1. Abnormal Meiosis

2. What each of the human chromosomes look like

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

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
This karyotype has 23 exact pairs, which means the person is female.
Note that #23 chromosomes are both X.

6. Normal human male
Note that #23 chromosomes are X and Y.

7. Is this person female or male?

8. Is this person female or male?

9. Trisomy 21 Abnormality shown in karyotype
Note that there are three copies of #21 chromosome.
This person has Down Syndrome.

10. Photos of Down Syndrome patients from the National Down Syndrome Society

11. Correlation between mother’s age and Trisomy 21 incidence

12. Monosomy X Abnormality shown in karyotype
Note this person only has 1 copy of the X chromosome.
This female has Turner’s syndrome.
Occurs 1 in 2500 females

13. XXY Male (Extra X)
Affected individuals have at least two X chromosomes and at least one Y chromosome.
The most common sex chromosome disorder
This male has Klinefelter’s syndrome.
Occurs 1 in 500 males

15. How are DNA samples obtained for karyotypes?

16. Amniocentesis: obtaining amniotic fluid which has cells from the fetus

17. Chorionic villi sampling: removing cells from the chorion with fetal tissue

18. 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.