote
This grows into a ball of cells called an embryo
The inner cells of this ball are embryonic stem cells
They can differentiate into all of the specialised cells in the body
Adult stem cells
Stem cells in the body when it is fully grown
An undifferentiated cell of an organism that can give rise to many more cells of the same type
Other types of cells can also arise from stem cells through differentiation
Using stem cells
Embryonic stem cells can be encouraged to grow into almost any different type of cell needed in the body
What conditions can be helped with stem cells
Paralysis
Diabetes
Vision impairment
Heart conditions
Plant cloning for research
Plant cloning can produce large numbers of identical plants
This is important for research as scientists can change variables and observe the effect on genetically identical individuals
Plant cloning for agriculture
Plant cloning can produce large numbers of identical plants with special features eg disease resistance
Therapeutic cloning
The nucleus of a cell is inserted into a donor egg cell forming a blastocyst
Stem cells from the blastocyst can be removed and cultures
These cells are identical to the patient’s, reducing the risk of transplanting as the immune stem accepts them
Animal cloning through embryo transplant
An animal is artificially inseminated with sperm from a high yield male
The embryo is then removed from the uterus
Embryos can be split before they become specialised, this causes several identical embryos
These can be transplanted to host mothers
Animal cloning through adult cell cloning
The nucleus is removed from an unfertilised egg cell
The nucleus from an adult body cell is inserted into the egg cell
An electric shock stimulates the egg cell to divide to form an embryo
These embryo cells contain the same genetic information as the adult cell
When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development
Medical problems with stem cell use
Can cause cancer if their growth is not controlled (especially in people with immunodeficiencies)
Can transfer viruses
Is considered a waste of money
Ethical problems with stem cell use
The embryos can not consent its use (human rights violation)
Human reproduction should not be interfered with (religious views)
