1. Chromosomal mutation
A chromosomal mutation involves a change in the structure or number of chromosomes
4 types of chromosomal mutations:
Deletion: loss of all or part of a chromosome
Duplication: extra copy of all or part of a chromosome
Inversion: reverses the direction of parts of a chromosome
Translocation: part of one chromosome breaks off and attaches to another chromosome
Translocation- Found in a form of leukemia. Mutation called the Philadelphia chromosome- parts of chromosomes 9 and 22 break off and are translocated (exchanged position)

2. Karyotype: A photomicrograph of chromosomes arranged according to a standard classification

3. What each of the human chromosomes look like

4. In other words…
Chromosomes are digitally arranged so that they are matched with their homologue or “partner” chromosome.
Homologue chromosomes are the same size, shape, and carry the same genes, and one is inherited from each parent.
They are numbered according to size.

5. Sex determination with karyotype
The first 22 pairs are autosomes
Pair 23 are sex chromosmes—
XX = female
XY= male

6. Female and Male Karyotype

7. If there are chromosomal number abnormalities, how do they form?
Meiosis: the process of creating sperm or egg from a diploid cell
If there is a mistake when chromosomes are separating, then the resulting sperm or egg will have too many or too few chromosomes.

8. Prophase I: homologous chromosomes pairing into tetrads

9. Crossing over
The chromosomes during prophase I undergo crossing over, where parts of the homologues randomly switch places.

10. Metaphase I: tetrads align, along the metaphase plate

11. Anaphase I: homologous chromosomes separate from the metaphase plate
If chromosomes do not properly separate, this is called nondisjunction.
Nondisjunction leads to trisomy and monosomy disorders.

12. Telophase I: membranes form around the separated homologues

13. Prophase II: spindle fibers bind to the sister chromatids of each chromosome

14. Metaphase II: chromosomes align along the metaphase plate

15. Anaphase II: sister chromatids separate to opposite poles

16. Telophase II: nuclear membrane forms around newly separated chromatids
Note that each new nucleus formed has ½ the amount of DNA as the original cell.
These cells are haploid cells.

17. Nondisjunction
Other types of chromosomal mutations alter the number of chromosomes found in the cell.
Nondisjunction: The failure of homologous chromosomes or sister chromatids to separate during meiosis.
Produces gametes that have too many or too few chromosomes
Normal meiosis
Reg book: “not coming apart”

18. Nondisjunction

19. Disorders due to Nondisjunction
In humans, a zygote with 45 chromosomes has only one copy of a particular chromosome monosomy
In humans, a zygote with 47 chromosomes has three copies of a particular chromosome trisomy