491572
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Mind Map by sian.allison, updated more than 1 year ago
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Created by sian.allison
over 10 years ago
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Mitosis and Meiosis
- Mitosis
- Our cells need to be able to divide
- Mitosis makes new cells for Growth and Repair
- Body cells normally have two copies of
each chromosome-one from the mother
and one from the father. So humans have
two copies of chromosomes 1 and
chromosomes 2 etc
- The 23rd pair of chromosomes are different
- When a body cell divides it
needs to make new cells
identical to the original
cells-with the same number
of chromosomes
- This is mitosis its used when
plants and animals want to grow
or replace cells that have been
damaged
- This is mitosis its used when
plants and animals want to grow
or replace cells that have been
damaged
- Mitosis is when a cell reproduces itself by splitting to form two identical offspring
- In a cell thats not dividing, the DNA is all spread out in long strings
- If the cell gets a signal to divide, it needs to duplicate its DNA - so theres 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
- The chromosomes then line up at the center of the cell and cell fibres pull them
apart. The two arms of each chromosomes go to opposite ends of the cell
- Membranes form around each of the sets of chromosomes.
These become the nuclei of the two new cells
- Lastly the cytoplasm divides
- You now have two new cells containing exactly the same DNA - they are identical
- You now have two new cells containing exactly the same DNA - they are identical
- Lastly the cytoplasm divides
- Membranes form around each of the sets of chromosomes.
These become the nuclei of the two new cells
- The chromosomes then line up at the center of the cell and cell fibres pull them
apart. The two arms of each chromosomes go to opposite ends of the cell
- If the cell gets a signal to divide, it needs to duplicate its DNA - so theres 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
- In a cell thats not dividing, the DNA is all spread out in long strings
- Body cells normally have two copies of
each chromosome-one from the mother
and one from the father. So humans have
two copies of chromosomes 1 and
chromosomes 2 etc
- Asexual Reproduction also uses Mitosis
- Some organisms also reproduce by mitosis e.g. strawberry
plants form runners in this way which become new plants
- This is an example of asexual reprodcution
- The offspring have exactly the same genes as the parent theres no variation
- The offspring have exactly the same genes as the parent theres no variation
- This is an example of asexual reprodcution
- Some organisms also reproduce by mitosis e.g. strawberry
plants form runners in this way which become new plants
- Our cells need to be able to divide
- Meiosis
- Gametes have half the usual number of chromosomes
- During sexual reproduction two cells called gametes (sex cells) combine to form a new individual
- Gametes only have one copy of each chromosome. This is so that you can combine one sex cell from
the mother and one sex cell from the father and still end up with the right number of chromosomes in the
body cells. For example human body cells have 46 chromosomes. The gametes have 23 chromosomes
each so that when an egg and sperm combine you get 46 chromosomes again
- The new individual will have a mixture of two chromosomes so it will inherit
features from both parents. This is how sexual reproduction produces
variation
- The new individual will have a mixture of two chromosomes so it will inherit
features from both parents. This is how sexual reproduction produces
variation
- Gametes only have one copy of each chromosome. This is so that you can combine one sex cell from
the mother and one sex cell from the father and still end up with the right number of chromosomes in the
body cells. For example human body cells have 46 chromosomes. The gametes have 23 chromosomes
each so that when an egg and sperm combine you get 46 chromosomes again
- During sexual reproduction two cells called gametes (sex cells) combine to form a new individual
- Meiosis involves two divisions
- To make new cells which only
have half the original number of
chromosomes cells divide by
meiosis. It only happens in the
reproductive organs e.g. orvaries
- To make new cells which only
have half the original number of
chromosomes cells divide by
meiosis. It only happens in the
reproductive organs e.g. orvaries
- Meiosis produces cells which have half the normal
number chromosomes
- As with mitosis before the cell starts to divide it duplicates
its DNA - one arm of each chromosome is an exact copy of
the other arm
- In the first division in meiosis (there are two divisions) the
chromosome pairs line up in the center of the cell
- The pairs are then pulled apart so each new cell
only has one copy of each chromosome. Some of
the fathers chromosomes and some of the
mothers chromosomes go into each new cell
- In the second division the chromosomes line up again
in the center of the cell. Its a lot like mitosis. The arms
of the chromosomes are pulled apart
- You get four gametes each with only a single set of chromosomes in it
- You get four gametes each with only a single set of chromosomes in it
- In the second division the chromosomes line up again
in the center of the cell. Its a lot like mitosis. The arms
of the chromosomes are pulled apart
- The pairs are then pulled apart so each new cell
only has one copy of each chromosome. Some of
the fathers chromosomes and some of the
mothers chromosomes go into each new cell
- In the first division in meiosis (there are two divisions) the
chromosome pairs line up in the center of the cell
- As with mitosis before the cell starts to divide it duplicates
its DNA - one arm of each chromosome is an exact copy of
the other arm
- Gametes have half the usual number of chromosomes
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