Karyotypes and Mutations. Karyotype An orderly display of magnified images of the individuals...
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Transcript of Karyotypes and Mutations. Karyotype An orderly display of magnified images of the individuals...
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).
One source:Amniocentesis• Take fluid
from amniotic fluid around the baby
• Can make a karyotype to see if there is a genetic disorder
Preparing a Karyotype
• 1. Use blood cells.
Essay: Preparing a Karyotype
• 2. Burst RBC (red blood cells) 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
Preparing a Karyotype
• 4. Add chemical (colchicine) to stop the chromatids in metaphase (stops spindle fibers from forming)
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
Other types of Karyotypes
Types of Karyotypes
• Fluorescent to detect a marker showing certain defect
Types of Karyotypes
• Colored dyes for certain chromosomes
Types of Karyotypes
• Ideogram: bands locate sites on chromosome
Normal Karyotype
• WHY?• Is it a Male or a female?
Down Syndrome Karyotype
• Trisomy 21
Down Syndrome
• Trisomy 21
• Folds over eyes
• Sluggish muscles
• Mental Problems
Down Syndrome
• The most common chromosome number abnormality
• Round face
• flattened nose bridge
• small, irregular teeth
Down Syndrome
• Short Stature
• heart defects
• susceptibility to respiratory infection , leukemia and Alzheimer’s
Does the mother’s age matter?
• As the age of the mother increases above 30, the frequency of Trisomy 21 also increases
Nondisjunction
• Uneven distribution of chromosomes in cell division
Abnormal Sex Chromosomes• 47 XXY syndrome
• male
• testes small (sterile)
• breast enlargement
• feminine body contours
• Klinefelter’s
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
30
Abnormal Chromosome Numbers
• Aneuploidy
– Missing or extra chromosome
• Polyploidy
– Extra set of chromosomes
– Usually lethal
– Common in cancer
– Common in plants
Nondisjunction
What about…
• MUTATIONS?
DELETION
Fragment of the chromosome is lost
Duplication
Fragment of one chromosome attaches to a homologous chromosome
Translocation
Fragment reattaches in reverse direction (less likely to produce harm)
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.
INVERSION 46,XY,inv(16)
• The left one is normal and the right one is inverted near the centromere.
45,XX,rob(13,14) A Robertsonian
translocation
(an end to end fusion of #13 and #14) There is no net gain or loss of genetic material in this person so they would have a normal phenotype.
Applications
• Chromosomes from the father of a retarded child... a portion of
• chromosome 11 (blue) has been
• transfered to chromosome 1(yellowyellow).
Ideogram
Show only one set of chromosomes