by Veronique Demers-Mathieu, Blogger

You can go see some definitions at the end if there is anything unclear 😉

Genes play a fundamental role in determining eyes, skin and hair color. Why do you have sensitivity/resistance to sunburn? (My sun loving skin versus that lobster skin that MC has inherited…)

Skin Color

The skin color (pigmentation) is due to the amount of melanin produced into the melanosomes who are responsible for the synthesis, storage and transport of melanin. There are two types of melanin:
Eumelanin, a brown/black pigment
Pheomelanin, a lighter pigment yellow/red

The environmental and genetic changes (loss/gain of genes or alleles) affect the production and the type of melanin.

A human with dark skin has eumelanin-rich pigmentation and sun-resistant alleles (MC1R locus) that protect again sunburn or redness (UV radiation or UVR conditions). More your eumelanin/pheomelanin ratio is elevated more you have protection against UVR.

You can increase the eumelanin level in your skin by eating foods rich in tyrosine (melanin is derived from tyrosine) and in vitamin A such as milk, eggs, cheeses, fish, carrots, tomatoes, red peppers and mangoes. For protecting your skin against sunburn and having a better tan, you can include vitamin C (foods as oranges, mangoes, kiwis and strawberries) and vitamin E (vegetable oils, nuts and sunflower seeds) in your diet. Vitamin C plays an important role in protecting skin cells. MC, our editor in chief should definitely start eating more of these beneficial foods for improving her tan 😉

A person with lightly pigmented skin (blond/red hair) has a lower eumelanin/pheomelanin ratio and a higher sensitivity to sunburn than human with dark skin.

 Ratio of eumelanin (brown/black pigment) /pheomelanin (yellow/red pigment) determines the skin color.

Hair

Like skin, hair and eye coloration are determined mainly by the concentration of melanin produced and stored in melanosomes.

  • Blond hair has been associated with a mutation of a TYRP1 gene (this gene controls tyrosinase-related protein1 (TYRP1) enzyme, which has a role in melanin synthesis) and KITLG gene (this gene influences the growth of melanosomes). The mutation of these genes causes a reduction of melanin production (You can consider me as a blond mutant ;))
  • Red hair has been related to the mutation of MC1R (melanocortin-1 receptor) gene (this gene induces low production of eumelanin-brown/black pigment and high production of pheomelanin).
  • Dark hair has many genes that contribute to this phenotype, but the specific genes are still unknown.

At least two gene pairs control human hair color:

  • A person with blond hair (Vero) has two recessive blond alleles“bb” (no brown allele).
  • A person with brown hair (MC and Jade) has either a dominant brown allele and a recessive blond allele (Bb) OR two brown alleles (BB). This is why two brown-haired parents with two “Bb” can have a blond-haired child (bb). The dominant allele (brown) masks the recessive allele (blond or red).
  • A person with red hair has two red-haired alleles (rr).

Eye Coloration

Just a little definition of eye shape : “Iris” is the colored and ring-shaped membrane behind the cornea of the eyes, with an adjustable circular pupil in the center.

Iris coloration in modern population is brown and varies from light to dark. Iris color phenotypes are determined (similarly as skin and hair) by the amounts of melanin and by the ratio of eumelanin/pheomelanin in the iris, which blue eyes have a lower ratio of eumelanin/pheomelanin than brown eyes.

Dark iris coloration may be more protection under the sun and high UVR than blue eyes because of the high level of eumelanin. If you have blue eyes and blond hair like me, you should be more careful with the exposition under the sun. 🙂

But what is the probability of getting our eye color?

Eye color is linked to dominant and recessive genes and therefore eye color can provide some basic clues about paternity. A person with one dominant and one recessive allele for a gene will have the dominant phenotype. So…

Brown is dominant over blue and green (Brown > Blue or Green) while green is dominant over blue (Green> Blue). Blue is always the recessive!


               

For exemple:

  • A person with blue eyes (Vero) has two recessive blue eye
    alleles (bb).
  • A person with brown eyes (Gen & Anna) can have one dominant brown eye allele and one recessive blue eye allele (Bb) OR brown eye allele and green eye allele (BG) OR two dominant brown eye alleles (BB).
  • A person with green eyes (MC) can have either two green eye allele (GG) OR one blue eye allele and one green eye allele (Gb)
  • If I am pregnant (blue eyes, bb) and my partner has blue eyes (bb),then my baby will have blue eyes with a 99% chance! (If not, I need to ask myself serious questions hahaha)
  • Again, if my partner has brown eyes (Bb), my baby will still have a 50% chance to get blue eyes. However, if he has brown eyes (BB), my kid has only a 25% chance to have blue eyes.
  • If my partner has green eyes (Gb), my baby has 50% change to possess blue eyes and 50% for green eyes.

We can determine the percentage of probability of child’s eye color by parents’ eye color (see below).

DEFINITIONS 101:

 

DNA or deoxyribonucleic acid is the hereditary material in humans. Half of our DNA comes from our mother and the other half is from our father. Our traits (such as eye and hair color) are passed on by genes in our DNA.

 Stop copying me!

 What do DNA helicase and perverts have in common? They both want to unzip your genes.

DNA

While the section of DNA is called a gene, a specific pattern in a gene is called an allele. For example, the gene would determine the hair color.

The specific pattern of the hair color gene that causes the hair to be black would be the allele. Some alleles are dominant or recessive. When an human carries one dominant and one recessive allele, the human will express the dominant phenotype (trait).

Allele

A gene is the basic physical and functional unit of heredity. Inside the DNA molecules are sections of information called genes. Each gene tells the cell how to make a specific protein which allow to define a trait such as an eye color.

Every child inherits two genes for each trait from their parents.

He said: I can’t help my behavior, it’s in my genes!

She said: I don’t care what’s in your jeans, stay out of mine.

What is the fastest way to determine the sex of a chromosome? Pull down its genes

Gene