Karyotyping Chromosomes are extracted from a cell, stained, photographed and paired for genetic...
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Transcript of Karyotyping Chromosomes are extracted from a cell, stained, photographed and paired for genetic...
Karyotyping
Chromosomes are extracted from a cell, stained, photographed and paired for genetic analysis in the lab.Karyotypes are used to identify chromosomal disorders.
• Karyotypes are prepared with metaphase cells.
• 46 chromosomes identify a karyotype as human.
• 44 of the chromosomes are called autosomes
• 2 of the chromosomes are sex chromosomes– XX for females– XY for males
Fertilization
Males can contribute an X or a Y.
Females can only contribute an X, because they have 2X’s.
Who determines the sex of the zygote (offspring)?
Normal Human Karyotype
Nondisjunction• When an error occurs in
meiosis and the homologous chromosomes fail to separate it is called nondisjunction.
• Nondisjunction results in the wrong number of chromosomes in a gamete.
• This wrong number of chromosomes leads to a disorder.
Trisomy 21– Down Syndrome
• Characteristic facial features, short stature; heart defects • Susceptibility to respiratory disease, shorter lifespan • Prone to developing early Alzheimer's and leukemia • Often sexually underdeveloped and sterile • Usually some degree of mental retardation. • Down Syndrome is sometimes related to the age of
mother, but can also be the result of nondisjunction of the father's chromosome 21.
Down Syndrome Trisomy 21
Klinefelters XXY
• Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence.
Triple X Syndrome XXX
• females. • 1:1000 live births• healthy and fertile• usually cannot be
distinguished from normal female except by karyotype
Turners Syndrome XO
• 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)
Gorilla karyotype
sex-specific chromosomes, sex chromosomes, occur in many species
Non-sex chromosomes are called autosomes
Mouse Karyotype