My Dear Sexy Readers,
Today, we are looking at something that my new mummy friends have been talking about very often. Why is my kid blond when we are all so dark?
The most amazing example of genetic inheritance was this Asian mummy friend who has the most beautiful blond hair blue-eyed daughter!
So how does this work exactly?
How does the genetics behind hair colour work?
Well genetics are not as simple as what we learnt at school. It's not just a matter of one dominant over one recessive gene. It's more like a combination of on/off activation of different genes! That is why there are so many different hair color. Also, as no science fact is set in stone and not much is known in exact details, there might be some regulation or influence of other different genes as well as accompanying compounds influencing them.
The colours
There are two types of melanin called Eumelanin and Pheomelanin:
*Eumelanin gives the black and brown colour,
-Black eumelanin, little of it causes grey hair whereas lots of it gives black hair.
-Brown eumelanin, little of eumelanin gives blond hair, lots of it gives dark brown hair.
*Pheomelanin gives a orange to yellow pigment which combined to the eumelanin level gives a reddish colour to the hair.
The amount we develop is influenced by the genes we inherit from both parents but several genes play a role in the final shade:
The genetics
Note: For basics in genetics, please feel free to check out SSS post over HERE
You inherit 23 chromosomes from your mum and 23 from your dad. We therefore get each gene
twice, which can be slightly different from mum to dad. Those alternatives of a gene are called alleles. So we
get 2 alleles for each gene.
The genes for hair colour are multiple, there is not just one! There are located on 2 different chromosomes 19 an 15. So in total we get genes from our parents that are just ON or OFF. In this case, there are not alleles OR can be alleles because they contain SNPs.
(SNPs or Single Nucleotide Polymorphisms are the most common types of genetic variations)
On the other hand and in addition to these, the Red hair gene is located on chromosome 16 and is a recessive gene passed down as an allele as the result of many SNPs.
As an example, let's imagine Dad is dark brown hair BBBBBBbb and mum has darkish blonde hair Bbbbbbbr. Baby could be anything between BBBBBBBr and will be darker than dad or bbbbbbbb and will be blonder than mum, could even be bbbbbbbr and have light strawberry hair. Also, I find that Light and Dark are very subjective concepts. For example I consider myself a brunette because I used to be much fairer, but people will mostly see me as blonde!
Note: The eye colour genes are located close to these and are usually inherited together in linkage ie people with blonde hair would usually have blue eyes. Key word here being Usually!
Final shade?
As many of us have noticed, our hair colour changes over time. We might be born with blond hair and turn out very dark later on. My son was born with dark brown hair, is now a young toddler with dark blond hair and will probably grow up to be a very handsome dark brown hair gentleman ;) Who knows?
The hair colour can also change depending on stress and hormonal levels.
Gene switches just get turned ON and OFF!
Aren't we all?
See you Soon for more Sexy Science,
References
http://www.madsci.org/posts/archives/2001-03/984769893.Ge.r.html
http://udel.edu/~mcdonald/mythredhair.html
http://www.nytimes.com/2008/11/11/science/11angi.html?_r=2&ref=science&oref=slogin&
http://www.myredhairgene.com/index.html
Wikipedia
