Definition

AZFb is a subregion located in the Yq11 region of the Y chromosome, with a classic complete deletion of approximately 6.23 megabases; this deletion arises from non-allelic homologous recombination (NAHR) between identical sequence blocks. The classic AZFb deletion completely removes six protein-coding genes and is almost always associated with meiotic arrest (arrest of spermatogenesis at the meiotic stage); mature sperm are absent in the testes. Partial deletions with different breakpoints can show more variable presentations such as cryptozoospermia or oligozoospermia.

Gene/region examined

SRY - AZFb region

Method

Gel electrophoresis

Accepted sample types

EDTA blood

Inheritance

Y-linked, and typically a de novo event. Natural father-to-son transmission is not possible due to infertility; if sperm production is partially preserved, the deletion can be passed to sons born via ICSI.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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