Transcript Document

Reproduction
Essential Question:
How do organisms reproduce more organisms like
themselves? (or, Where do babies come from?)
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All organisms are made out of cells that have
DNA and come from other cells
DNA holds the specific instructions to build
proteins which are essential for cell structure
and function
The types of proteins produced by cells
determine the structure and function of the
organism
You are a human because the instructions in
your DNA allowed your cells to build the proteins
necessary for the growth and development of a
human organism
What is
reproduction?
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Reproduction is
basically the
creation of a new
organism by the
passing of DNA
from a parent
organism to its
offspring
All living things
reproduce
How is DNA passed from parents to
offspring?
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Asexual Reproduction is when the DNA
comes from one parent. All bacteria reproduce
this way (binary fission)
Sexual Reproduction is when the DNA comes
from 2 parents - almost all animals and plants
reproduce this way
Sexual Reproduction involves the creation of
special cells, called sex cells, in order to pass the
DNA to the offspring
Where do sex cells come from?
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All cells come from other cells
Eukaryotic cells that go through the process of mitosis
make EXACT copies of themselves (one skin cell divides
to form two identical skin cells, etc.)
Sex cells (sperm and egg cells) are different from all
other cells in the body because they have half as many
chromosomes
Human body cells have 46 chromosomes, but sex cells
have only 23
So if a normal human body cell with 46 chromosomes
goes through mitosis, it will produce two body cells just
like it that have 46 chromosomes
Since your original cell had 46, all the body cells that
have been produced since have 46 chromosomes
Where do sex cells with half that number (23) come
from?
NOTES - Meiosis & Gamete
Formation
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Each organism has
many different types
of chromosomes. All
body cells in sexually
reproducing organisms
have two of each type
of chromosome, one
of each type from
each parent.
Homologous
chromosomes
How are sex cells created from body cells?
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In order to reproduce, cells must be created that
have only one of each type of chromosome
Mitosis cannot do this because mitosis creates
exact copies of the original cell
Diploid Cell – a body cell with a full
set of chromosomes (two of each type)
Haploid Cell – a sex cell with a half
set of chromosomes (one of each type)
2n → n
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If a body cell of a sexually reproducing
organism has 20 chromosomes, then the sex
cell will have 10 chromosomes
A human body cell has 46 chromosomes, so
a human sex cell has 23 chromosomes
Gamete – a haploid sex cell
(sperm in males, egg in females)
Gamete = Sex Cell = Haploid Cell = Sperm or Egg Cell
Meiosis – a type of cell division
that produces haploid gametes
Human Sex
Determination
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What does Calvin’s
mother mean when
she says “It’s your
fault we didn’t have a
sweet little girl! Your
stupid chromosome!!
Not mine!!