Copy into Notes…
Aim # 4: How and why does meiosis
happen?
Meiosis: sexual reproduction process
that produces sex cells, each with
half the parent’s DNA
NameDateClassScience- Ms. Sowin
Class Work # 4
Directions: For each question, type your answers in the spaces provided.
Use your notes, the websites, and the table to help you:
Go to http://www.cellsalive.com/meiosis.htm
1.Write down 3 observations the meiosis interactive (3 things you see going
on during meiosis)
a. I saw cells dividing
b. I saw one cell becoming 4 eggs
c. I saw the chromosomes line up and
break.
# of cell divisions
# of cells produced
# of chromosomes in
each new cell
Types of cells
produced
Functions in body
Mitosis in Humans
1
2
46
Meiosis in Humans
2
4
23
All body cells except
sperm and egg cells
Growth, repair,
maintenance
Sperm and egg cells
only
reproduction
2. How many cell divisions take place in meiosis?
2 cell divisons take place in meiosis
3. What kind of cells does meiosis produce and for what function?
Meiosis produces sperm and egg cells for
the function of making babies
4. How are mitosis and meiosis similar and different?
Mitosis and meiosis are similar because
they are both cells dividing. They are
different because mitosis makes body cells
and meiosis make sex cells
Most of your growth occurs because your body added new cells. New
cells are produced as old cells go through mitosis. Just before mitosis
begins, the chromosomes double. Then, the chromosomes line up and
eventually pull apart so the cell divides into 2 identical cells with the same
exact DNA. In humans, body cells originally contain 46 chromosomes and
after mitosis is complete, each new human body cell contains 46
chromosomes. Likewise, fruit flies each have eight chromosomes in their
body cells and after mitosis is complete, each new fruit fly body cell has 8
chromosomes.
Sexual reproduction involves another type of cell division called
meiosis. Like mitosis, a cell splits in half to produce two daughter cells.
Unlike mitosis, in meiosis each daughter cell divides again. As a result, a cell
that undergoes meiosis can produce 4 sex cells, each with only half as many
chromosomes as a normal body cell. Sperm and egg cells are produced by
meiosis. When a sperm and egg join, they are able to produce a zygote that
has a full set of chromosomes- half from each parent. For example, a body
male’s body cell that originally has 46 chromosomes undergoes meiosis and
produces a sperm cell that has 23 chromosomes (half of 46). A woman’s
body cell after meiosis would produce an egg cell that has 23 chromosomes.
When a man and woman reproduce together, their baby would have body
cells that have 46 chromosomes (23 + 23). Similarly, fruit fly cells that
originally have 8 chromosomes would only have half as many- 4 chromosomes
after meiosis, but a fertilized fruit fly egg would have 8 chromosomes again.
5. A cell with 100 chromosomes undergoes mitosis. How many chromosomes
are in the new body cell after mitosis is over?
(a) 200
(b) 100
© 50
(d) 0
My answer to # 5 is letter (B)
6. Which step must occur before mitosis can begin?
(a) the cell’s DNA is copied
(b) The nuclear membrane breaks down
© the chromosomes separate
(d) the cell splits in half
My answer to # 6 is letter (A)
7. A cell with 40 chromosomes undergoes meiosis to produce an egg cell.
How many chromosomes are in the egg cell?
(a) 80
(b) 60
© 40
(d) 20
My answer to # 7 is letter (D)
8. Which cells are produced by meiosis?
(a) nerve cells
(b) sperm cells
© skin cells
(d) muscle cells
My answer to # 8 is letter (B)
9. All cells in the human body have 46 chromosomes, except sperm and egg
cells. Explain why…
Sperm and egg cells are made by meiosis so
the cell divides two times to make 23
chromosomes. This is because when the
sperm and egg come back together by sex
it would make cells that have 46
chromosomes again. In other word words,
sperm and egg cells have half as many
chromosomes so when they
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