Chromosomal disorders overview Flashcards
What are chromosomes?
Structures within cells that contains a person’s genes
What is the typical number of chromosomes?
- 46 (23 pairs)
2. One set from egg, one set from sperm
What are the first 22 pairs called? What are the final pair called?
22: Autosomes
Final: sex chromosomes
How are chromosomes studied? (2)
- Karyotype (image of all 46 chromosomes to identify abnormalities
- Newer: compare patient’s DNA to a typical DNA sample eg. prenatal testing
Why do chromosomal disorders occur?
Changes in either the number or structure of the chromosomes
How can the number of chromosomes be affected? (2)
- Missing one from a pair = monosomy
2. Has more than two chromsomes = trisomy
How can the structure of chromosomes be affected?
Material in an individual chromosome is disrupted or rearranged
Give 5 types of structural changes in chromosomes
- Deletion
- Duplication
- Translocation
- Rings
- Inversions
What is deletion?
Portion of the chromosome is missing or deleted
What is duplication?
Portion of the chromosome is duplicated - resulting in extra genetic material
What is translocation?
Portion of the chromosome is transferred to another
What are the 2 types of translocation?
Reciprocal: segments from two different chromosomes exchanged
Robertsonian: entire chromosome has attached to another at the centromere
What are rings?
Portion of the chromosome has broken off and formed a ring
What are inversions?
Portion of the chromosome has broken off, turned upside down and reattached
Genetic material is inverted
What are two types of cell division?
Meiosis
Mitosis
What is mitosis?
Results in two cells which are duplicates of the original cell
What is meiosis?
Results in cells with half the number of chromosomes (23)
What are 2 factors which can increase risk of chromosome abnormalities?
- Maternal age (errors in eggs genetic material)
2. Environment
