Year 10 Biology mocks

Chromosomes contain genetic information. Most cells in your body contain a nucleus - the nucleus contains your genetic material in the form of chromosomes.

Chromosomes are coiled up lengths of DNA molecules. Each chromosome carries a large number of genes. Different genes control the development of different characteristics (like hair colour).

Body cells normally have two copies of each chromosome -  one from the organism's mother and one from it's father. 

The diagram (in the AQA Biology textbook page 15) shows the 23 pairs of chromosomes from a human cell.

Body cells in multicellular organisms divide to produce new cells as part of a series of stages called the cell cycle (Page 15 in AQA Biology book). The stage where the cell divides is called mitosis. Multicellular organsims use mitosis to grow or replace cells that have been damaged. The two main stages of the cell cycle:

Growth and DNA replication - The DNA is spread out in long strings. Before it divides the cell has to grow and increase the amouth of subcellular structures like mitochondria and ribosomes. It then duplicates it's DNA - so there's one copy for each new cell. The DNA is copied and forms X-shaped chromosomes, exact duplicates.

Stem cells are undifferentiated cells and can divide to produce lots more undifferentiated cells. They can differentiate into different types of cell depending on what instructions they're given. They are found in early human embryos. Adults also have stem cells, but they're only found in places like bone marrow - they can't turn into any cell type, only certain ones like blood cells. 

They can be grown in a lab to produce clones (genetically identical cells) and made to differentiate into specialised cells to use in medicine or research. 

Adult cells can help cure - leukaemia, faulty blood cels etc

Embryonis cells can help cure - diabetes, spinal paralysis, alzheimers, parkinsons,  osteoerthritis and much more