What Is The Genotype For Green Eyes?

What Is The Genotype For Green Eyes
Why are our kids’ eyes different colours? – Let’s look at why a blue-eyed parent (dad) and a brown-eyed parent (mum) and can have brown, green, and blue-eyed children. For gene 1, OCA2, there are two possibilities: brown or blue. The brown version of gene 1 is dominant over the blue one. Dominant means that if at least 1 of your two copies is brown (Bb), then you will have brown eyes. Geneticists represent the different versions of the eye colour gene as B for brown and b for blue (the capital letter is the dominant, the lowercase, recessive).

  • So brown eyes are either Bb or BB and blue eyes are bb.
  • For gene 2, there are two possibilities, green or blue.
  • Green is dominant over blue.
  • Green eyes can be GG, or Gb, while blue eyes are bb.
  • Brown is dominant over green, so if you have a B version of gene 1 and a G version of gene 2, you will have brown eyes.

The possible gene combinations that can give you brown, green, or blue eyes are shown in the chart. Back to the green or blue-eyed children. Dad can only be bb bb as he has blue eyes. Since mum has brown eyes, she could have any of six different possibilities.

Is there a gene for green eyes?

Eye color comes from genes that make melanin – Brown, green and blue eye color comes from a pigment called melanin, Brown eyes have a lot of melanin in the iris, green eyes have a medium amount, and blue eyes have little or no pigment. Two genes, BEY2 and GEY, work together to make brown, green, or blue eyes.

  1. Each gene comes in two versions or alleles,
  2. One form of BEY2 makes lots of melanin (and is usually referred to as B ) while the other form makes only a little ( b ).
  3. One form of GEY makes some melanin ( G ) while the other makes only a little ( b ).
  4. So how do you get eye color from all of this? If you have B you get brown eyes, G (but no B) you get green eyes and if you only have b, then you get blue eyes.

Most likely, hazel eyes simply have more melanin than green eyes but less than brown eyes. There are lots of ways to get this level of melanin genetically. It may be that hazel eyes are the result of genes different from GEY and BEY2, Something like HEY for hazel.

And maybe HEY is a bit like BEY2 and GEY in that it comes in two forms – one that makes enough melanin for hazel eyes ( H ) and one that makes little or no melanin ( b ). If this were true, the scheme for eye color would have to be changed. In the new scheme, you would have brown eyes if you had B, hazel eyes if you had H but not B, green eyes if you had G but not H or B and blue eyes if you only had b,

My gut tells me this probably isn’t the answer. Even though this sounds pretty complex, it seems like it wouldn’t be that much harder to tease out than green and brown eyes. We still do not completely understand the genetics of eye color, particularly when it comes to less common colors, like hazel.

(Image via Shutterstock) Another possibility is a variation on this theme. Maybe hazel eyes come from different versions of BEY2 or GEY, I said at the outset that there were two versions of each gene. But what if there were more? What if there were many versions that result in the various shades of color we see? This is certainly plausible and some recent research suggests that this might be part of the story.

But again, we don’t know. I would think the genetics again would be easy enough that it would have been figured out by now. Another possibility is that there may be modifier genes. These are genes that would affect how much melanin BEY2 or GEY make. For example, you could get a gene that has GEY make more melanin or BEY2 make less.

What are genotypes for eye color?

