Wake-up
Put the PowerPoint in presentation mode.
1. If Black is dominant and white is recessive. Assuming
the rules of codominance what is the phenotype for
Bb.
2. Using the same alleles from above, what would be
the phenotype for Bb assuming incomplete
dominance.
3. Cross a gray cat with a white cat. Black is dominant
(B) and white is recessive (b). What will be the
results?
Wake-up #3
Cross a gray cat with a white cat. Black is
dominant (B) and white is recessive (b).
What will be the results?
B
b
b
b
Bb x bb
Bb
Bb
Results:
bb
50% Gray, 50%
White, and 0%
Black
bb
Cell Cycle and Meiosis: Video
Watch this video using headphones. If you don’t
have your own, borrow a pair from the back of
the room.
Meiosis
Make sure the PowerPoint is in presentation
mode.
What is a Gene?
A sequence in DNA that codes (has the directions)
for a trait.
What is a TRAIT?
A trait is a genetically determined characteristic;
Example: Brown hair, freckles, etc.
What is a Homologous Pair?
A pair of chromosomes with similar genes; one chromosome
is from your mom and the other from your dad
Structure of a Chromosome
Genes from
parents
Sister Chromatids
Homologous Chromosomes
Formula: 2n
Diploid?
n = the number of chromosomes
2 = two chromosomes; homologous pairs
are present
-Normal number of chromosomes in organisms body
cells
What is a Body Cell?
All the cells that
make up the
“body” of an
organism.
Formula: n
Haploid?
n = the number of chromosomes
-Single set of unpaired chromosomes (no
homologous pairs) found in gametes.
What is a Gamete?
Reproductive cell; Sex cell
Males have sperm and females have eggs
Location of Meiosis
Within the sexual organs; males within the
testes and females within the ovaries
Brief summary of Meiosis
Process in which gametes (sex cells) are made
Need to split apart the homologous pairs;
reduce # of chromosomes by 1/2
Meiosis Intro Video (begin-1:58)
Watch me!!! Make sure to stop at 1:58
Go grab a plastic container of markers/colored
pencils. You should have one per table. I would
like the diagram to be in color in your notes.
Warning!!
I’m giving you the SHORT version of this process.
If you recall in Mitosis there was Prophase,
Metaphase, Anaphase, and Telophase?? I’m
leaving these out.
You’re Welcome!!!
When you do the activity, these phases will be
included. Don’t get confused.
Process: Meiosis
Homologous
Pairs
Crossing
over
Total
#
of
Haploid or
occurs here
Chromosomes
Diploid?
2n
4
Crossing Over
Exchange of parts between two paired
chromosomes
·
Process:
Process: Meiosis
Homologous
Pairs
MeiosisorI
Haploid
Total # of
Diploid?
Homologous
Chromosomes
Pairs
2 are
n
separated
Meiosis I Video (1:58-3:41)
Resume video. Make sure to stop at 3:41
·
Process:
Process: Meiosis
Homologous
Pairs
Haploid
Total
# ofor
Meiosis
II
Diploid?
Chromosomes
Sister
Chromatids
2
are
n
separated
Meiosis II Video (1:37-5:05)
Resume video. Make sure to stop at 5:05
Meiosis produces four
gametes (sex cells)
with HALF the number
of chromosomes
of the original cell
If an organism
has 50
chromosomes
and it undergoes
meiosis, how
many
chromosomes
will be present in
the new cells?
If an organisms diploid number chromosome
is 40, how many chromosomes will be
present in the new cells?
Let’s Practice!!!!!!
Recall that Meiosis makes cells with HALF the
number of chromosomes
Mitosis makes cells with the SAME/IDENTICAL
number of chromosome.
If an organism
has 8
chromosomes
and it undergoes
meiosis, how
many
chromosomes
will be present in
the new cells?
If an organisms diploid number is 100 and it
undergoes mitosis, how many chromosomes
will be present in the new cells?
If an organism
has 18
chromosomes
and it undergoes
mitosis, how
many
chromosomes
will be present in
the new cells?
If an organisms diploid number chromosome
is 24, what would its haploid number be?
If an organisms
diploid number
chromosome is
134,568, how
many
chromosomes
will be present in
the new cells?
134, 568
Law of Independent Assortment
Homologous chromosomes will separate
independently of each other during meiosis
It is RANDOM!!!!
Brief Summary: Fertilization
Combination of the egg and sperm to form a zygote
Process: Fertilization
ization
Brief summary of process:
Zygote
Egg
Sperm
Total # or
of
Haploid
Chromosomes
Diploid?
Total # of
Haploid
or
Chromosomes
Diploid?
Haploid
or
Total # of
Homologous
Diploid?
Chromosomes
Pairs
n2
2
n
4
2n
Process:
Fertilization
Video
(5:05-end)
Resume video.
Watch until the end.
Benefits of Meiosis
Genetic variation; We are a mixture of our parents.
This picture is my brother and his beautiful family.
Interactive Visual of Meiosis
Click on the link above to view Meiosis with
Dragons. Just read and click through the
simulation. It might help you visualize what is
happening in Meiosis.
Meiosis Activity
Get Interactive Meiosis activity from sub.
You are going to work
through several
simulations on Meiosis.
Each activity is linked on
my Wiki page. When
complete, turn it into
the bin. If you don’t
finish, take it home for
homework.