B2 - Cell Division and Stem Cells Flashcards
Order from smallest to largest:
genes, nucleus, DNA, cell, chromosomes
genes, DNA, chromosomes, nucleus, cell
What is the sequence of bases in DNA called?
Genetic code
What are the 4 letters in genetic code?
A,T,C,G
What binds with ‘A’
‘T’
What binds with ‘C’
‘G’
What binds with ‘G’
‘C’
What binds with ‘T’
‘A’
What is DNA?
DNA is a long molecule with a double helix structure.
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
What is a gene?
A gene is a section of DNA that codes for a particular characteristic.
Characteristics are usually proteins.
So a gene is a section of DNA that codes for a protein.
genes are always in pairs TRUE OR FLASE
They are not allways, sex cells do not because they are haploid (half the number of cells). But most cells come in pairs because one comes from your mother and one comes from your father
What is the cell cycle?
The cell cycle are a series of events that take place when a cell is dividing
What are the two sections that the cell cycle is divided into?
Interphase and Mitosis
What covers most of the cell cycle?
Interphase
What happens during interphase?
DNA replication
Chromosome duplication
Organelle replication
What happens during mitosis?
Chromosomes line up at the equator of the cell
Chromosomes get pulled apart by elastic spindle fibers that attach to the chromosomes
Chromosomes gather at the two poles of the cell
The cytoplasm pinches inwards and divides (cytokinesis)
Two daughter cells produced that are diploid (2n) and genetically identical to parent cell
When and where does mitosis occur?
When:
During normal cell growth and repair in all tissues eg
when you skin your knee, cells divide to replace old, dead, or damaged cells.
Where:
In all tissues and organs except the ovaries and testes
What is the significance of mitosis?
The daughter cells produced are genetically identical to the parent cells. This allows to preserve favourable characteristics as the daughter cells produced are clones of the parent cell. However if the mother cell is susceptible to a disease it means that all the daughter cells will be too.
This can be exploited commercially during cloning. For example, a cow that produces a large yield of milk can be cloned to increase profits in agriculture.
What can go wrong with mitosis?
- MUTATIONS
The DNA may not get copied correctly leading to faulty cells that are not functional - CANCERS
Sometimes mitosis occurs too rapidly, which is uncontrolled cell division that leads to tumours (clusters of cells). Malignant tumours grow, invading surrounding tissues and organs which allows the cancer to spread.
What is a stem cell?
A stem cell is an undifferentiated cell, that can become differentiated
What are the 2 types of stem cells?
Embryonic stem cells (found in embryos) and Adult stem cells (found in bone marrow).
What do scientists use stem cells for?
To grow new cells, tissues or organs to help cure disease. E.g. Diabetes
What are the advantages and disadvantages of embryonic stem cells?
Advantages:
Embryonic stem cells can differentiate into ANY type of specialised cells
Using umbilical cord stem cells is less controversial (as it does not destroy a potential life)
Disadvantages:
Each embryo is a potential life so it is unethical to use the embryo
Some believe that no consent was given so it is unethical
There is the risk of rejection of the transplanted stem cells
There are many childless couples who would benefit more by using these embryos (to have a baby)
What are the advantages and disadvantages of adult stem cells?
Advantages:
Adult stem cells are in the bone marrow so they are accessible
It does not involve killing a potential life so no ethical issues
There is no risk of rejection if the patient’s own adult stem cells are used
Disadvantages:
The adult stem cells may contain viruses so immunosuppressant drugs may be needed
Scientists have not been successful so far in manipulating adult stem cells to produce ALL types of cells
It’s a very painful procedure as there is no anasthetic
Where can you find adult stem cells?
Flat bones, sternum, upper hip bone, ribs
Why are many people against the use of embryonic stem cells?
Killing embryos is killing a potential life
Name a disease that could be cured using stem cells?
Parkinson’s, Diabetes, Paralysis
How does differentiation take place?
The daughter cells formed, have certain genes that they can “switch on” which causes the cell to change shape and function
What are the changes that take place during differentiation?
Change in the number of organelles within a cell
E.g. muscle cells will have many mitochondria; RBCs lose their nucleus
The shape of the cell changes
e.g. the normal spherical animal cell gets pulled out into a long nerve cell or specialised to have a head, neck and tail like a sperm cell
The cell might gain special adaptations
E.g. cells lining the trachea have cilia that waft mucus and cells lining the small intestine have microvilli to increase surface area
What is the difference between mitosis and cloning?
There is no difference, mitosis is when 2 genetically identical daughter cells are produced from one mother cell. Cloning is when a genetically identical copy is made from a parent plant and animal. They are the same mechanism.
What is a haploid cell?
A haploid cell has HALF the number of chromosomes that the parent cell has.
The only haploid cells are the gametes these are sex cells
A human sperm cell would have 23 chromosomes
What is a diploid cell?
A diploid cell has the FULL NUMBER of chromosomes. This is the chromosome number of the species.
E.g. Human cells have 46 chromosomes (23 pairs)
In mitosis the daughter cells produced are diploid and genetically identical to the parent cell
What is cloning in plants?
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically
The cells are grown in a sterile, nutrient medium to produce clones
Fill in the gaps:
Plants can reproduce ASEXUALLY. The offspring are genetically _______ to the parent plant and are called _________.
A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a ____ atmosphere until the ____ develop.
Plants can reproduce ASEXUALLY. The offspring are genetically identicall to the parent plant and are called clones.
A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a _damp_atmosphere until the _roots_develop.
How do plants reproduce?
Asexually
What are the advantages of cloning?
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.
Cloning is faster than normal reproduction
What are the disadvantages of cloning?
Since the plants are genetically identical, a disease that affects one can affect all
It reduces genetic variation
Fill in the gaps: Plants can be cloned…………………………………. by using cells from the apical ……meristem………………………….. as these cells are undifferentiated cells called …stem……………………….. Cells
The main advantage of using stem cells is that you can preserve …desirable……………………… characteristics.
This form of growing plants is …faster…………………………… and …………………economical…………
Plants can be …cloned…by using cells from the apical …meristem… as these cells are undifferentiated cells called …stem…Cells
The main advantage of using stem cells is that you can preserve …desirable…characteristics.
This form of growing plants is …faster…and …economical…
