Name: gene masking in rabbit fur color
Uploaded: 2026-08-26T08:19:53.090Z
Duration: 2 min 31 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Biology

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

9-12.B.3.11.b

Epistasis

&#xA0;In eukaryotic cells, genes at different loci can interact to influence traits. In some cases, one gene can mask or modify the effect of another gene. This type of gene interaction is called epistasis.For example, epistasis appears in rabbit coat color. Several genes affect rabbit pigmentation, including the tyrosinase gene, or TYR, and the tyrosinase-related protein 1 gene, or TYRP1.The TYR gene corresponds to the classical C or albino locus. This gene helps control an early step in melanin production.Rabbits that inherit two recessive TYR alleles cannot produce melanin pigment, so their coats appear white. Rabbits carrying at least one functional dominant TYR allele, either homozygous dominant or heterozygous, can produce pigment normally and appear black or brown.The tyrosinase-related protein 1, or TYRP1 gene, corresponds to the B or brown locus. At this locus, the dominant allele leads to black pigment, while the recessive allele leads to brown, or chocolate-colored, fur.When considering only these two coat-color genes, TYR and TYRP1, rabbits that are heterozygous at both loci appear black.When these rabbits mate, some offspring inherit two recessive TYR alleles and develop white fur, regardless of which TYRP1 alleles they inherit, because the recessive TYR genotype completely stops melanin production.In these rabbits, the homozygous recessive TYR genotype stops melanin production, so the TYRP1 gene cannot affect the visible coat color.This is an example of recessive epistasis, where the recessive TYR genotype masks the effect of the black or brown pigment controlled by the TYRP1 gene.In this type of cross, the offspring may show a phenotypic ratio of 9 black to 3 brown to 4 white. This ratio is characteristic of recessive epistasis.

epistasis

In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence phenotypes in a phenomenon called epistasis. For example, rabbit fur can be black or brown depending on whether the animal is homozygous dominant or heterozygous at a TYRP1 locus. However, if the rabbit is also homozygous recessive at a locus on the tyrosinase gene (TYR), it will have an unshaded coat that appears white, regardless of its TYRP1 alleles. This is an example of recessive epistasis and demonstrates that most biological systems involve many genetic elements that interact in multiple and complex ways.

<h4>Epistasis</h4>

Although Mendel chose seven unrelated traits in peas to study gene segregation, most traits involve multiple gene interactions that create a spectrum of phenotypes. When the interaction of various genes or alleles at different locations influences a phenotype, this is called epistasis. Epistasis often involves one gene masking or interfering with the expression of another (antagonistic epistasis). Epistasis often occurs when different genes are part of the same biochemical pathway. The expression of a gene might depend on a gene product in the same biochemical pathway.

<h4>Tyrosinase and TYRP1</h4>

One example of epistasis is fur pigmentation in rabbits. Many genes affect a rabbit&#x2019;s fur color, including one called tyrosinase (TYR). Animals homozygous dominant or heterozygous at a tyrosinase locus will produce colored coats, while homozygous recessive rabbits develop unpigmented coats that appear white. Fur color is also partially established by another gene called tyrosinase-related protein 1, or TYRP1. The dominant allele produces black fur, and the recessive allele produces brown or chocolate fur.

Disregarding other factors involved in coat color, rabbits heterozygous at both loci will have black fur. However, their offspring that inherit two recessive tyrosinase alleles will have white, unpigmented fur, regardless of which TYRP1 alleles they inherit. This is an example of recessive epistasis because the recessive TYR alleles mask or interfere with the production of a black or brown coat. In this case, TYR is epistatic to TYRP1.

<h4>The Complexity of Genetic Interactions</h4>

The study of epistatic interactions allows researchers to understand how different species developed coat colors to suit unique environments. In general terms, it helps determine the functional relationship between genes, the ordering of genes in a pathway, and how different alleles quantitatively impact phenotypes. As such, since the concept of epistasis was introduced, it has become increasingly clear that most biological systems involve many genetic elements that interact with one another in multiple and complex ways.

In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence ...

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Education

JoVE Core

Genetics

Classical and Modern Genetics

KEY TERMS AND CONCEPTS

gene masking in rabbit fur color

Epistasis describes how one gene can mask or change the effect of another gene. In high school genetics, this helps explain why many traits do not follow a simple single-gene pattern. Instead, alleles at different locations can work together to shape the final phenotype.

