1. Chromosomal Disorders
What happens when meiosis goes wrong?

2. Karyotype

3. Human Chromosomes Humans have 46 chromosomes arranged in 23 pairs
Two sex chromosomes- determine an individual’s sex
Females have two copies of the large X chromosome
Males have one X and a smaller Y chromosome

4. Human Chromosomes
The remaining 44 chromosomes are known as autosomal chromosomes or autosomes
Males and females are born in a roughly 50:50 ratio
All human egg cells carry a single X
Half of all sperm carry an X and the other half carry a Y

5. Male or Female???

6. Types of Mutations
Mutations effects vary. One factor is the type of cell if affects…
GERM CELLS-
Cells that undergo meiosis to produce egg and sperm cells (in ovaries and testes)
SOMATIC CELLS-
All the “other” body cells that only do mitosis

7. How would this affect the person differently?

8. Types of Mutations
Chromosomal mutations involve changes in the number or structure of chromosomes
Can lead to diseases or disorders… or (more rarely) can be beneficial

9. Chromosomal Mutations
Examples:
Entire chromosome mutation = nondisjunction
“chunk” of a chromosome mutation= listed to the right in diagram (insertion, deletion…)

10. Gene/DNA Mutations
Gene/DNA mutations involve changes in ONE nucleotide
Ex’s- Point and Frameshift Mutations

11. Chromosomal Mutations
Entire chromosomes encounter mutations as well
There are four types:
Deletion
Inversion
Insertion
Translocation
A B C
D E
Chromosome
Gene

12. Deletion Before mutation After mutation
A B C
D E
A C
D E
Occurs when a single break causes a chromosome to lose an end piece or when two simultaneous breaks lead to loss of internal segment

13. Inversion Before mutation After mutation
A B C
D E
A B C
E D
Occurs when a part of the chromosome breaks off and is reinserted backwards

14. Insertion Before mutation After mutation
A B C
D E
After mutation
B C
A B C B C
D E
Occurs when a part of the chromosome breaks off & re-attaches to the same chromosome resulting in a duplication of genes

15. Translocation Before mutation After mutation
A B C
D E
F G H
After mutation
F A B C
D E G H
Occurs when a part of one chromosome breaks off & attaches to a non-homologous chromosome
F G H
F G H
F G H

16. Can you spot what is wrong with this karyotype?

17. Creates gametes with the wrong number of chromosomes!
Nondisjunction
Homologous chromosomes fail to separate during meiosis I
Sister chromatids fail to separate during meiosis II OR
Creates gametes with the wrong number of chromosomes!

19. Changes in chromosome structure
Deletion
Part of a chromosome is lost during cell division
Chromosome is missing genes
Duplication
Region of chromosome is repeated
Translocation
Piece of a chromosome moves to another chromosome