Poultry Genetics 101: Understanding DNA, Genes, and Traits in Chickens and Ducks: Fantasy Poultry Plus x Affordable Avian

Written by Katie Roesel of Fantasy Poultry Plus

Edits and corrections by Affordable Avian

Have you ever wondered what makes a chicken feathered in black while its sibling is white? Or how to predict the sex of a duckling before it hatches? The answers lie in genetics—a fascinating and essential part of poultry breeding.

In this post, we’ll break down the basics of poultry genetics in simple terms so you can better understand how traits are passed down, how sex is determined, and what terms like “homozygous” and “genotype” really mean.

What Is DNA?

DNA (short for deoxyribonucleic acid) is the molecule that carries the genetic instructions for how an organism develops and functions. DNA is structured like a twisted ladder—also called a double helix—with sides made of phosphate and sugar. Every living thing has DNA, and it’s the blueprint for all biological traits.

Basic Genetic Terms Explained

Gene:

A gene is a segment of DNA that holds the instructions for a specific trait, like feather color, comb type, or eye color.

Chromosome:

A chromosome is a structure made of tightly coiled DNA. These are the carriers of genetic material. Chickens have 78 chromosomes arranged in 39 pairs—one set from each parent.

Genotype:

A genotype is the genetic makeup of an organism—the DNA code behind its traits. It’s not always visible.

Example: Two birds may look identical but carry different hidden (recessive) genes.

Phenotype

A phenotype is the physical appearance of an organism—what you can actually see. Feather color, comb shape, and eye color are all parts of a bird’s phenotype.

Chromosomes in Poultry: Sex and Inheritance

There are two types of chromosomes:

1. Sex Chromosomes (Z and W)

In birds, sex is determined by the female, unlike in mammals.

• ZZ = Male

• ZW = Female

  
  

2. Autosomes

These are all the other chromosomes that aren’t involved in determining sex. They carry genes that affect physical traits and functions.

How Traits Are Passed Down

Each parent contributes one copy of every gene to their offspring. These gene pairs can be:

Homozygous

Both genes are the same.

Example: A bird with two black color genes is homozygous black.

Heterozygous

Each gene is different.

Example: A black Call duck carrying one black gene and one chocolate gene is heterozygous (often called “split to chocolate”).

Dominant and Recessive Genes

Genes come in dominant and recessive forms, also known as alleles.

• A dominant gene will always be expressed, even if only one copy is present.

• A recessive gene can only be expressed if the bird inherits two copies (homozygous).

Gene Combinations:

• Homozygous Dominant: Two dominant genes (trait is fully expressed)

• Homozygous Recessive: Two recessive genes (trait expressed)

• Heterozygous: One dominant, one recessive (dominant usually shows)

  
  

Co-Dominance: When Both Traits Show

Sometimes, both genes in a heterozygous pair can be expressed at the same time. This is called co-dominance.

Example:

• In Brahmas, a bird might inherit genes for both pea comb and single comb. You may see a comb that has traits of both.

• Both alleles are expressed, sometimes equally and sometimes with one showing more than the other.

  
  

Quick Recap: Poultry Genetics at a Glance

• DNA is the genetic blueprint of all life

• Genes are the instructions found on DNA

• Chickens have 39 pairs of chromosomes

• Sex chromosomes in birds:

  • ZW = Female, ZZ = Male

• Traits are inherited in pairs

• Homozygous = Two of the same gene

• Heterozygous = Two different genes

• Dominant genes override recessive ones

• Phenotype is what you see

• Genotype is the hidden genetic code

• Co-dominance means both genes show, to some degree
  

Final Thoughts

Understanding poultry genetics helps breeders make better decisions when selecting birds for specific traits like feather color, size, or even egg production. Whether you’re working with ducks, chickens, or any other bird, having a grasp on terms like genotype, phenotype, and homozygous will make you a more confident and informed breeder.

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