MEIOSIS:
THE FORMATION
OF THE SEX
CELLS
1.How many chromosomes
are in a human somate cell?
46
2. How are the chromosomes
arranged in a human body cell?
IN GROUPS OF TWO
3. How many chromosome
pairs are found in a body cell?
23
4. Why are the body cells said
to be diploid?
Di = two.
The chromosomes in a body
Cell are arranged in groups
Of two
5. What symbol is used to
indicate the diploid
chromosome count?
2n
6. Draw a picture showing the
23 pairs of chromosomes in a
human cell. Color the first one
pink and second one blue.
See pops note
Pops Note!
Why pink and blue?
Pink represents the
chromosome you inherited
from your mother and the blue
represents the chromosome you
inherited from your father.
7. Name the two members of
each chromosome pair:
Homologues
8. Compare and contrast the
DNA carried on each
homologue:
Compare:
Each homologue carries
information about the same
trait.
Contrast:
The information may be
different.
This loci on
both
homologues
codes for
eye color.
Each may
be coding
for different
colors.
How will the person look?
Why?
Brown is dominant over blue. He
may pass brown OR blue to his
children because he is carrying the
blue recessive gene.
9. How do the homologues
work together
The combination of the two
sets of instructions
determines the trait. The
stronger will overshadow the
weaker.
10. Where do the
homologues in each
chromosome pair come
from?
One
came
from
the
mother.
One
came
from
the
father.
11.What are gametes?
The human sex cells
12.Name of male sex cell?
SPERM
13. Name of the Female sex
cell?
Ovum
Or
Commonly
called: egg
14. What is Fertilization?
The joining of sperm and egg.
15. What is a zygote?
The fertilized egg that will
begin to multiply by mitosis
and develop into a baby.
16. Draw the fertilization
process: Color sperm blue,
egg pink, and zygote blue and
pink mixed.
egg
sperm
fertilization
zygote
17. How are the
chromosomes found in
gametes?
As individual homologues
with no matching partner.
18. How many chromosomes
are found in a human
gamete?
23
19. What is a haploid cell?
A cell that has ½ the total
chromosome count because
the homologues have been
separated by meiosis.
20. What symbol is used to
represent the haploid count?
1n
21. What is Sexual
Reproduction?
Any type of reproduction that
requires the joining of the
sperm and egg.
May be internal (mammals)
Or external (fish, frogs)
22. Why is a special type of
cell division necessary for the
creation of gametes?
The sperm and egg must
contain ½ of the genetic
information necessary to code
for each and every trait.
Pop’s Note!
Observe what happens to
the single homologues
during fertilization:
A 2n homologue pair is
formed.
23. Name the process that is
used to produce gametes:
Meiosis
24. Describe the events that
occur in meiosis: See
attached handouts.
http://www.stolaf.edu/people
/giannini/flashanimat/celldiv
ision/meiosis.swf
Prophase I
1. Single
chromosomes
have copied.
2. Two
homologous
chromosomes
team up to
form tetrads.
3. Non-sister
chromosomes
wrap around
each other and
swap gene
segments in a
process called
crossing over.
Metaphase I
1. Centrioles
move to Poles.
2. Tetrads line
up in the
middle
3. Spindle
fibers attach to
each pair of
sister
chromatids
within the
tetrad.
Anaphase I
Tetrad partners
are pulled
apart.
Sister
chromatids DO
NOT separate!
Telophase I
1. Cells divide with sister
chromatids still attached.
2. The two daughter cells are
still diploid.
Prophase II
1.Nuclear
membrane gone
2. Centrioles move
into position.
Metaphase II
Sister
chromatids line
up in the
middle.
Anaphase II
Spindle fibers
come down
and pull the
sister
chromatids
apart.
Telophase II
Two diploid
cells divide
into four
haploid
daughters.
These four
haploid cells
are ready to be
used in
fertilization.
25. What is a TETRAD?
Cluster of 2 sets of
homologous chromosomes.
26. Describe Crossing Over:
Non-sister chromatids lap over
Homologues break
One homologue section
Joins the other homologue
26. What is a chiasma?
The breaking point in the
chromosome.
27. What is the difference in
meiosis in females and
meiosis in males?
Males
Each parent cell creates four
healthy haploid sperm cells.
Females
Polar body in the ovary
produces 1 healthy egg, and 3
tiny eggs that die during
meiosis.
Only one daughter egg will
live.
28. Why is sexual
reproduction so successful?
1) Crossing over causes
variation in offspring.
2) Enrichment of gene pool
29. What do we call the regrouping that occurs during
crossing over?
GENETIC
RECOMBINATION