B2 - Cell Division Flashcards
What part of the cell contains chromosomes?
The nucleus
What do chromosomes carry?
The genes
What are genes
Sections of the DNA which contain the instructions for making new cells
How many chromosomes do humans have?
46 chromosomes
How many chromosomes does a haploid cell have?
23 chromosomes
How many chromosomes does a diploid cell have?
46 chromosomes
What are gametes, and give two examples.
Sex cells - egg cells and sperm cells
What is the name of the series of stages cells undergo to divide?
The Cell Cycle
What process is involved in the cell cycle?
Mitosis
What is the product of mitosis?
Two identical cells
What is asexual reproduction?
Reproduction with a single parent
Why is there no genetic variation in asexual reproduction?
Genes of the cell is taken from a single parent therefore there will be no variation.
At what time in your life is the cell cycle the shortest?
When a baby is developing in the womb.
At what point is the cell cycle the longest?
Old age
When does the cell cycle in a person begin to slow down?
After puberty
What cells continue to divide (fairly) rapidly throughout your life?
Cells in the hair, the skin, the blood, and the lining of the digestive system
Which stage is the longest stage in the cell cycle?
The first stage
What happens in stage 1 of the cell cycle?
Cells grow bigger
Mass increases
Continue with normal cell activities
Replicates their DNA
Forms two copies of each chromosome
Ready for division
Increase the number of sub-cellular structures:
• Mitochondria
• Ribosomes
• Chloroplasts (plants)
What happens in stage 2 of the cell cycle?
Mitosis
One set of chromosomes is pulled to each end of the dividing cell
Nucleus divides
What happens in stage 3 of the cell cycle?
Cytoplasm and cell membranes divide to form two identical daughter cells
About how many body cells die every minute?
300 million
What is a stem cell?
An undifferentiated cell
What happens to a cell to become differentiated?
Some of the genes are switched off, except those that will be used for its specific function
What are two places stem cells can be taken from in humans?
Embryo
Adult bone marrow
Where are stem cells found in plants?
Tips of the roots and shoots - meristems
Why aren’t nerve cells replaced when they are damaged?
They do not divide
They are not replaced by stem cells
In a mature animal, what is cell division mostly for?
Repair and replacement of damaged cells
How many times can a plant cell differentiate?
As many as they want
How often does mitosis take place in the meristems?
Almost continuously
How do plant cells grow?
They elongate
Producing identical offspring is known as what?
Cloning
How does cloning a plant work?
Under the right conditions, a plant cell will become unspecialised.
These cells then undergo mitosis
More undifferentiated cells are therefore made
Under new conditions, the now-stem cell will differentiate into a different cell
Necessary plant tissues such as:
Xylem, phloem, photosynthetic cells, and root hair cells
can be made.
The new plant will be identical to the original
Why is it difficult to clone animals?
Most stem cells differentiate early i embryo development.
They cannot be reverted.
Egg and sperm cells fuse to form a?
Zygote
The zygote divides and becomes what?
A hollow ball of cells called an embryo
What are found in the inner cells of the embryo
Embryonic stem cells
What do embryonic stem cells do?
Differentiate to form all the specialised cells in the body
Why can spinal injuries cause paralysis?
Spinal nerves cannot repair themselves
What breakthrough occurred in 1998?
Two scientists managed to culture human embryonic stem cells, capable of forming other cells
What happened in 2010?
The first trials testing the safety of injecting nerve cells into the spinal cords of paralysed human patients were carried out.
What happened in 2014?
Doctors transplanted embryonic stem cells into the eyes of people going blind as a result of macular degeneration
It was a small study to check the safety of the technique.
What happened as a result of the test in 2014?
The patients found that they could see better
How can cloning be used to save rare plants from extinction?
They can produce a large number of one plant very quickly, economically, safely and reliably.
Where may embryonic stem cells come from?
Aborted embryos
Spare embryos from fertility treatments
What ethical issues surround the use of embryonic stem cells?
The embryo cannot give permission - this is a violation of human rights
What is a religious reason against using embryonic stem cells?
Some religions cannot accept any interference with the process of human reproduction
Describe the progress of developing the use of embryonic stem cells
Slow, expensive, difficult, hard to control
What is a health issue with adult stem cells?
They may be infected with viruses - they can therefore be transferred between people
What is another issue with the use of adult stem cells?
They may trigger an immune response.
How must patients combat immune responses?
Immunosuppressant drugs which stop their body from rejecting new cells
What are two other places that scientists have recently discovered to host embryonic stem cells?
Umbilical cord
Amniotic fluid
What is therapeutic cloning?
Using cells from an adult to produce a cloned early embryo of themselves.
What would therapeutic cloning provide?
A source of perfectly matched embryonic stem cells.
What medical treatments could therapeutic cloning be used for?
Growing new organs for the original donor
Why would the new organs not be rejected by the body?
They have been made by the body’s own cells and have the same genes
Where have scientists discovered stem cells in adults?
The tubes that connect the liver and the pancreas to the small intestine
What have these stem cells been successfully turned into?
Special insulin-producing cells
In the UK, stem cell research is being carried out into potential therapies to treat what?
Spinal cord after injuries Diabetes Heart after damage Eyesight Damaged bone and cartliage
