1. Karyotypes

2. Karyotypes
Chromosomes in a cell are visible only when the cell is dividing
At metaphase stage chromosomes are fully condensed and easy to see.
Metaphase spreads are selected and photographed in order to analyze
The chromosomes are then arranged in homologous pairs.

3. Karyotypes
The homologous pairs are placed in order of descending size. The sex chromosomes are placed at the end.
A picture of chromosomes arranged in this way is known as a karyotype.

4. Metaphase Chromosomes (a) Arranged Into a Karyotype (b)
(a) A metaphase array of chromosomes as viewed in the microscope. (b) The computer-derived karyotype. Note that the computer has straightened the chromosomes as they were processed and arranged into a karyotype.

5. Human Chromosomes
A “normal” human carries 23 PAIRS of chromosomes (1 set came from the mother, 1 set came from the father)
22 of these sets are called autosomes (or “self chromosomes”)
1 set are the sex chromosomes
A female carries two X chromosomes (XX)
A male carries an X chromosome and a Y chromosome (XY)
Mazen Zaharna Molecular Biology 1/2009

6. Labeling a Karyotype
To label a karyotype correctly, first list the number of chromosomes found in the karyotype. Ex. 46
Secondly, list the type of sex chromosomes found in the karyotype. Ex. XX
Lastly, list the any abnormalities at the appropriate chromosome number.

7. Normal Human Female: 46, XX
Normal Human Male: 46, XY

9. Size Human chromosomes range in length from 51 million to 245 million base pairs. They are numbered from largest to smallest

10. Position of centromere metacentric
submetacentric
acrocentric

11. different banding resolution
Banding pattern each chromosome has a unique banding pattern Chromosomal bands are alternating light and dark segments that result from various staining procedures.

12. Chromosome abnormalities
Numerical
Monosomy
one member of a chromosome pair is missing
Trisomy
one chromosome set consists of 3 copies of a chromosome
Structural
-Translocations
-Inversions
-Deletions
-Duplications
Mazen Zaharna Molecular Biology 1/2009

13. Translocation
Deletion
Insertion
Inversion
Isochromosome
Ring
chromosome
Derivative

16. 47,XY+5(Del)9