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What is a Karyotype ?. Honors Biology Monkemeier/ Germinario. Karyotype. Pronunciation: “Carry” “o” “type” Also Known As: chromosome test, chromosome analysis
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What is a Karyotype? Honors Biology Monkemeier/ Germinario
Karyotype • Pronunciation: “Carry” “o” “type” • Also Known As: chromosome test, chromosome analysis • A karyotype is a picture of all the chromosomes from an individual’s cells. A karyotype is a test used to check for chromosome abnormalities
How is a Karyotype made? A picture of a person’s chromosomes is created by • staining the chromosomes with a special dye, • photographing them through a microscope and • arranging them in pairs from longest to shortest.
What information can be obtained by analyzing a karyotype? • A karyotype gives information about the number of chromosomes a person has, the structure of their chromosomes and the sex of the individual.
Abnormalities on Karyotype – Chromosome Numbers • Monosomy: Mono = one Somy = body • Monosomy: Only one chromosome is found on the line in the karyotype where a pair of chromosomes should be found.
Monosomy Monosomy 13 Monosomy 23 or Turner’s Syndrome
Trisomy – One chromosome too many on a line where a pair of chromosomes is expected.
Abnormalities in Chromosome Numbers - Common • Down syndrome(trisomy 21): • Patau syndrome (trisomy 13): serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months. • Edward's syndrome (trisomy 18): almost every organ system affected 1:10,000 live births. Children with full Trisomy 18 generally do not live more than a few months.
Abnormal Number of Chromosomes • Klinefelter syndrome: 47, XXY males. Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence. • 47, XYY males: Individuals are somewhat taller than average and often have below normal intelligence. At one time (~1970s), it was thought that these men were likely to be criminally aggressive, but this hypothesis did NOT stand up to testing and has been disproven over time.
Abnormal Number of Chromosomes • Trisomy X: 47, XXX females. 1:1000 live births - healthy and fertile - usually cannot be distinguished from normal female except by karyotype • Monosomy X (Turner's syndrome): 1:5000 live births; the only viable monosomy in humans - women with Turner's have only 45 chromosomes!!! XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% of these fetuses die before birth)
Karyotypes also show abnormal chromosomes. • Crit du Chat is a disorder shown on a karyotype. Note that one of the chromosomes on pair number 5 is missing a piece.