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