Meiosis is the process by which sex cells are produced. It involves the copying of chromosomes followed by two cell divisions, resulting in sex cells like sperm and eggs that have half the normal number of chromosomes. During meiosis, chromosomes are copied once and the nucleus divides twice to produce cells for sexual reproduction that combine during fertilization to form offspring with the full number of chromosomes.

1. Meiosis
Where are genes located and how do
they pass information?
Understanding reproduction is the
first step to finding answers.

2. Meiosis
 Two kinds of
reproduction: asexual
and sexual. The name
for the way cells divide
in asexual reproduction
is mitosis.
Asexual = not sexual =
example: skin cell

3. Asexual Reproduction
 In asexual
reproduction, only
one parent cell is
needed.
 This type of cell
reproduction is
known as mitosis.
Most of the cells in
your body
reproduce this way.

4. Sexual Reproduction
 In sexual
reproduction, two
parent cells join
together to form
offspring that are
different from both
parents.

5.  Parent cells are
called sex cells.
Sex cells are
different from
regular body cells
because they only
have 23
chromosomes,
which is half of our
other body cells.

6. Meiosis
 Sex cells are made
during a process
called meiosis.
 Meiosis is a copying
process that
produces cells with
half the usual
number of
chromosomes.

7. Genes and Chromosomes
Walter Sutton was a graduate student who
studied grasshopper sperm and egg cells.
 Walter Sutton’s important observation was that
egg and sperm cells were different, but they
did have something in common: Their
chromosomes were located inside a nucleus.

8.  Sutton proposed
that genes are
located on
chromosomes!

9. The Steps of Meiosis
 Chromosomes are
copies once, and
then the nucleus
divides twice. The
resulting sperm and
eggs have half the
number of
chromosomes of a
normal body cell.

10.  Sex chromosomes carry genes that
determine sex
 Female chromosomes XX
 Male chromosomes XY

11. Sex Linked Disorders
 Because males
have only one X
chromosome, what
is more likely to
happen to them?
 More likely to
have a sex-linked
disorder

12.  Name two sex-linked disorders: hemophilia, color
blindness

13. Genetic Counseling & Selective Breeding
 To trace a trait
through
generations of a
family, you can
use a pedigree

14.  A genetic
counselor can
often predict if a
person is a
carrier of
hereditary
diseases.
 People with cystic
fibrosis have two
recessive alleles.

15.  When organisms
with desirable
characteristics are
mated by humans, it
is called selective
breeding.
 Examples of
selective breeding:
race horse, show
dogs, roses