Predict how the synaptic configurations of homologous pairs of chromosomes might appear when one member is normal and the other member has sustained a deletion or duplication.

Verified step by step guidance

1. Understand that synapsis is the pairing of homologous chromosomes during prophase I of meiosis, where chromosomes align gene by gene to form a synaptonemal complex.
2. Recognize that when one homologous chromosome has a deletion (a missing segment), the other homologous chromosome will have an unpaired region because there is no corresponding segment to pair with.
3. Predict that the chromosome with the deletion will cause a loop or bulge to form on the normal chromosome during synapsis, as the normal chromosome's extra segment has no counterpart on the deleted chromosome.
4. Similarly, if one homolog has a duplication (an extra segment), the duplicated region will loop out on the chromosome with the duplication to allow the rest of the chromosome to align properly with the normal homolog.
5. Conclude that these loops or bulges are visible under a microscope during meiosis and represent structural adjustments to maintain as much pairing as possible despite the deletion or duplication.

Key Concepts

Chromosome Synapsis

Synapsis is the pairing of homologous chromosomes during prophase I of meiosis, allowing for alignment and recombination. Proper synapsis ensures that homologs are closely paired along their lengths, facilitating genetic exchange and accurate segregation.

Chromosomal Deletions and Duplications

Deletions involve the loss of a chromosome segment, while duplications involve the repetition of a segment. These structural changes alter the length and gene content of one homolog, potentially disrupting normal pairing during meiosis.

Synaptic Configurations in Structural Heterozygotes

When one homolog has a deletion or duplication, synapsis can form loops or unpaired regions to accommodate length differences. For example, a duplication may cause a loop on the normal chromosome, while a deletion may cause a loop on the altered chromosome, reflecting misalignment.