Mendel studied seven unrelated pea traits, but most traits involve multiple gene interactions. Epistasis often happens when one gene interferes with the expression of another gene. It can also occur when genes are part of the same biochemical pathway, where one gene product depends on another step in that pathway.

Rabbit coat color is a clear example. The tyrosinase gene, or TYR, helps determine whether a rabbit produces pigment. Rabbits that are homozygous dominant or heterozygous at the TYR locus make colored coats, while homozygous recessive rabbits have unpigmented coats that appear white.

Another gene, TYRP1, also affects fur color. The dominant TYRP1 allele produces black fur, and the recessive allele produces brown or chocolate fur. If a rabbit is heterozygous at both loci, it will have black fur, assuming other coat-color factors are not involved.

Recessive epistasis appears when two recessive TYR alleles hide the TYRP1 result. Offspring with this TYR genotype have white, unpigmented fur no matter which TYRP1 alleles they inherit. In this case, TYR is epistatic to TYRP1 because it masks the other gene’s effect.

Studying epistatic interactions helps researchers understand how species developed coat colors that fit their environments. It also helps identify the functional relationship between genes and the order of genes in a pathway. More broadly, epistasis shows that many biological systems depend on many genetic elements working together in complex ways.

Gene Masking in Rabbit Fur Color

genetic lingo

Genotype, Phenotype, and Inheritance

Genotype, phenotype, and inheritance help explain how traits and disease risk are passed from parents to offspring. In diploid organisms, including humans, most other animals, and many plants, somatic cells carry a duplicate set of chromosomes. These chromosome pairs are homologous, with similar length, centromere position, and gene locations. Diploid organisms inherit two versions of each gene, one from each parent. These versions are called alleles, and they sit at the same relative locus,...

punnett squares

Punnett Squares for Predicting Traits

Punnett squares help predict which traits offspring may inherit from two parents. They show possible genotypes, which are pairs of alleles, and can also show the chance of a phenotype, or visible trait, when the inheritance pattern is known. These grids work best for traits controlled by a single gene locus and passed on independently during meiosis. Punnett squares were developed in the early 1900s by Reginald Punnett. His work came after Gregor Mendel’s pea plant experiments revealed the...

monohybrid crosses

Mendel’s Pea Plant Inheritance Ratios

Gregor Mendel used pea plants to study how traits are passed from parents to offspring. His breeding experiments in the 1850s and 1860s showed that inheritance follows clear patterns. He crossed true-breeding plants that differed in one trait and found that dominant traits can hide recessive traits. Mendel focused on seven pea plant traits, and each trait had two forms controlled by a single gene locus. He noticed that true-breeding plants always produced offspring with the same phenotype, or...

dihybrid crosses

Mendel's Law of Independent Assortment

Mendel’s law of independent assortment explains how two traits can be inherited separately. Gregor Mendel tested this idea with pea plants that differed in two characteristics, such as pea color and pea shape. He used true-breeding parents that were homozygous for both traits but showed different phenotypes. In one example, Mendel crossed round, yellow peas with wrinkled, green peas. The parental generation had RRYY and rryy genotypes. Their first-generation offspring were all dihybrids,...

law of segregation

Mendel’s Pea Cross Ratios

Mendel’s pea plant crosses show how traits can disappear in one generation and return in the next. When he crossed plants, one parental trait sometimes seemed to vanish in the F1 generation and reappear in the F2 generation. Mendel used this pattern to explain why some traits are dominant and others are recessive. He proposed that traits are controlled by alleles, which are different versions of a gene. An organism inherits two copies of each gene, one from each parent. In his model, a...

law of independent assortment

Mendel’s Dihybrid Cross and Trait Ratios

Mendel’s dihybrid cross shows how two traits are inherited at the same time. A dihybrid cross is a cross in which both parents are homozygous for two distinct traits, and the F1 generation is heterozygous for both traits. Mendel used pea plants with round yellow peas and wrinkled green peas as an example. One parent had genotype YYRR, and the other had genotype yyrr. In the F1 generation, every plant showed the dominant traits, so the plants were YyRr and had yellow, round peas. The F2...

test cross

Using Test Crosses to Identify Genotypes

Test crosses are used to identify the genotype of an organism with a dominant trait. A genotype is the pair of alleles inherited for a gene, and alleles are different forms of the same gene. In diploid organisms, including humans, each gene usually has two alleles, one from each parent. An allele is recessive when its effect is hidden by another allele at the same gene location. Pea plants provide a clear example with flower color. White flowers are recessive, because one copy of the purple...

