Meiosis Vocabulary
Functions and Pictures…
What is DNA?
• DeoxyriboNucleic Acid
– the genetic
material that
carries
information
about an
organism and is
passed from
parent to
offspring
What are Chromosomes?
• Rod-shaped cellular structures
made of condensed chromatin;
contain DNA that carries the
genetic information which
controls inherited
characteristics such as eye
color and blood type
• A chromosome pair looks like
an X
• You have 23 PAIRS(2ndiploid) in every cell
– (one from dad / one from
mom)
• Except for sperm or egg cells
which have only 23 (no pairs)
What is Asexual Reproduction?
• The reproductive
process that
involves only one
parent and
produces
offspring that are
identical to the
parent
What is Sexual Reproduction?
• The reproductive
process that
involves two parents
who combine their
genetic material to
produce a new
organism, which
differs from both
parent
What is Meiosis?
• Produces
gametes- sex
cells (sperm
and egg) by
which the
number of
chromosomes is
reduced by half
What are Homologous
chromosomes?
• Chromosomes
from the female
and male that
contain the
same genes
(ex. #1 from
male and #1
from female)
Random Chromosome
Segregation
• Are all the four haploid cells that result
from meiosis the exact same? Why or why
not?
• What causes this randomness?
• Random segregation of homologous
chromosomes and sister chromatid
• Crossing over
Independent Assortment
What are Gametes?
• A sperm cell
or an egg
cell, haploid = n
What is Fertilization?
• The joining
of a sperm
cell and an
egg cell
First…the sperm has to get there!
What is a Zygote?
• A fertilized egg,
produced by the
joining of a
sperm and an
egg
• This is right
after fertilization
happening
Mitosis vs. Meiosis
What happens in Reproduction?
DNA is passed from parent to offspring in two possible ways…
Sexual Reproduction
• 2 parents
• Produces a
combination of
chromosomes that is
different from the
parent
• Creates genetic
diversity
Asexual Reproduction
• 1 parent
• Offspring have same
chromosomes and is
identical to the parent
What are the benefits?
Sexual Reproduction
Asexual Reproduction
• Creates Genetic
Diversity
• It is Fast…
– Children are different
from the parents
– If one dies from a
disease, others MAY
be able to survive it
– Can produce lots of
offspring (kids) really
fast! (20 minutes)
• Only need one
“parent”
What are the drawbacks?
Sexual Reproduction
Asexual Reproduction
• You need two
“parents”
• Can be slow
• The offspring (kids)
are the same as the
“parents”
– Elephants are
pregnant for 2 years!
– If one can die from a
disease, then all can
die from the same
disease…
– All may have illness
What happens in
Sexual Reproduction?
Produces gametes (sex cells)
•Female (eggs)
•Large cells
•Don’t move
•Male (sperm)
•Smaller cells
•Flagella: used to move
cell toward egg cell
Fertilization (joining of egg & sperm)
Zygote (fertilized egg)
New living organism with genetic variation
Advantage: creates offspring with genetic diversity
How many chromosomes does a
human cell have?
•46 or
23
pairs
What happens in meiosis?
• Meiosis is the process
when chromosome pairs
separate to form four new
sex cells with half the
number of chromosomes
Parent cell
(copies DNA)
46
Mitosis
(cell divides)
92
Meiosis:
cells divide
again
23
46
46
23
23
23
(sperm or egg cells)
What happens when sex cells combine?
• When sex cells
(gametes) combine to
produce offspring,
each sex cell will
contribute to the
offspring half (23) the
normal number of
chromosomes (46)
sperm
egg
23
23
46
Closure Questions
1.
2.
3.
4.
5.
6.
7.
Explain the difference between asexual and sexual
reproduction.
What is the advantage of sexual reproduction?
What are the two types of gametes made in sexual
reproduction?
How many chromosomes do human cells have?
At the end of meiosis how many cells are made?
At the end of meiosis, the new cells have how many
chromosomes compared to the original parent cell?
When sex cells combine to produce offspring, each sex
cell will contribute how many number of
chromosomes?