Abstract. The prolactin (PRL) gene regulates the egg production and incubation in laying chickens. Local chickens' reproductive systems will disrupt as a result of the incubation period activity, and they will lay fewer eggs. This study aimed to determine the prolactin gene polymorphism in IPB-D1 hens and its relationship to egg production. The polymorphism of the exon 5 prolactin gene was examined on 112 samples of the IPB-D1 chicken DNA collection from the Division of Animal Genetics and Breeding, Faculty of Animal Sciences, IPB University. By performing the phenol–chloroform method, the genomic DNA was obtained. A polymerase chain reaction (PCR) product with a size of 557 bp was produced as a result of the DNA amplification. Three single-nucleotide sequences were discovered. Three single-nucleotide polymorphisms (SNPs), g.7835A > G, g.7886A > T, and g.8052T > C, were found in exon 5 of the PRL gene. Each mutation was polymorphic and in Hardy–Weinberg equilibrium. The point mutation g.8052T > C significantly impacted the egg production of IPB-D1 chickens, according to the SNP association analysis on egg production, and may serve as a marker to enhance the selection for the features of egg production in IPB-D1 chickens.

<p class="JITV-ReferenceIsi">The prolactin gene (PRL) is a gene that controls the incubation and egg production in laying chickens. The nature of incubation will reduce egg production and disrupt the reproductive system in local chickens. The purpose of this study was to identify the polymorphism of prolactin genes in IPB-D1 chickens using the direct sequencing method. The polymorphism of the exon 5 prolactin gene was carried out on 46 samples of IPB-D1 chicken DNA which was a collection of the Division of Animal Genetics and Breeding, Faculty of Animal Science IPB. DNA sequences as a reference for designing exon 5 primers were obtained from the National Center for Biotechnology Information (NCBI) with the GenBank access code: AF288765.2. DNA extraction was carried out using the phenol-chloroform technique. DNA amplification resulted in a PCR product with a size of 557 bp. In this study, the genotype frequency, allele frequency, heterozygosity value and Hardy-Weinberg equilibrium were calculated. The results of the study found 5 SNPs in exon 5, namely g.7823A&gt;G, g.7835A&gt;G, g.7886T&gt;A, g.8052T&gt;C, and g.8069T&gt;C. All SNPs are polymorphic and in Hardy-Weinberg equilibrium except g.8052T&gt;C. The g.7823A&gt;G, g.7835A&gt;G, g.8052T&gt;C SNPs are synonymous mutations that do not change amino acids, while the g.7886T&gt;A and g.8069T&gt;C SNPs are non-synonymous that change amino acids. Both g.7886T&gt;A and g.8069T&gt;C SNPs are potential as a marker assisted selection for the characteristics of egg production in IPB-D1 chickens.</p>