probability laws

Inheritance Risk with Sum and Product Rules

Inheritance risk can be calculated with the sum rule and the product rule. The sum rule applies to mutually exclusive events, or events that cannot happen at the same time. The product rule applies to independent events, or events that do not affect one another. These rules describe theoretical probability, which is the chance of an event before it happens. Empirical probability is different because it is based on events that have already occurred. These probability rules are useful in...

pedigree analysis

Reading Family Traits in Pedigrees

Pedigrees are family trees used to track how a trait passes through generations. They help scientists and students see whether a trait is dominant or recessive, whether it is autosomal or sex-linked, what genotypes family members may have, and what phenotypes may appear in future generations. For families with a history of inherited disease, this information can be important for family planning. In plants and animals, inheritance is often studied with crosses. Monohybrid crosses can show...

multiple allele traits

Blood Type and Allele Interactions

Multiple alleles can shape traits through blood type, sickle cell anemia, incomplete dominance, and codominance. Multiple allelism means a gene has three or more allelic forms. Diploid organisms, including humans, usually carry only two alleles for each gene, but many human genes exist in multiple forms in the population. Human blood type is a clear example of multiple allelism. The blood type gene has three alleles: I A , I B , and i. These alleles help determine which blood type a person has...

Epistasis describes how one gene can mask or change the effect of another gene. In high school genetics, this helps explain why many traits do not follow a simple single-gene pattern. Instead, alleles at different locations can work together to shape the final phenotype. Mendel studied seven unrelated pea traits, but most traits involve multiple gene interactions. Epistasis often happens when one gene interferes with the expression of another gene. It can also occur when genes are part of the...

polygenic traits

Polygenic Traits in Human Height

Polygenic traits are traits controlled by more than one gene. Human height is a clear example of this kind of inheritance. Because many genes work together, the final trait can vary a lot from person to person. Researchers have found hundreds of loci, or gene locations, that influence height. There are likely many more that have not yet been identified. Many of these genes affect cartilage in the growth plates of the long bones in the arms and legs, either directly or indirectly. Height is...

pleiotropy

SOX10 and Multiple Traits in Pleiotropy

Pleiotropy is when one gene affects more than one trait. The SOX10 gene is a clear example because it can influence pigmentation, hearing, and intestinal movement. These traits may seem unrelated, but they can all be linked to the same gene change. In humans, a deleted region in SOX10 can cause Waardenburg Syndrome Type 4, or WS4. WS4 is an autosomal recessive disorder, which means a person usually inherits two altered copies of the gene. Common signs include a white forelock,...

nature and nurture

Genes and Environment Shape Height

Genes and environment both shape human height and other traits. Genes are the inherited instructions we get from our parents. Environment includes factors such as diet, stress, and social conditions. Many phenotypes, or observable traits, reflect both influences. Some also show up later in life, including cancer and other diseases. Height is a clear example of this interaction. Scientists estimate that 70-90% of height variation comes from genetic differences among people. The remaining 10-30%...

chromosomal theory of inheritance

How Genes Map to Chromosomes

Genes map to chromosomes, and this idea explains how Mendel’s inheritance patterns work. Gregor Mendel published his pea plant breeding results in 1866. He showed that physical traits follow predictable patterns. At the time, scientists did not yet know that genes existed. Mendel used the word "factors" for the hereditary units he studied. The details behind Mendel’s laws of segregation and independent assortment were still unknown for many years. In the late 1800s, better microscopes and...

non-nuclear inheritance

Maternal DNA in Mitochondria and Chloroplasts

Maternal DNA in mitochondria and chloroplasts explains how some genes are inherited outside the nucleus. Most DNA is in the nucleus, but mitochondria and chloroplasts in the cell cytoplasm also carry their own DNA and can copy it independently of nuclear DNA. Mitochondria are found in both plant and animal cells. They are called the powerhouses of eukaryotic cells because they break down glucose to make energy for cellular activity. Mitochondrial DNA has about 37 genes, and many help with...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance explains how traits on the X chromosome are passed through families. In most mammalian species, females have two X sex chromosomes, while males have one X and one Y. A mutation on one X chromosome may be masked in females by a normal allele on the other X. In males, that same mutation is more likely to show because there is no second normal X to balance it. Traits caused by changes on the X chromosome are called X-linked traits. Color blindness is a well-studied example.

