Download Mitosis Meiosis

Genetics is a study of heredity
How traits are passed from one
generation to the next.
DNA is the material that holds the
information about your traits
• Chromosomes are long pieces of DNA.
• Segments of DNA along the chromosomes
hold instructions for different traits
How are traits passed to offspring?
Two types of reproduction:
Asexual and Sexual
Asexual reproduction
• Prokaryotes
• Requires only ONE parent
• Offspring inherit DNA from just one parent
and are therefore identical to parent.
• Process is called BINARY FISSION and happens
just like mitosis to form TWO identical
offspring.
Sexual Reproduction
• Eukaryotes: plants, animals, fungi and protists
• TWO parents
• Offspring get a complete set of chromosomes
from BOTH parents for a total of TWO copies
of every gene in all body cells.
• Requires specialized SEX CELLS called gametes
(egg and sperm cells)
Sexual Reproduction
• Offspring have some traits like the mother and
some like the father.
• How are SEX CELLS made???
Meiosis makes sex cells
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Makes egg and sperm cells
Like mitosis
DNA gets copied before it starts
Different because the nucleus divides TWO
TIMES to make four cells
• Each sex cell has just ONE copy each
chromosome, where body cells have TWO
copies
REMEMBER:
• Gametes (egg and sperm cells) have HALF as
much DNA (one set) as body cells (two sets).
Fertilization: no peeking…
You are kidding,
right???
This works PERFECTLY
• Egg and sperm each give ONE copy of DNA to
the baby so that it has TWO copies, one from
each parent.
• This is how you get traits from both your mom
and your dad
Humans
• We inherit one set of 23 chromosomes from
each parent for a total of 46 chromosomes.
• Scientists number them from 1-23
• Each matching pair of chromosomes (ex:
chromosomes #1 inherited from mom and #1
inherited from dad are called HOMOLOGOUS
CHROMOSOMES.
Mitosis
To make BODY cells
Purpose
Meiosis
To make SEX cells for
reproduction
To grow
To repair injuries
Sex cells = gametes
= eggs and sperm
cells
Mitosis
Which cells do it
Happens in all BODY cells
Meiosis
Happens in SEX organs of
eukaryotes
Mitosis
# Daughter Cells
TWO daughter cells
Meiosis
FOUR daughter cells
Mitosis
How much DNA
In Eukaryotes, SAME
amount of DNA as
parent cell.
Daughter cells identical to
parent cell
Meiosis
In Eukaryotes, HALF as
much DNA as parent
cell.
Daughter cells are ready
to combine with
another sex cell to
reproduce.
Mitosis
In Humans:
TWO sets of 23
chromosome:
One set inherited from
mom and one set
inherited from dad
Meiosis
ONE set of 23
chromosomes:
MIXED from parent’s DNA
Mitosis
Remember
Meiosis
My-TOE- sis
Mini-Meiosis
Mitosis makes body cells
for growth and repair
Meiosis makes SEX cells to
make a mini me.