GT Biology
March 8, 2011
Warm-up
What type of mutations are the following?
A
ABCDEFG
ABCDEFGXYZ
B
ABCDEFG
ABEDCFG
C
ABCDEFG
ABCBDEFG
What is a karyotype?
Objective
SWBAT explain karyotypes and how they relate
to mutations
Homework
Read pgs 228-232
Answer questions 3-6
Today
What are karyotypes?
What do they tell us?
How do they relate to genetic disorders?
•What do these have in common?
•What do you think they show?
•Are they the same for all
organisms?
What is a karyotype
Karyotyping examines the chromosomes of a person
An image of chromosomes
Images are taken during metaphase
Homologs are paired and arranged by size and
shape
How to obtain a
karyotype
There are two methods to obtain a karyotype:
A cell in mitosis is photographed
Amniocentesis: amniotic fluid and cells from
the fetus are withdrawn to be tested for a
disease
These are still in mitosis
How can karyotypes be
used?
To study chromosomes and chromosomal
abnormalities
To better explain genetic disorders
Genetic Disorders
What do you think a genetic disorder is?
Can you tell if someone has sickle cell
anemia from a karyotype?
Genetic Disorders
Definition: an illness that is caused by an
abnormality that occurs within a gene or
chromosome
Polyploidy
It is possible for some cells and organisms to have more
than one set of pair homologs
Happens during mitosis or meiosis
Results in cells that are 3n, 4n, 5n or more
This most often occurs in plants but can occur in animals
Plants and fruits grow bigger than normal
These animals are often sterile
How could this be beneficial to farmers?
Types of Genetic
Disorders
Nondisjunction: the addition or deletion of a
whole chromosome
During anaphase I chromosomes do NOT
separate
The cell with an additional chromosome is
called trisomy once fertilization occurs
The cell with a deletion of a chromosome is
called monosomy once fertilization occurs
Trisomy 21: Down’s
Syndrome
•Caused by
nondisjunction
Symptoms of Down’s
Syndrome:
•Small skull
•Abnormally round head
•Slanting eyes
•Short hands
•Small mouth and
enlarged tongue
•Low muscle tone
Another Example of
Trisomy
Trisomy: Kleinfelter’s Syndrome (a male who has
feminine features)
Symptoms of
Kleinfelter’s Syndrome
•Male infertility
•Small testicles
•Round body type
•Difficulty reading, writing
and language problems
Example of Monosomy
Monosomy: Turner’s Syndrome (a female who
has prepubescent features)
Symptoms of
Turner Syndrome
•Short stature
•Low hairline
•No menstruation
•Small finger nails
•Shield Shaped
Thorax
•Folds of skin on the
neck
Cri-du-chat Syndrome
The loss of part of chromosome 5
Symptoms: stomach, intestinal and heart
problems and mental retardation
Use of Karyotypes
After learning about these types of genetic
disorders, how do you think karyotypes could be
of used?