Karyotypes and Mutations
Karyotype
• An orderly display of magnified
images of the individual’s
chromosomes
• Shows the
chromosomes as
they appear in
metaphase.
What is a Normal Karyotype?
• We are supposed to have 46
total chromosomes in each cell
(22 pairs of autosomes = 44,
+ 2 sex chromosomes).
Amniocentesis
• Take fluid from
amniotic fluid
around the baby
• Amniocentesis
• Blood draw
• Chorion sac
draw
Preparing a Karyotype
• 1. Use
blood cells.
Essay: Preparing a Karyotype
• 2. Burst
RBC (red
blood cells-have
no nucleus) in
hypotonic
solution.
• Release WBC
(white blood
cells).
Essay: Preparing a Karyotype
3. Use a centrifuge to
separate the white blood
cells from the rest of the
blood fluid
centrifuge
Preparing a Karyotype
• 4. Add chemical (colchicine) to stop
the chromatids in metaphase (stops
spindle fibers from forming)
• making a karyotype video
Preparing a Karyotype (cont)
• 5.
Drop on a slide.
Preparing a Karyotype (cont)
• 5. Take a picture
• 6.Sort by size and shape from largest to
smallest
Types of Karyotypes
• Fluorescent to detect a marker showing
certain defect
karyotype procedure
video 4:29
Types of Karyotypes
• Ideogram:
bands
locate sites on
chromosome
Normal Karyotype
• WHY?
• Is it a
Male or a
female?
Down Syndrome Karyotype
• Trisomy 21
• Due to
nondisjunction
(chrom did not
separate evenly)
Down Syndrome
• Trisomy 21
• Folds over eyes
• Sluggish muscles
• Mental Problems
(IQ often below 50)- but
Some much higher
Down Syndrome
• The most common
chromosome number
abnormality
• Small head, ears,
mouth
• round face, short neck
and arms
• flattened nose bridge
• small, irregular teeth
Down Syndrome
• Short Stature
• heart defects
• susceptibility to
respiratory infection ,
leukemia, ADHD,
Alzheimer’s
We Are More ALike Than Different (2:40)
Does the mother’s age matter?
• As the age of
the mother
increases
above 30, the
frequency of
Trisomy 21
also increases
Abnormal Sex Chromosomes
• 47 XXY syndrome
• Klinefelter’s
male
testes small (sterile)
breast enlargement
feminine body
contours (wider hips)
• 1 in 500 to 1,000
newborn males
•
•
•
•
Klinefelter’s Syndrome
•also
XXYY,
XXXY,
XXXXY
TURNER SYNDROME
• XO (only one X)
• Short
• often web of skin
between neck and
shoulders
• sterile
• poor breast
development
Turner Karyotype
Abnormal Chromosome Numbers
• Aneuploidy
– Missing or extra
chromosome
• Polyploidy
– Extra set of chromosomes
– Usually lethal
– Common in cancer
– Common in plants, some fish and amphibians
30
• Triploid seedless watermelon
Larger polyploid strawberry
What about…
• MUTATIONS?
Chromosomal Mutations
• most often brought on by problems that
occur during meiosis or by mutagens
(chemicals, radiation, etc.) = cancercausing agent
• Often harmful
Can you find the changes?
DELETION
Fragment of the
chromosome is
lost
Could even be
fatal
Duplication
Fragment of one
chromosome attaches
to a homologous
chromosome
Maybe no harm.
Translocation
Fragment
reattaches in
reverse
direction
(less likely to
produce
harm)
Translocation
• If all parts are transferred evenly, then no
harm.
• If also duplication or deletion, then
changes in genetic make-up.
INVERSION
• The chromosome
breaks in two
places, a piece of
the chromosome is
removed and the
chromosome
pieces remaining
rejoin.
Inversions
• Inversions, by definition, do not
involve loss or gain of
chromosomal material.
• chromosomal mutations (Mcgraw Hill)
• Click mutations
• Chromosome 10
has an inversion
INVERSION
Staining Chromosomes
• Chromosomes from the father of a
child... a portion of chromosome 11
(blue) has been transferred to
chromosome 1(yellow).