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Unformatted text preview: andom distribution
of orange and black patches
The white patches are due to
another gene (S). Human example:
Anhydrotic dysplasia is a disease that results in the absence of sweat
glands. Normal females are XX, heterozygous females are XX' and
have patches of skin with sweat glands and patches of skin without
sweat glands. Females that are X'X' do not have sweat glands.
Normal vs. Aberrations
at the chromosomal level)
See additional reading material:
additional reading material:
Normal Homologous Recombination
(occurs in testis and ovary) From
From diploid germ cells To haploid
Translocation 48 Insertion
Insertion 49 Deletion
Deletion Duplication 50 A representative karyotype and a photograph of a child
exhibiting cri-du-chat syndrome (46,5p-). In the karyotype, the
cri-du(46,5parrow identifies the absence of a small piece of the short arm
of one member of the chromosome 5 homologs.
th Affected individuals have wide-set eyes, a small head and jaw and are
moderately to severely mentally retarded and very short. When
When chromosome segregation fails…...
segregation Normal case acquire extra copy
eg. Chrom. 21:
Nondisjunction during the first and second meiotic divisions. In
both cases, some of the gametes that are formed either contain
two members of a specific chromosome or lack that chromosome.
After fertilization by a gamete with a normal haploid content,
monosomic, disomic (normal), or trisomic zygotes are produced. 53 The
The karyotype of a child with Down syndrome. In the karyotype,
three members of the G-group chromosome 21 are present,
Gcreating the 47
creating the 47,21+ condition.
condition Characteristics include decreased muscle tone asymmetrical skull
Characteristics include decreased muscle tone...
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- Winter '11