Lesson 8: Chromosomal Abnormalities

Quantitative Abnormalities:

Changes in the number of

chromosomes.

Qualitative Abnormalities:

Changes in chromosome structure.

1. Aneuploidy

2. Polyploidy

Types of Quantitative Abnormalities

Aneuploidy

Abnormal number of

chromosomes.

Monosomy

missing one chromosome

Trisomy

extra chromosome

Polyploidy

Extra sets of chromosomes.

Triploidy:

Three sets of

chromosomes

Tetraploidy:

Four sets of

chromosomes.

● Deletion

● Duplication

● Inversion

● Translocation

● Ring Chromosomes

Qualitative Abnormalities

Deletion

Loss of a chromosome segment

Duplication

Repetition of a chromosome segment

Inversion

Segment reverses

direction; may disrupt function.

Translocation:

Exchange or fusion

of chromosome segments

Ring Chromosomes:

Ends of a

chromosome join, forming a ring

Trisomy 13 (Patau Syndrome)

Microcephaly, cleft palate,

congenital heart defects.

● Often leads to early death.

Trisomy 18 (Edwards Syndrome):

● Severe developmental

issues, organ defects.

● Median survival: ~1 year.

Trisomy 21 (Down Syndrome):

● Causes intellectual disability,

physical features, higher

leukemia and Alzheimer’s

risk.

● Median survival: 47 years.

Fluorescence In Situ

Hybridization (FISH):

Detects

specific DNA sequences.

Chromosomal Microarray

Analysis (CMA):

Identifies microdeletions/duplications.