Topic 2 - Cells And Control Flashcards
What does the nucleus contain?
It contains your genetic material in the form of chromosomes.
What are chromosomes?
They’re coiled up lengths of DNA molecules.
How many copies of each chromosome do body cells normally have?
2.
What is the name for something having two copies of chromosomes?
Diploid.
When a cell divides by mitosis, describe the cells produced.
It makes two cells identical to the original cell - the nucleus of each new cell contains the same number of chromosomes as the original cell.
Why do multicellular organisms use mitosis?
To grow or replace cells that have been damaged.
What’s asexual reproduction?
When organisms use mitosis to reproduce.
What happens in interphase?
In a cell that’s not dividing, the DNA is all spread out in long strings. Before it divides, the cell has to grow and to increase the amount of sub cellular structures such as mitochondria and ribosomes. It then duplicates its DNA so there’s one copy for each new cell. The DNA is copied and forms x-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other.
What are the four stages of mitosis is order?
Prophase, metaphase, anaphase and telophase.
What happens in prophase?
The chromosomes condense, getting shorter and fatter. The membrane around the nucleus breaks down and the chromosomes lie free in the cytoplasm.
What happens in metaphase?
The chromosomes line up in the centre of the cell.
What happens in anaphase?
Cell fibres pull the chromosomes apart. The two arms of each chromosome go to opposite ends of the cell.
What happens in telophase?
Membranes form around each of the set of chromosomes. These become the nuclei of the two new cells. The nucleus has divided.
What happens in cytokinesis?
Before telophase ends, the cytoplasm and cell membrane divide to form two separate cells.
What is produced at the end of mitosis?
The cell has produced two new daughter cells. Each daughter cell contains exactly the same set of chromosomes in its nucleus as the other daughter cell. They’re genetically identical diploid cells. They’re also genetically identical to the parent cell.
What is growth?
An increase in size and mass.
What’s cell differentiation?
The process by which a cell changes to become specialised for its job. Having specialised cells allows multicellular organisms to work more efficiently.
What’s cell division?
A cell dividing by mitosis.
What is cell elongation?
Where a plant cell expands, making the cell bigger so making the plant grow.
When you’re younger, what is most cell division for.
Growth, when you’re younger cells divide at a faster rate until you’re an adult.
When you’re fully grown, what is most cell division for?
Repair.
Where does growth usually occur in plants?
In the tips of roots and shoots.
How is the rate of cell division controlled?
By genes in an organisms DNA.
What is a tumour and how is it caused?
If there’s a change in one of the genes that controls cell division, the cell might start dividing uncontrollably. This can result in a tumour which is a mass of abnormal cells.
What is cancer?
If the tumour invades and destroys surrounding tissue its called cancer.
What are undifferentiated cells called?
Stem cells.
Where are stem cells found?
In human embryos or adult bone marrow.
What’s the difference between stem cells in the embryo and in the adult bone marrow?
Embryonic stem cells have the potential to divide and produce any type of cell at all, whereas bone marrow stem cells aren’t as versatile as embryonic stem cells as they can only produce certain cell types.
What are found in meristems?
The only cells in plants that divide by mitosis.
Where is meristem tissue found?
They’re found in the areas of plant that are growing e.g. the tips of the roots and shoots.
What do meristems produce?
Unspecialised cells that are able to divide and form any cell type in the plant.
What are the risks of stem cells in medicine?
Tumour development, disease transmission and rejection.
How can stem cells cause tumour development?
Stem cells divide very quickly - if scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop.
How can stem cells effect disease transmission?
Viruses live inside cells. If donor stem cells are infected with a virus and this isn’t picked up, the virus could be passed on to the recipient and so make them sicker.
How can stem cells effect rejection?
If the transplanted cells aren’t grown using the patients own stem cells, the patients body may recognise the cells as foreign and trigger an immune response to try and get rid of them.
What is the spinal chord?
A long column of neurones (nerve cells) that run from the base of the brain down to the spine.