Chromosome G-banding

When treated with stains, chromosomes often display banded patterns, alternating between light and dark, which happens especially during metaphase where the more condensed segments of DNA tend to stain darkly. Therefore, chromosomes can be treated with different methods including G-banding, Q-banding, R-banding, C-banding, NOR-banding or T-banding.

The most commonly used in human cytogenetic analysis is G-banding, allowing between 400 and 600 bands to appear along the length of the whole chromosome in metaphase. This technique uses chromosomes pre-treated with salt or a proteolytic enzyme like trypsin and then stained with Giemsa, which highlights preferentially regions rich in adenine and thymine. Also, the darker stained regions usually are heterochromatic (non functional genes) and late-replicating and the lighter regions are euchromatic (actively transcribed) and early-replicating.

The importance of banding techniques is to diagnose chromosomal anomalies such as chromosome breakage, loss, duplication or inverted segments by identifying unique banding patterns.

Bioquímica 2º ano

Grupo 13:

Adriana Gomes

Andreia Campos

Bárbara Nogueira

Patrícia Machado