A woman who sought genetic counseling is found to be heterozygous for a chromosomal rearrangement between the second and third chromosomes. Her chromosomes, compared to those in a normal karyotype, are diagrammed to the right.

What kind of chromosomal aberration is shown?

Verified step by step guidance

1. Step 1: Understand the types of chromosomal rearrangements. Common types include deletions, duplications, inversions, and translocations. Since the rearrangement involves two different chromosomes (chromosomes 2 and 3), focus on translocations.
2. Step 2: Identify whether the translocation is reciprocal or Robertsonian. Reciprocal translocations involve an exchange of segments between two non-homologous chromosomes without loss of genetic material, while Robertsonian translocations involve fusion of whole long arms of acrocentric chromosomes.
3. Step 3: Analyze the karyotype diagram to see if segments from chromosome 2 and chromosome 3 have been exchanged. If segments from both chromosomes have swapped places, this indicates a reciprocal translocation.
4. Step 4: Confirm that the woman is heterozygous for this rearrangement, meaning she has one normal set of chromosomes and one set with the translocation. This is typical for balanced reciprocal translocations where no genetic material is lost or gained.
5. Step 5: Conclude that the chromosomal aberration shown is a balanced reciprocal translocation between chromosomes 2 and 3, based on the exchange of segments without apparent loss or gain of genetic material.

Key Concepts

Chromosomal Rearrangements

Chromosomal rearrangements involve structural changes in chromosomes, such as deletions, duplications, inversions, or translocations. These changes can alter gene order or dosage and may affect gene function or cause genetic disorders. Understanding the type of rearrangement is key to interpreting karyotype differences.

Heterozygosity for Chromosomal Aberrations

Being heterozygous for a chromosomal rearrangement means one chromosome carries the alteration while the homologous chromosome remains normal. This can lead to complications during meiosis, such as abnormal pairing or segregation, potentially causing infertility or unbalanced gametes.

Types of Chromosomal Aberrations: Translocation vs. Inversion

Common chromosomal aberrations include translocations, where segments are exchanged between nonhomologous chromosomes, and inversions, where a chromosome segment is reversed within the same chromosome. Identifying whether the rearrangement involves two chromosomes or a segment flipped within one helps classify the aberration.