Transcript Human Genetic Disorders

Human Heredity:
Karyotypes and Pedigrees
Mrs. Kooiman
LSHS
09-10
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.