1. What are they?? How do we use them?
Karyotypes
What are they??
How do we use them?

2. Karyotypes – What are they?
A karyotype is a photo of the chromosomes in a cell that shows the chromosomes arranged by size.

3. Karyotypes – What are they?
A normal human karyotype should have 46 chromosomes.
23 pairs of homologous chromosomes
The last pair (pair 23) determines if the human is male or female
Also known as the sex chromosomes

4. Normal Karyotype--male
A normal male karyotype has 1 X chromosome and 1 Y chromosome in the 23rd pair
Male = XY

5. Normal Karyotype--female
A normal female karyotype has 2 X chromosomes in the 23rd pair
female = XX

6. Is this person female or male?

7. Karyotypes – How do we use them?
Karyotypes can reveal genetic disorders by showing changes in chromosome number or large deletions in chromosomes

8. How are DNA samples obtained for karyotypes?

9. If there are chromosomal number abnormalities, how do they form?
If there is a mistake when chromosomes are separating during meiosis, then the resulting sperm or egg will have too many or too few chromosomes.
This is called Nondisjunction

10. Nondisjunction

11. So, what do you look for when examining a karyotype?
Are there 46 chromosomes?
Are there 2 identical pairs of each chromosome and 2 sex chromosomes?
Are there any rearrangements between chromosomes or large deletions?

12. Trisomy 21 or Down Syndrome
Caused by nondisjunction
The #21 chromosomes ends up with 3 chromosomes instead of 2
Humans with Trisomy 21 have 47 chromosomes total

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

14. Turners syndrome Caused by nondisjunction
There is only 1 X chromosome and no Y chromosome
Humans with Turners syndrome have 45 chromosomes total

15. Klinefelter syndrome Caused by nondisjunction
There are 2 X chromosomes and 1 Y chromosome
Humans with Klinefelter syndrome have 47 chromosomes total

16. Is this a normal karyotype??
Male or Female?
Is this a normal karyotype??
XXY Male (Extra X)

17. What we can’t see Individual DNA strands or genes
The number of genes in any given area of a chromosome.
The presence or location of small mutations. (Scientists cannot predict diseases caused by small mutations within genes.

18. Other chromosomal disorders that can arise?

19. Problems with chromosomes
Duplication: copied parts of chromosome A B C D A B C D

20. Problems with chromosomes
Deletion: missing parts of chromosome A B C D A D

21. Deletion—18 Q Deletion Syndrome
Caused by deletion
Parts of the #18 chromosomes have been deleted

22. Problems with chromosomes
Inversion: parts of chromosome flipped A B C D A C B D

23. Chromosomal mutations
Deletion
Duplication
Inversion
Translocation

24. Human genetic disorders
Sometimes the alleles inherited contribute to disorders, or diseases, and not from the number or shape of the chromosomes.
Types include:
Sex-linked: genes found on X or Y chromosome
Recessive: requires 2 allele copies to express disorder
Dominant: requires only 1 allele copy to express disorder

25. Recessive disorders

26. Dominant disorder