Genotypes In one sense, the term ” genotype “—like the term “genome”—refers to the entire set of genes in the cells of an organism. In a narrower sense, however, it can refer to different alleles, or variant forms of a gene, for particular traits, or characteristics. An organism’s genotype is in contrast with its phenotype, which is the individual’s observable characteristics, resulting from interactions between the genotype and the environment. There is a complex connection between the genotype and the phenotype. Since the phenotype is the result of an interaction between genes and the environment, different environments can lead to different traits in individuals with a particular genotype. In addition, different genotypes can lead to the same phenotype. This happens because genes have different alleles. For some genes and traits, certain alleles are dominant while others are recessive, A dominant trait is one that shows up in an individual, even if the individual has only one allele”>allele that produces the trait. Some aspects of eye color work this way. Brown eyes, for instance, are dominant over blue eyes. This is because a pigment called melanin produces the brown color, while having no pigment leads to blue eyes. Having just one allele for the dark pigment is enough to make your eyes brown. There actually are several different pigments that affect eye color, each pigment resulting from a particular gene. This is the reason why people can have green eyes, hazel eyes, or any of a range of eye colors apart from blue or brown. When discussing genotype, biologists use uppercase letters to stand for dominant alleles and lowercase letters to stand for recessive alleles. With eye color, for instance, “B” stands for a brown allele and “b” stands for a blue allele. An organism with two dominant alleles for a trait is said to have a homozygous dominant genotype. Using the eye color example, this genotype is written BB. An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb. Finally, the genotype of an organism with two recessive alleles is called homozygous recessive. In the eye color example, this genotype is written bb. Of these three genotypes, only bb, the homozygous recessive genotype, will produce a phenotype of blue eyes. The heterozygous genotype and the homozygous dominant genotype both will produce brown eyes, though only the heterozygous genotype can pass on the gene for blue eyes. The homozygous dominant, homozygous recessive, and heterozygous genotypes only account for some genes and some traits. Most traits actually are more complex, because many genes have more than two alleles, and many alleles interact in complex ways. : Genotypes

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What genotype is hazel eyes?

The Genetics of Eye Color The genetics of blood type is a relatively simple case of one locus Mendelian genetics—albeit with three alleles segregating instead of the usual two (). Eye color is more complicated because there’s more than one locus that contributes to the color of your eyes.

In this posting I’ll describe the basic genetics of eye color based on two different loci. This is a standard explanation of but, as we’ll see later on, it doesn’t explain the whole story. Let’s just think of it as a convenient way to introduce the concept of independent segregation at two loci. Variation in eye color is only significant in people of European descent.

At one locus (site=gene) there are two different alleles segregating: the B allele confers brown eye color and the recessive b allele gives rise to blue eye color. At the other locus (gene) there are also two alleles: G for green or hazel eyes and g for lighter colored eyes.

The B allele will always make brown eyes regardless of what allele is present at the other locus. In other words, B is dominant over G, In order to have true blue eyes your genotype must be bbgg, If you are homozygous for the B alleles, your eyes will be darker than if you are heterozygous and if you are homozygous for the G allele, in the absence of B, then your eyes will be darker (more hazel) that if you have one one G allele.

How is Eye Colour Inherited (Bb) – GCSE Biology (9-1) | kayscience.com

Here’s the Punnett Square matrix for a cross between two parents who are heterozygous at both alleles. This covers all the possibilities. In two-factor crosses we need to distinguish between the alleles at each locus so I’ve inserted a backslash (/) between the two genes to make the distinction clear.

  1. The alleles at each locus are on separate chromosomes so they segregate independently.
  2. As with the ABO blood groups, the possibilities along the left-hand side and at the top represent the genotypes of sperm and eggs.
  3. Each of these gamete cells will carry a single copy of the Bb alleles on one chromosome and a single copy of the Gg alleles on another chromosome.

Since there are four possible genotypes at each locus, there are sixteen possible combinations of alleles at the two loci combined. All possibilities are equally probable. The tricky part is determining the phenotype (eye color) for each of the possibilities.

According to the standard explanation, the BBGG genotype will usually result in very dark brown eyes and the bbgg genotype will usually result in very blue-gray eyes. See the examples in the eye chart at the lower-right and upper-left respectively. The combination bbGG will give rise to very green/hazel eyes.

The exact color can vary so that sometimes bbGG individuals may have brown eyes and sometimes their eyes may look quite blue. (Again, this is according to the simple two-factor model.) The relationship between genotype and phenotype is called penetrance,

If the genotype always predicts the exact phenotpye then the penetrance is high. In the case of eye color we see incomplete penetrance because eye color can vary considerably for a given genotype. There are two main causes of incomplete penetrance; genetic and environmental. Both of them are playing a role in eye color.

There are other genes that influence the phenotype and the final color also depends on the environment. (Eye color can change during your lifetime.) One of the most puzzling aspects of eye color genetics is accounting for the birth of brown-eyed children to blue-eyed parents.

This is a real phenomenon and not just a case of mistaken fatherhood. Based on the simple two-factor model, we can guess that the parents in this case are probably bbGg with a shift toward the lighter side of a light hazel eye color. The child is bbGG where the presence of two G alleles will confer a brown eye color under some circumstances.

