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Bellwork: Identify which “PHASE” the cells are going
through and DRAW that cell.
Standard: (B.6G) recognize the
significance of meiosis in sexual
reproduction
Essential Question: What is
meiosis and how is it different than
mitosis?
Chromosomes
Chromosomes are coiled
DNA located in the cell
nucleus.
An organism inherits one
chromosome from each
parent.
How many parents do you
have?
So you have ____ sets of
each chromosome.
2 copies of each
chromosome =
homologous
chromosomes
A cell that contains 2 sets of homologous
chromosomes is said to be diploid.
2N = diploid cell.
Because N = number of chromosomes
Sexual Reproduction & Our Cells
On a cellular level, what happens
during sex?
Biologically speaking, what’s the
point of sex?
Sexual reproduction
combines DNA from 2
parents.
Gametes are sex cells, also
known as the sperm and the
egg.
When each parent forms
gametes (egg, sperm) in their
body, they can only have 1
set of chromosomes instead
of 2.
During fertilization,
1 + 1 = 2 sets of
chromosomes.
When gametes (sex cells)
are formed, there must
be a process that
separates the two sets
of genes so that each
gamete ends up with
just one set.
Because gametes contain only 1 set of chromosomes
they are said to be haploid.
N = haploid
N= number of sets of chromosomes in the cell
Meiosis
Meiosis is a process in
which the number of
chromosomes per cell is
cut in half through the
separation of
homologous
chromosomes in a
diploid cell.
** Meiosis is how
gametes are produced**
Meiosis usually involves two divisions.
By the end of meiosis, the 1 diploid cell that
entered meiosis has become four haploid cells.
Results of Meiosis
In male animals, the haploid gametes produced by
meiosis are called sperm.
In female animals, the haploid gametes produced by
meiosis are called eggs.
Mitosis vs. Meiosis
Mitosis results in two genetically identical diploid cells.
Mitosis is used for growth.
Meiosis results in four genetically different haploid cells.
Meiosis is used for gamete production and increased genetic variation.
Debrief…answer the question for your
color
• One: What is the purpose of mitosis and
meiosis?
• Two: What are the steps/stages of mitosis?
• Three: What is cancer and how is it caused?
• Four: Describe how DNA changes during the cell
cycle.