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

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. 45,XX,rob(13,14) A Robertsonian translocation

Applications Chromosomes from the father of a retarded child... a portion of chromosome 11 (blue) has been transfered to chromosome 1(yellow).

Ideogram Show only one set of chromosomes