1. What Can Our Chromosomes Tell Us?

2. What are Chromosomes?
What do you see through the microscope lens?

3. What are Chromosomes?

4. What are Chromosomes? Compact spools of DNA. “DNA Packages”
We have 46 “packages” in each cell
23 from Father
23 from Mother

5. What do Chromosomes Look Like?
Very small
Best seen during mitosis

6. Why do Scientists Look at Chromosomes?
Diagnose or predict genetic disorders
Prenatal testing
Diagnosis can help patients receive medical treatment

7. How do you Read a Chromosome?
Three key features
Size
Banding Pattern
Centromere Position

8. What are Centromeres for?
Required for chromosome separation during cell division.
Attached to microtubules
Each chromosome has only one centromere.
Position helps scientists tell chromosomes apart.

9. What are Centromeres For?
Position of centromere can be describe in three ways:
Metacentric = near the center
Submetacentric = off-center therefore one arm is longer than the other
Acrocentric = resides very near one end

10. Centromere Positions

11. What is a Karyotype? Organized profile of a persons chromosomes
Chromosomes are arranged by number and size, from largest to smallest

12. Making a Karyotype Scientists take a picture of someone’s chromosomes
Each chromosome is then cut out and matched according to:
Size
Banding pattern
Centromere position

13. Making a Karyotype

14. Karyotypes and Genetic Disorders
Normal human karyotype
46 chromosomes
22 pairs of autosomes
2 sex cromosomes
What happens if…..
Too many or too few chromosomes?
Missing pieces of chromosomes?
Mixed up pieces of chromosomes?

15. Types of Mutations Deletion Inversion Translocation Nondisjunction
Duplication

16. Deletion
Breakage
A piece of the chromosome is lost

17. Inversion Chromosome segment breaks off Segment flips around backwards
Segment reattaches

18. Duplication
Occurs when a gene sequence is repeated

19. Translocation Involves two chromosomes that are not homologous
Part of one chromosome is transferred to another chromosome

20. Nondisjunction Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes

21. Chromosome Mutation Animation

22. Chromosome Mutations

23. What Can’t we see in a Karyotoype?
Individual DNA strands or genes.
The number of genes in any given area of a chromosome.
The presence or location of small mutations.

24. References http://learn.genetics.utah.edu/units/disorders/karyotype