B2 Cell Division Flashcards
How many chromosomes do human body cells have
46
How many chromosomes do gametes cells have
23
Chromosomes
Coiled up lengths of DNA molecules
Why are chromosomes normally found in pairs
Body cells have 2 copies of each chromosome one from organism’s mother and one from it’s father
What do chromosomes contain
Large number of genes which control development of different characteristics
Why do cells divide
To produce new cells
Mitosis
The stage of the cell cycle when the cell divides
What do multicellular organisms use mitosis for
To grow or replace cells that have been damaged
3 steps of cell cycle
Growth
DNA replication
Mitosis
What happens during growth and DNA replication
Cell grows and increases amount of subcellular structures such as mitochondria and ribosomes
It then duplicates DNA so there’s 1 copy for each new cell
DNA copied and forms X-shaped chromosome
What happens during mitosis
Chromosome lines up at centre of cell
Cell fibres pull them apart
Chromosomes go opposite ends of cell
Nuceleus divides
Cytoplasm and cell membrane divode
Now have 2 new daughter cells with exact same DNA
Why genetic material must be doubled during mitosis
It’s important that the daughter cells have a copy of every chromosome
Describe a situation where mitosis is occurring
Replacing skin cells
Gene
A section of DNA which controls part of a cell
Gamete
A reproductive cell of an animal or plant
Why mitosis is important for living organisms
Mitosis helps organisms grow in size and repair damages tissue
Differentiation
Process when a cell changes to become specialised for its job
What happens as cells change
They develop different subcellular structures and turn into different types of cells
This allows them to carry out specific functions
When does differentiation occur
As organism develops
In most animal cells when do animals lose their abilities to differentiate
Lost at an early stage
What are differentiated cells in mature animals mainly used for
Repairing
Replacing cells
Growth
An increase in total mass of a cell
Examples of specialised cells
Sperm cells, nerve cells, phloem and xylem cells
Function and adaptation of sperm cells
To get male DNA to the femal DNA
Long tail and streamlined head
Function and adaptation of nerve cells
Carry electrical signals
Are long and roundhead
Function and adaptation of muscle cells
To contract quickly
Contain lots of mitochondria, multiple nuclei
Function and adaptation of root hair cells
Absorbs water from the soil by osmosis
Large surface area increases rate of absorption, storage roots
Function and adaptation of phloem cells
Moves food in plants
Have few subcellular structures, sieve tubes
Function and adaptation of xylem cells
Transports water in plants
Hollow tube, strengthened by lignin
Compare and contrast differentiation in plants and animals
Animals can differentiate in early stages of life
Plants can differentiate throughout their whole life
Why plant clones are genetically identical to each other
Clones contain identical sets of genetic material in the nucleus
How using tissue culture creates a clone of a plant
Sample of tissue is extracted then separated
Cells are cultured and grown with help of growth medium
These cells replicate and can be divided again
Explain why it is easier to clone a plant compared to an animal
Plants are totipotent, meaning they can differentiate into any type of cell
Animal cells have more limited ability to differentiate
How to clone a plant using apparatus correctly
A branch from the parent plant is cut off
Its lower leaves are removed
Stem is planted in damp compost
Stem cell
A cell that is not differentiated
Embryonic stem cell
A type of stem cell derived from early-stage embryo
Adult stem cell
Type of stem cell found in various tissues of the body after development
Differences between embryonic and adult stem cells
Embryonic cells found from embryos, adult cells found in various tissues
Embryonic cell can differentiate into any type of cell and adult cells can’t
Advantages of adult stem cells
Less likely to cause immune rejection in treatments
They don’t involve destruction of embryos
Disadvantages of adult stem cells
Harder to grow in laboratory
Only differentiate to limited number of cells
Advantages of embryonic stem cells
Can differentiate into any type of cell
Can treat wide range of diseases
Disadvantages of embryonic stem cells
Ethical concerns
Risk of immune rejection
Ethical concerns of embryonic stem cells
People believe destroying an embryo is equivalent to taking a human life
People believe life starts at birth and an embryo is a life and so should be treated with as much respect as a fully developed human
Embryo has potential to be human killing it
Why embryonic stem cells are useful for treating medical conditions
They are very useful for treating diseases because of their ability to become any cell type and their potential to regenerate damaged tissues
Why adult stem cells are useful for treating medical conditions
They are useful as they can differentiate into specific cell types related to the tissue or organ where they’re found which is helpful for repairing and regenerating tissues
Why are plant clones are produced in the agriculture industry
It allows a variety of a plant with desirable characteristics to be produced cheaply, quickly and on a large scale
Ways that stem cells can be used to help medical conditions
Replace cells damaged by chemotherapy or disease
Serves as a way for the donor’s immune system to fight some types of cancer and blood-related diseases
Use of stem cells
To treat conditions when bone marrow is damaged and no longer able to produce healthy blood cells
How do prokaryotic cells replicate
Binary fission
Therapuetic cloning
Steps 1-4
Human egg taken from donor
Remove egg nucleus
Insert patients DNA
Stimulate cell division
Therapuetic cloning
Steps 5-7
Develop blastocyst
Extract stem cells
Differentiate cells
What therapeutic cloning can be used for
Studying diseases
Diabetes treatment
Organ repair