* If the two genes were on the same chromosome this assumption might be invalid because the two alleles on the same chromosome (e.g., B + g) would tend to segregate together. Linked genes don’t obey Mendel’s Laws and this is called linkage disequilibrium,

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How many different genotypes result in green eyes?

For gene 2, there are two possibilities, green or blue. Green is dominant over blue and so G usually represents green and b, blue. Green eyes, then, can be GG or Gb while blue eyes are bb. A two-gene model for eye color.

BB bb Brown
bb GG Green
bb Gb Green
bb bb Blue

What is genotype AA for eyes?

The genotype AA indicates a high chance of brown eyes with severely decreased chances of green eyes and almost no chance of blue eyes. Genotype AG has more similar chances of having green or brown eyes but still a drastically smaller chance of having blue eyes.

What makes green eyes?

Green Eyes – Only about 2 percent of the world’s population has green eyes. Green eyes are a genetic mutation that produces low levels of melanin, but more than blue eyes. As in blue eyes, there is no green pigment. Instead, because of the lack of melanin in the iris, more light scatters out, which make the eyes appear green.

Which eye color is dominant?

The Genetics of Eye Color Download the PDF version of Biotech Basics: Genetics of Eye Color Countless students have been taught that a single gene controls eye color, with the allele for brown eyes being dominant over blue. Scientists now realize such a model is overly simplistic and incorrect. What you need to know:

DNA provides the set of recipes, or genes, used by cells to carry out daily functions and interact with the environment. Eye color was traditionally described as a single gene trait, with brown eyes being dominant over blue eyes. Today, scientists have discovered that at least eight genes influence the final color of eyes. The genes control the amount of melanin inside specialized cells of the iris. One gene, OCA2, controls nearly three-fourths of the blue-brown color spectrum. However, other genes can override the OCA2 instruction, albeit rarely. This multifactorial model for eye color explains most of the genetic factors that influence eye color.

Introduction In 1907, Charles and Gertrude Davenport developed a model for the genetics of eye color. They suggested that brown eye color is always dominant over blue eye color. This would mean that two blue-eyed parents would always produce blue-eyed children, never ones with brown eyes.

For most of the past 100 years, this version of eye color genetics has been taught in classrooms around the world. It’s one of the few genetic concepts that adults often recall from their high school or college biology classes. Unfortunately, this model is overly simplistic and incorrect – eye color is actually controlled by several genes.

Additionally, many of the genes involved in eye color also influence skin and hair tones. In this edition of Biotech Basics, we’ll explore the science behind pigmentation and discuss the genetics of eye color. In a future edition, we’ll discuss genetic factors that contribute to skin and hair color.

A primer on pigmentation The color of human eyes, skin and hair is primarily controlled by the amount and type of a pigment called melanin. Specialized cells known as melanocytes produce the melanin, storing it in intracellular compartments known as melanosomes. The overall number of melanocytes is roughly equivalent for all people, however the level of melanin inside each melanosome and the number of melanosomes inside a melanocyte varies.

The total amount of melanin is what determines the range of hair, eye and skin colors. There are a number of genes involved in the production, processing and transport of melanin. Some genes play major roles while others contribute only slightly. To date, scientists have identified over 150 different genes that influence skin, hair and eye pigmentation (an updated list is available at ).

  1. A number of these genes have been identified from studying genetic disorders in humans.
  2. Others were discovered through comparative genomic studies of coat color in mice and pigmentation patterns in fish.
  3. A previous Biotech101 article that provides an overview of comparative genomics can be found,) figure one Eye color genes In humans, eye color is determined by the amount of light that reflects off the iris, a muscular structure that controls how much light enters the eye.

The range in eye color, from blue to hazel to brown (see figure one), depends on the level of melanin pigment stored in the melanosome “packets” in the melanocytes of the iris. Blue eyes contain minimal amounts of pigment within a small number of melanosomes. Irises from green–hazel eyes show moderate pigment levels and melanosome number, while brown eyes are the result of high melanin levels stored across many melanosomes (see figure two, left).

To date, eight genes have been identified which impact eye color. The OCA2 gene, located on chromosome 15, appears to play a major role in controlling the brown/blue color spectrum. OCA2 produces a protein called P-protein that is involved in the formation and processing of melanin. Individuals with OCA2 mutations that prevent P-protein from being produced are born with a form of albinism.

