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Karyotyping
• Karyotype – Size-ordered chart of the metaphase
chromosomes of an individual cell
• Chromosomal aberration– A mutation that is large enough to see under
a light microscope
Changes in Sex Chromosome Number
• Y chromosome-determines maleness. • SRY gene produces a testis-determining
factor• Caused by non-disjunction
Non-disjunction in Sex Chromosomes
Y chromosome-determines maleness.
Results of non-disjunction?:
XXX
XXY
XYY
X0
0Y
Survivable with problems
Survivable with problems
Survivable with problems
Survivable with problems
Lethal
Non-disjunction in Sex Chromosomes
• Turner Syndrome --XO
• Klinefelter Syndrome—XXY
• Poly-X Females---XXX
• Jacobs Syndrome---XYY
• Mutation– a permanent genetic change.
• Chromosome mutation--change in chromosome structure.
• Types:– Inversion– Translocation– Deletion– Duplication
Changes in Chromosome Structure
• Traits controlled by genes on the X or Y chromosomes are sex-linked although most are unrelated to gender.
• An allele on the X chromosome that is in the region where the Y chromosome has no alleles will express even if recessive; it is termed X-linked.
• A female would have to have two recessive genes to express the trait; a male would only need one.
Sex-Linked Traits
X-Linked Alleles• The key for an X-linked problem shows the
allele attached to the X as in:• XB = normal vision
• Xb = color blindness. • Females with the genotype XBXb are
carriers because they appear to be normal but each son has a 50% chance of being color blind depending on which allele the son receives.
• XbXb and XbY are both colorblind.
http://perth.uwlax.edu/faculty/howard/BIO101/DNA&translation/sld002.htm
Diana
http://brie.medlabscience.med.ualberta.ca/de/genetics/70gen-hemophil.html