2.) Topic 2 Cell Division And Stem Cells Flashcards
What are chromosomes
A chromosome is a linear DNA molecule tightly coiled around proteins. It carries genetic information in the form of genes. Genes also exist in pairs, and each gene creates a code that makes a specific protein.
Just before cell division what does the DNA do?
It coils up tightly
How many chromosomes does the human body contain?
46 in total (23 pairs)
W cells divide [3]hen do
When:
An organism grows
Organisms need to replace worn-out cells
Organisms need to repair damaged tissue
What are gametes and what are special about them
Sex cells. They contain half the number of chromosomes of a normal human cell
Where is sperm and egg produced
Sperm is produced in the testes
Egg is produced in the ovaries
What is mitosis
Mitosis is the division of a mother cell to produce two genetically identical daughter cells with a full set of chromosomes (46 chromosomes). It involves one division
Why is mitosis important (4)
It is important because it allows an organism to grow, repair damaged tissues, replace old cells and asexually reproduce
How is a zygote fomed
When a male gamete fuses with a female gamete
In which type of cell division are gametes formed?
By a type of cell division called meiosis
What is meiosis
Meiosis is a type of cell division that creates four genetically different daughter cells known as gametes. Meiosis involves two divisions and produces cells with half the number of chromosomes (23 chromosomes).
Are all gametes genetically different from each other?
Yes
Why is meiosis important
For genetic variation and ensuring that the resultant zygote has a full set of chromosomes
What causes meiosis to take place?
Sexual reproduction
Comparing mitosis and meiosis x6
How many cell divisions are there?
How many cells are produced?
How many chromosomes are present?
What is it used for?
Where in the body does it happen?
Are the cells produced different or the same?
Mitosis The cells divides ONCE 2 daughter cells produced 46 chromosomes present Produce new body cells All parts of the body in non-reproductive cells Genetically identical
Meiosis The cell divides TWICE 4 gamete cells produced 23 chromosomes present How gametes are made Happens in the testes and ovaries Genetically different
What is cancer a result of?
Uncontrolled mitosis
What type of disease is cancer
A non-communicable disease
What can uncontrolled mitosis lead to the formation of?
A primary tumour and these tumour cells can break off and and spread to other tissues forming secondary tumours
What does cell differentiation produce?
Specialised cells with specialised functions
What are stem cells?
Unspecialised cells which have the capability to develop into different types/other cells
When a cell becomes specialised, can it change into anther type of cell and give an example
No it can’t
E.g. you cannot use a muscle cell to try and grow skin cells
What do stem cells form when they divide
One of the daughter cells becomes a tissue cell
What are meristems?
The source of stem cells in plants are called meristems and they are the growing points in the tips of shoots and roots
What are embryonic stem cells?
What is their function?
Unspecialised and capable of differentiating into any cell type, enable the growth and development of tissues in embryos
What is an embryo
When a fertilised egg divides to form a ball of cells. These are called embryos
What are adult stem cells?
Can develop into a limited range of cell types, enable the replacement of dead or damaged cells
Where can adult stem cells be found?
Brain Eyes Skin Muscle Blood Heart Liver Bone marrow
What are the uses of stem cell technology
[2]
Can lead to treatment or a cure for many diseases
Can be used to replace damaged tissues e.g. trachea
What are the advantages of using stem cells
Used to treat damage or disease e.g. type 1 diabetes and heart disease
Used to treat disease that would otherwise be untreatable
Not rejected by the body
No need to find a donor
No need for tissue typing
Can be used to grow organs for transplants
What are the disadvantages of using stem cells
May become contaminated during preparation and when transplanted may transmit infections to the patient
No guarantee that the treatment will work
Transplanted stem cells can cause tumours
Long term risks are unknown
Potential side effects
Suggest why some people support embryonic stem cell research, whereas others do not [2]
Some people support it because it can be used as a cure for many diseases. However some people do not because they believe it destroying a human life by destroying an embryo
State one advantage of using stem cells over the use of embryonic stem cells [1]
Avoids ethical issues e.g. killing of unborn children
What type of cell division would happen embryonic stem cells [1]
Mitosis
What does ‘undifferentiated’ mean [1]
Unspecialised
The process by which stem cells become specialized
State an advantage and disadvantage of using adult stem cells rather than embryonic stem cells [2]
Advantage - Risk of rejection is virtually non-existent
Disadvantage - Can only differentiate into into a certain number of types of cells
If a treatment for diabetes were developed, which organ would need to be treated? [1]
Pancreas
Why is meiosis important for sexual reproduction? x2
Increases genetic variation
Ensures that the resultant zygote has a full set of chromosomes
In plants, where can stem cells be found
In meristematic tissue in the root and shoot tips
Where can embryonic stem cells be collected from? [2]
Donor stem cells removed from embryos grown in vitro
Patients own stem cells removed from the umbilical blood before birth
Describe the potential uses of stem cells in medicine (4)
Treat diseases e.g. heart disease, type 1 diabetes
Used to repair damages tissue e.g. brain damage
Used in scientific research
Growing organs for transplants
What are the ethical issues related to the use of stem cells in medicine?
[3]
Embryos used to provide stem cells are destroyed - human life destroyed
Could lead to the ‘farming’ of embryos for stem cells
May lead to the reproductive cloning of humans
What is a protein
A large molecule synthesized from amino acids monomers
