10 school days ‘till Winter Break!
Please do the following:
• pick up the handouts
• you have 10 minutes to finish & submit your
Oreo Mitosis video to Google Classroom
You started as a cell smaller than
a period at the end of a sentence…
amoeba
 a parent cell creates two
genetically identical
daughter cells
 Growth
 Repair
amoeba
 Somatic cells aka
regular body cells
 Skin cells
 Fingernail cells
 Bone cells
That makes somatic
cells DIPLOID (2n)
• 1 set of chromosomes
came from your
mother (n)
• 1 set of chromosomes
came from your
father (n)
• Chromosomes are
found in
homologous pairs
(two of each
chromosome – 2n)
Typical Human Family Tree
Creating Haploid Cells
12
• Meiosis is:
–Cell division that halves the # of
chromosomes
–The process that germ cells go through
to produce gametes (sperm & egg)
–Fundamental basis of sexual
reproduction
The zygote is a
unique genetic
mixture of both
parents.
• Diploid (2n)  Haploid (n)
from mom
from dad
child
too
much!
meiosis reduces
genetic content
The right
number!
• A cell containing 20 chromosomes
(diploid) at the beginning of
meiosis would, at its completion,
produce cells containing how many
chromosomes?
10 chromosomes (haploid or 1n)
16
• daughter cells contain half the
number of chromosomes as the
parent cell
• produces gametes (sperm & egg)
• occurs in the testes in male
• occurs in the ovaries in females
A pair of the same
chromosomes, one
from mom and one
from dad, get
blended together to
form a single
chromosome that is
a mixture of both
parents DNA.
• Homologous
chromosomes in a
tetrad cross over each
other
• Pieces of
chromosomes or
genes are exchanged
• Produces Genetic
recombination in the
offspring
• Yes!
• It is called nondisjunction.
– Chromosomes don’t separate properly and some gametes
end up with too many or not enough chromosomes.
makes genetically unique cells
makes genetically identical cells
allows asexual reproduction
allows sexual reproduction
occurs in somatic cells
occurs in germ cells
new cells have full set of chromosomes
(diploid)
new cells have half set of chromosomes
(haploid)
number of divisions – 1
number of divisions – 2
makes 4 daughter cells
makes 2 daughter cells