Transcript Karyotype
Human Heredity:
Karyotypes and Pedigrees
Mrs. Kooiman
LSHS
09-10
The people in your family have
similar traits:
Who do you look like?
Your mom?
Or do you take after your dad?
Vocabulary
karyotype
sex chromosome
autosome
pedigree
Human Chromosomes
By taking a look at the nucleus, we will see
chromosomes of a human cell.
To analyze chromosomes, cell biologists
photograph cells in mitosis, when the
chromosomes are fully condensed and easy to
see.
The biologists then cut out the chromosomes
from the photographs and group them together
in pairs.
A picture of chromosomes arranged in this way
is known as a karyotype (KAR-ee-uh-typ).
Karyotype
These
human
chromosomes have
been cut out of a
photograph and
arranged to form a
karyotype.
There are 46
chromosomes in
this karyotype of
somatic cells
There are 23 pairs
of somatic cells
The first 22 pairs
are called
autosomes
The last pair are
called sex
chromosomes
XX = Female
XY = Male
What is the gender
of this karyotype?
Males and females are born in a roughly 50 : 50
ratio because of the way in which sex
chromosomes segregate during meiosis.
All
human
egg cells
carry a single
X
chromosome.
However,
half
of all sperm
cells carry an
X
chromosome
and half carry
aY
chromosome.
This ensures
that just
about half, 2
out of 4, of
the zygotes
will be XX
This
ensures
that just about
half, 2 out of 4,
of the zygotes
will be XY
Pedigree Charts
Human
genes are inherited according to
the same principles that Gregor Mendel
discovered in his work with garden peas.
However, in order to apply Mendelian
genetics to humans, biologists must
identify an inherited trait controlled by a
single gene to ensure that the trait is
actually inherited and not the result of
environmental influences.
A
pedigree
chart shows
the
relationships
within a
family
A CIRCLE
represents a
Female,
A SQUARE
represents a
Male, ■
A
HORIZONTAL
line represents
a marriage
A VERTICAL
line and a
BRACKET
connect the
parents to their
children
Generation 1
had 5 children
How many
sons?
How many
daughters?
The children
are listed from
LEFT to
RIGHT
The OLDEST
child is first
The
YOUNGEST
child is last
A SHADED circle
or square means
the person
expresses the
trait.
An OPEN circle
or square means
the person does
not express the
trait.