Biology: Mitosis

Long lengths of DNA can make up sections called genes. Lots of genes make up a chromosome. We have 23 pairs of chromosomes in each cell, making 46 - 23 from each parent.

Everyone's DNA is unique, except for identical twins and clones.

DNA fingerprinting involves cutting up a strand of someone's DNA into small sections and then separating them on a piece of card. This is used in forensic science (eg to discover whose hair was left at the crime scene) and in paternity testing.

Cover the answers below and see if you have learnt the front of the card:

1) Put these in order of size: gene, chromosome, DNA
2) Two people naturally have identical DNA. What can we say about them?
3) What does DNA fingerprinting involve?
4) What might DNA fingerprinting be used for? (name two things)
5) How many chromosomes do we have in each cell?

Answers
1) DNA, gene, chromosome
2) They are identical twins
3) Cutting up DNA into small sections and separating them on a card.
4) Forensic science, paternity testing.
5) 46 (or 23 pairs)

In a cell that isn't dividing, the DNA is spread out in long strands. The DNA is not visible with a light microscope.

When the cell has been given the instruction to divide using mitosis, the DNA becomes short and fat. They become chromosomes. Each chromosome duplicates and becomes "butterfly shaped" - two lines joined at the centre (chromatid). Each "wing" is identical to its partner.

Each chromosome lines up along the centre of the cell (centromere). Then they are pulled apart along the chromatid so that each "wing" goes to the opposite end of the cell to its partner.

Membranes form around each set of chromosomes, forming the nucleus. Lastly, the cytoplasm divides.

Cover the answers below and see if you have learnt the front of the card:

1) When the cell is not dividing, can you see the strands of DNA with a light microscope?
2) What is the name for the centre of the chromosome, where the identical pairs are held together?
3) When the chromosomes divide from their partners, where do they line up?
4) What happens first: the cytoplasm divides or the membranes form?
5) What is this process called?

Answers:
1) No
2) Chromatid
3) Centromere
4) Membranes form
5) Mitosis

Mitosis forms two cells, genetically identical, each containing a full set of chromosomes.

In the human body, this happens for growth and repair. A human embryo grows rapidly by mitosis, and in an adult this is happening constantly in the bone marrow (where blood cells are created), in the nails and hair. Mitosis grows new skin after a cut or graze.

In animals and plants that reproduce asexually, mitosis is used for reproduction. Strawberry plants use mitosis to create runners for a new plant, and onions use it to grow a new bulb.

Cover the answers below and see if you have learnt the front of the card:

1) How many cells are formed from mitosis?
2) What can we say about the cells that are created? (name two things)
3) In humans, what is mitosis used for?
4) Name one place in an adult human where mitosis is used.
5) Name one place where mitosis is used to reproduce asexually.

Answers
1) Two
2) They are genetically identical, and they contain a full set of chromosomes.
3) Growth, repair
4) Nails, hair, bone marrow, cut or graze, etc.
5) Strawberry plants, onions, etc.
Thanks for reading: I hope these were helpful! Meiosis cards coming soon :)