Meiosis Notes
How are living things different?
Living organisms that undergo sexual reproduction must have 2 parents. Sexual reproduction
produces variation (differences) in organisms of the same species.
These organisms have offspring that are similar but not identical to the parent. The DNA of
each parent comes together to make different combinations of traits for offspring. These
different combinations are possible due to meiosis.
Meiosis basics
-There are two types of cells:
Body cells
&
(full set of chromosomes)
Sex cells
(half the amount of chromosomes)
-Meiosis is a type of cell division only for sex cells.
-The end result of meiosis is 4 cells with half the amount of chromosomes as the original cell
Diagram of Meiosis
Original number of chromosomes
for the organism
Chromosomes replicate then divide
into 2 daughter cells
No replication. Cells divide
into 4 daughter cells with half
the original number of
chromosomes
How does meiosis produce so much variation?
Meiosis has two rounds of cell division. During cell
division there is a process known as crossing-over,
which helps swap genetic information from the
chromosomes. This allows for different combinations
of DNA information in each sperm or egg cell.
Practice Problems:
______ 1) An alligator has a total of 36 chromosomes in its body cells. How many chromosomes
would be in its sex cell?
a) 36
c) 10
b) 18
d) 72
______ 2) A cat has a total of 22 chromosomes. After undergoing meiosis, how many
chromosomes would be present in an sperm cell?
a) 2
c) 11
b) 22
d) 44
______ 3) If an organism has 20 chromosomes in its sex cells. How many chromosomes would
be present in a skin cell?
a) 10
c) 30
b) 20
d) 40