sex-linked disorders

X- and Y-Linked Disorder Patterns

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked. Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome...

x-inactivation

Barr Bodies and X-Chromosome Balance

Barr bodies and X-chromosome balance help explain how female mammalian cells control gene activity from the X chromosome. The human X chromosome carries far more genes than the Y chromosome. Because males usually have one X chromosome and females have two, females would make twice as many of some proteins without a control system. To prevent that imbalance, female mammalian cells inactivate nearly all the genes on one X chromosome during early embryonic development. The inactive X condenses...

key terms and concepts

Explore epistasis through rabbit coat color, where TYR can mask TYRP1 and change fur from black or brown to white in recessive epistasis.

Gene Masking in Rabbit Fur Color | JoVE K12

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Next Generation Science Standards

High School

Life Science

HS-LS3-1

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

Chi-square Analysis

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Pedigree Analysis

Probability Laws

Overview

The probability of inheriting a trait can be calculated using the sum and product rules. The sum rule is used to calculate the probability of ...

11. Use probability and statistical models to explain the variation of expressed traits within a population. Examples: pedigree charts, family and population studies

9-12.B.3.11

Punnett Squares

Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
Some of Mendel&#8217;s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A ...

Law of Independent Assortment

Multiple Allele Traits

Incomplete Dominance

Gregor Mendel&#39;s work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid ...

Lethal Alleles

Agouti: A Lethal Allele
Lucien Cu&#233;not discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is ...

Polygenic Traits

background-and-environment-affect-phenotype

Background and Environment Affect Phenotype

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X and Y Chromosomes

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The Y Chromosome Determines Maleness

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The Ratio of X Chromosome to Autosomes

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X-linked Traits

Sex Linked Disorders

Dosage Compensation

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X-inactivation

Blood Types

Human blood is classified into different types based on the presence of antigens on the red blood cell&#39;s surface and antibodies in the plasma. Proper ...

Blood Transfusion and Agglutination

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a. Use mathematics and computational thinking to predict patterns of inheritance, including dominance, recessiveness, codominance, and incomplete dominance. Examples: Use a Punnett square to illustrate codominance in genes for blood types. Use probability rules to predict the phenotypes of offspring from different parental combinations.

9-12.B.3.11.a

When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have uncovered ...

Pleiotropy

Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene cause ...

Nature and Nurture

Many human characteristics, like height, are shaped by both nature&mdash;in other words, by our genes&mdash;and by nurture, or our environment. For ...

b. Obtain, evaluate, and communicate information about how the interplay of heritable risk factors, somatic mutations, and environment influences human disease. Examples: Because heart disease has heritable and environmental risk factors, a person's total risk needs to include both factors. Cancers have both heritable (breast, lung, colorectal, skin, cervical cancer) and environmental risk factors (smoking, diet, sun exposure, HPV exposure). Clarification: Epigenetics could be an extension of this standard.

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Oogenesis

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What is Meiosis?

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Meiosis I

Meiosis II

Meiosis vs. Mitosis

Crossing Over

Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to ...

Nondisjunction

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Karyotyping

12. Develop and use an evidence-based model to illustrate the formation of reproductive cells through the process of meiosis. Example: Use karyotype cutouts to illustrate independent assortment into reproductive cells.

9-12.B.3.12

Homologous Recombination

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Gene Conversion

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Overview of Transposition and Recombination

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conservative-site-specific-recombination-and-phase-variation

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic ...

a. Construct an explanation of how new genetic combinations and variations occur during crossover.

9-12.B.3.12.a

Organization of Genes

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

Teratogenicity

The ability of a drug to produce structural deformations and functional abnormalities in the developing embryo or the fetus is called teratogenicity, and ...

Mutagenicity and Carcinogenicity

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An Overview of Genetic Analysis

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Genetic Crosses

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Genetic Screens

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b. Obtain, evaluate, and communicate information about how errors during meiosis and environmental factors affect the expression of traits. Examples: Translocation between chromosomes 8 and 11 can cause myeloproliferative disorder and lymphoma. Smoking and exposure to teratogenic chemicals can alter genes in reproductive cells that can be passed on to offspring.

9-12.B.3.12.b

Gene Masking in Rabbit Fur Color

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