Transcript Meiosis & Mitosis

MEIOSIS & MITOSIS
Noadswood Science, 2012
Thursday, July 16, 2015
MEIOSIS & MITOSIS
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To understand meiosis & mitosis
SIZE
NUCLEUS
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The genetic information passed from parent to offspring is
contained in genes, carried by chromosomes in the nucleus
All body cells have a nucleus which contains all genetic
information
nucleus
CHROMOSOMES & GENES
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A gene is a section of DNA that carries the code for a
particular protein (made from joined amino acids)
Different genes control the development of different
characteristics of an organism – many genes are needed to
carry all the genetic information for a whole organism
Chromosomes, found in the cell nucleus, contain many
genes
DNA
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Chromosomes and their genes are made of a molecule
called DNA
DNA molecules carry the code that controls what your cells
are made of and what they do
Each chromosome is a
very long molecule of
tightly coiled DNA
MITOSIS
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Mitosis is the type of cell division that leads to growth or
repair
When a cell divides by mitosis:  Two new cells form
 Each cell is identical to the other one, and the cell they
were formed from
MITOSIS STAGES
1.
Parent cell
2.
Chromosomes make identical copies
of themselves
3.
They line up along the centre
4.
They split
5.
They move apart
6.
Two daughter cells form with
identical chromosomes to the parent
cell
MEIOSIS
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Gametes are formed from cells in the reproductive organs
by a type of cell division called meiosis
Male
Female
Reproductive Organs
Testes
Ovaries
Gametes
Sperm
Egg
MEIOSIS
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The cells that are formed by meiosis have half as many
chromosomes as the cell that formed them
Human body cells contain 23 pairs of chromosomes, while
human gametes contain 23 single chromosomes
The main features of meiosis are:  The chromosomes are copied
 The cell divides twice, forming four gametes
MEIOSIS STAGES
GENDER
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Human body cells have 23 pairs of chromosomes in the
nucleus – one of these pairs controls the inheritance of
gender (whether offspring are male or female)
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In males, the two sex chromosomes are different – XY
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In females, the two sex chromosomes are the same – XX
Male – XY
Female – XX
GAMETES & FERTILISATION
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Gametes are sex cells – the male gametes are the sperm,
and the female gametes are the eggs
Gametes contain one set of genetic information, while body
cells contain two sets of genetic information
Fertilisation is the joining or fusion of a male gamete and a
female gamete – the new cell that is formed divides over
and over again by mitosis creating the many cells that
eventually form a new individual
OBSERVATIONS
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Using the microscopes look at some cells which are
currently undergoing mitosis / meiosis…