These individuals have very light colored hair, eyes and skin. Non-disease-causing OCA2 variants (alleles) have also been identified. These alleles alter P-protein levels by controlling the amount of OCA2 RNA that is generated. The allele that results in high levels of P-protein is linked to brown eyes.

  1. Another allele, associated with blue eye color, dramatically reduces the P-protein concentration.
  2. On the surface, this sounds like the dominant/recessive eye color model that has been taught in biology classes for decades.
  3. However, while about three-fourths of eye color variation can be explained by genetic changes in and around this gene, OCA2 is not the only influence on color.
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A recent study that compared eye color to OCA2 status showed that 62 percent of individuals with two copies of the blue-eyed OCA2 allele, as well as 7.5 percent of the individuals who had the brown-eyed OCA2 alleles, had blue eyes. A number of other genes (such as TYRP1, ASIP and ALC42A5 ) also function in the melanin pathway and shift the total amount of melanin present in the iris.

  1. The combined efforts of these genes may boost melanin levels to produce hazel or brown eyes, or reduce total melanin resulting in blue eyes.
  2. This explains how two parents with blue eyes can have green- or brown-eyed children (an impossible situation under the Davenport single gene model) – the combination of color alleles received by the child resulted in a greater amount of melanin than either parent individually possessed.

As a side note, while there is a wide variability in eye color, colors other than brown only exist among individuals of European descent. African and Asian populations are typically brown-eyed. In 2008 a team of researchers studying the OCA2 gene published results demonstrating that the allele associated with blue eyes occurred only within the last 6,000 – 10,000 years within the European population.

Pigmentation research at HudsonAlpha Dr. Greg Barsh, a physician-scientist who has recently joined the HudsonAlpha faculty, and his lab study key aspects of cell signaling and natural variation as a means to better understand, diagnose and treat human diseases. In particular, his work has focused on pigmentation disorders.

He has explored mutations that affect easily observable traits—such as variation in eye, hair or skin colors—as a signpost for more complex processes such as diabetes, obesity, neurodegeneration and melanoma, the most serious form of skin cancer. – Dr.

Where does the green eye gene come from?

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April 18, 2017 Spring is here, and the color green is popping up more and more everywhere you look. But you probably won’t be seeing too many green eyes. They’re actually very rare, and we thought we’d take a little time to give you all the info on why your friend with green eyes is pretty special. Out of brown, blue, and green, green eyes are the rarest in the world.

Only about 2% of the world’s population has green eyes. You might be surprised to learn that people with green eyes don’t actually have any green pigment in them. That’s because eye color is determined by the concentration of melanin and lipochrome in the iris.

  • Melanin is a brown pigment, and lipochrome is a somewhat yellowish pigment.
  • So for instance, people with brown eyes have a higher melanin concentration that makes their iris appear brown or almost black in some cases.
  • Blue eyes, in contrast, have very little melanin and lipochrome.
  • The blue color is caused by the scattering of light in the iris, also known as Rayleigh scattering.

This scattering only occurs when there is very little melanin in the eye, and it’s the same effect that causes us to see the sky as blue. People with green eyes have slightly more melanin and lipochrome in their eyes. Combined with the blue hue from the Rayleigh scattering and the yellowish tint from the lipochrome pigment, a green colored iris is produced.

Like we said before, only about 2% of the world’s population, or about 140 million people, have green eyes. And although they are sometimes confused with hazel eyes, the two are not the same. So where did our green-eyed ancestors come from? Most origins point to areas around the Caucasus Mountains, which link Asia and Europe.

That may help explain why so many different countries and continents have had green-eyed populations for thousands of years. There are passes in the Caucasus Mountains that were historically important trade and military routes. This constant movement could easily have helped spread the genes for green eyes to new territory over thousands of years.

So it turns out your friend with green eyes is pretty special after all. Although be sure to let them know that they don’t really have green eyes—just a combination of different pigments and light scattering. And because of that, changes in the light scattering can change the appearance of the iris, That’s why people with green eyes sometimes appear to have different shades of green irises.

Mood, weather, lighting, and even the colors they wear can have an effect on the appearance of their eyes. Whatever your eye color—green or blue, brown or hazel—you still need to have great vision to get the most out of your eyes. If you’ve been wearing contacts or glasses for years, then maybe it’s time to find out more about LASIK and getting the perfect vision you’ve always wanted.