Errors and Exceptions in Chromosomal Inheritance

1. Errors and Exceptions in Chromosomal Inheritance By: Ryan and Victor

2. The Chromosomal Theory of Inheritance • The chromosomal theory of inheritance is the idea that genes, the units of heredity, are physical in nature and are found in the chromosomes. • Chromosomes are seen in all dividing cells and are passed from generation to generation.

3. Errors in Chromosomal Inheritance • When chromosomes are passed down to the next generation during replication, some abnormalities may occur. • These abnormalities typically occur as a result of errors in meiosisor mitosis. • Nondisjunction, deletion, duplication, inversion, and translocation are the main causes of error in chromosomes.

4. Nondisjunction • Nondisjunction is the uneven separation ofchromosomes during the process of meiosis 1 and meiosis 2 • The abnormality in chromosome number found in the cells is called aneuploidy

5. Deletion • Deletion occurs when a segment of the chromosome is deleted which also changes the whole chromosome • Without the correct chromosome structure, the offspring can be deformed or end up dying

6. Duplication • Duplication occurs when a segment of the chromosome is repeated • The broken off segment that caused deletion can be attached to the sister chromatid • Advantage: If extra DNA codes for the production of protein, our bodies will benefit from the excess • Disadvantage: If extra DNA codes for a disease, the person is more likely to get the disease

7. Inversion • Inversion occurs when a segment of DNA breaks off and reattaches itself backwards • There are no drastic consequences in inversion but there are suspicions that it may cause an increased risk to miscarriages

8. Translocation • Translocation occurs when a segment of the chromosome joins or attaches to a non-homologous chromosome • This event can be interchangeable with the non-homologous chromosome (the non-homologous can exchange its segment)

9. Can you tell which type of error is shown? Explain your answer.