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GCSE Biology
Growth and development
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Slide 2

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What is this unit all about?
All life starts with a single cell and through the magic of
science grows and develops into a living plant or animal.
This unit is all about the growth, the specializing, the
structure and the dividing of cells.
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Slide 3

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What do the following words mean?
Zygote ­ a fertilized egg
Foetus - an unborn baby in the later stages of
development (shows some recognizable features of the
mature animal)
Embryonic stem cells ­ unspecialized cells in an embryo
that will develop into specialized cells (animal)
Meristem cells ­ unspecialized cells that can grow and
form any cells needed (plants)
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Slide 4

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Why can newts grow back limbs and humans
Newts have unspecialized cells that Humans cannot grow limbs back
when a limb is cut off, they can grow because almost all of our cells are
back what has been lost because the specialized. That means that if we loose
cells are unspecialized, they can a limb we cannot grow one back
specialize themselves to the cells that because the information that it took to
have been lost so that the limb can be grow them in the first place has been
grown back. lost. Katie…read more

Slide 5

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How are the following words related to each
DNA These words are all related to each
Chromosomes other because they are all key factors in
making proteins. The DNA is inside the
Genes genes, which make up chromosomes
Nucleus inside the nucleus. The nucleus is
Organelles protected by the nuclear membrane
and the rest of the cell is made up of
Cytoplasm cytoplasm which is a jelly-like
Cell substance which protects the nucleus
Nuclear and the nucleus is an organelle.
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Slide 6

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Explain what happens before cell division can happen...
Describe the difference between mitosis and meiosis
In both mitosis and meiosis, the cell that is being divided has to copy everything inside of it. That
means that there is then a second exact copy of every chromosome, every gene, every little
piece of DNA. However, this is where the two become different. In mitosis, all of the
chromosomes find their exact copy and are joined to each other by their centromeres to form a
cross shape
(the term for one-half of a replicated chromosome (one arm of the cross) is a
`chromatid'). The chromosomes then line up one above the other inside of the
cell. Spindle fibres then attach themselves to the centromeres and when
pressure is applied the chromosome splits forming sister chromatids, dragging
them to polar ends of the cell. This is then when the cell splits and forms two
`daughter cells'. This is what happens in mitosis, however, in meiosis, instead of
creating an exact replica of the mother cell, the aim is to simply spilt the
mother cell to end up with four daughter each with only 23 chromosomes (rather than 46).
The point of this is to create gametes (the sex cells) and that is why only half of the genetic
information is needed. To achieve this, as I said before the cell must grow and copy all of the
information inside of it. The chromatids then create cross shapes with their replica and the
chromosomes, line up in pairs next to each other (one chromosome from mum and one from
dad). The cell then divides straight down the centre of the cell so that one cell has one copy of
each chromosome and each of these new cells still has 46 chromosomes. Next, the second
division happens pretty much the same as mitosis. These chromosomes then line up one above
the other and the spindle fibres pull them to opposite ends of the cell and then it divides again,
taking half of the genetic information each. Which then leaves us with four daughter cells each PTO
with 23 chromosomes.
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