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Gene Duplication and Divergence

Gene Duplication and Divergence

The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of the genes in bacteria, archaebacteria, and eukaryotes was generated by gene duplication and divergence, indicating its critical role in evolution.
The duplicated copies of the gene are called Paralogs. Paralogs with similar sequences and functions form a gene family. Across several species, a large number of gene families are characterized.

Exon Recombination

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The evolution of new genes is critical for speciation. Exon recombination, also known as exon shuffling or domain shuffling, is an important means of new gene formation. It is observed across vertebrates, invertebrates, and in some plants such as potatoes and sunflowers. During exon recombination, exons from the same or different genes recombine and produce new exon-intron combinations, which might evolve into new genes.
Exon shuffling follows “splice frame rules.” Each exon has three reading...

Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes

Pharmacogenetics of Phase I Enzymes: Cytochrome P450 Isozymes

Cytochrome P450 (CYP450) enzymes are a superfamily of heme-containing monooxygenases that play a pivotal role in Phase I drug metabolism by catalyzing oxidation and reduction reactions.These enzymes transform lipophilic xenobiotics into more hydrophilic metabolites, facilitating subsequent Phase II conjugation and eventual excretion. The CYP450 family is classified into families (e.g., CYP1–CYP3) and subfamilies (e.g., CYP2A, CYP2C), based on amino acid sequence homology.CYP450 isoenzymes,...

Gene Families

Gene Families

Gene families consist of groups of genes proposed to have originated from a common ancestor. Typically these arise through events in which a gene or genes are mistakenly duplicated during cell division. Unlike their parent genes (which are subject to selection pressure to maintain function), these gene copies do not need to preserve their sequences and may evolve at a relatively faster rate.
Occasionally these regions can be adapted to take on new roles within the organism, becoming novel genes...

Karyotyping

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X and Y Chromosomes

X and Y Chromosomes

Among mammals, the gender of an organism is determined by the sex chromosomes. Humans have two sex chromosomes, X and Y. Every human diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A human female has two X chromosomes, while a male has one X chromosome and one Y chromosome.
The germline cells such as egg and sperm cells carry only half the number of chromosomes, i.e., 22 autosomes and one sex chromosome. All eggs have an X chromosome, while sperm cells can carry an X or...

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CRISPR Gene Editing Tool for MicroRNA Cluster Network Analysis

CRISPR Gene Editing Tool for MicroRNA Cluster Network Analysis

Published on: April 25, 2022

Analysis of the duplicated human C4/P450c21/X gene cluster.

W L Miller¹, S E Gitelman, J Bristow

¹Department of Pediatrics, University of California San Francisco, San Francisco, CA 94143-0978, USA.

The Journal of Steroid Biochemistry and Molecular Biology

|January 6, 2012

Summary

This summary is machine-generated.

Gene duplications and deletions are common in the P450c21 gene region. Understanding the XA gene

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Area of Science:

Genetics
Molecular Biology
Genomics

Background:

The P450c21 gene locus in the human genome exhibits high rates of duplication, deletion, and rearrangement.
This locus contains at least six genes, including C4A, P450c21A, XA, C4B, P450c21B, and XB.

Purpose of the Study:

To investigate the mechanisms and timing of gene duplication within the P450c21 gene cluster.
To analyze the structure of the XA gene and its flanking regions to understand gene organization.
To correlate gene structure with disease-causing lesions in the P450c21B gene.

Main Methods:

Sequence analysis of the XA gene, 5' flanking DNA of C4A, and part of the XB gene.
Southern blotting to analyze P450c21B alleles.

Main Results:

The gene cluster duplication occurred via nonhomologous recombination at a CAAG tetranucleotide, likely after mammalian speciation.
The XA gene is expressed in the human adrenal gland as a 2.6 kb RNA, though its function is unknown.
Approximately 76% of disordered P450c21B alleles have microconversions, with the remainder being deletions or large gene conversions.

Conclusions:

The P450c21 gene cluster's duplication mechanism and timing provide insights into genome evolution.
Understanding the XA gene's anatomy aids in the genetic analysis of P450c21B-related diseases.
The high frequency of microconversions in P450c21B alleles suggests a significant role in genetic disorders.