gebetics chapter 8
Terms
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- cytogenetics
- the field that involves the microscopic examination of chromosomes. Allowing the detection of individual with abnormal chromosomes number or structure.
- What are the main features that are used to identify chromosomes?
- The size, location of the centromere, banding patters.
- What two basic ways does chromosome variation occur?
- in structure and number
- The study of chromosome variation is important for what reasons?
- They can have a mjor effect on the phenotype of an organism, and the offspring, and is an important force in the evolution of species.
- Masaicism
- the presence of two or more cell lines in an individual, one or more of which are abnormal
- Euploidy
- changes in the entire set of chromosomes, and it occurs ocassionally in animals and frequently in plants
- Aneuploidy
- changes in individual chromosomes rather than in the complete set, regarded as abnormal conditions
- Monosomy
-
one homologue is missing
2n-1 - Trisomy
-
one extra homologue is present
2n+1 - tetrasomy
-
Two extra homologue are present
2n+2 - Double monosomy
-
Two different homologue are missing
2n-1-1 - Double trisomy
-
two different extra homologue are present
2n+1+1 - Nullisomy
-
a whole pair of chromosomes is missing
2n-2 - Haplo-IV in flies
- are monosomic and they are weaker and smaller
- Turner syndrome(Monosomy)
-
There is only one X present(they Y or the other X is missing)
45,X or 45,XO
45-50% are mosaics 46,XX/45,XO - Down syndrome(trisomy)
-
There is an extra 21 chromosome
46,XX or XY, +21 - Triplo IV in flies
- have no visible abnormalities
- Edwards syndrome(trisomy)
-
there is an extra 18 chromosome
46, XX or XY, +18
10% are mosaics - Patau syndrome(trisomy)
-
has an extra 13 chromosome
47, XX or XY, +13 - Klinefelter syndrome(trisomy)
-
there are extra sex chromosomes
47,XXY
10% are mosaics
*the more extra sex chromosomes the worst the syndrome is * - 47, XXX syndrome
- The more X the more deadly the syndrome. Usually benign consequences, under developed of genetalia, mental retardation
- Tetra-X and penta X karyotes
- are more severe than the 47 XXX syndrome
- 47, XYY condition
-
above average height
sub-average intelligence