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Luck of the sperm? Determining your babies characteristics!

I am not suggesting that everyone has gone and had an affair and has produced a baby as a fruit of that naughtiness, (however if you have you might not want to show this to your other half!) but have you ever wondered why if you both have brown eyes your child has blue, or why if your blonde haired you end up with a red hair child?

Well a few of us (namely Him up north, Mummy central and Carol finds her wings) had a very bizarre conversation last night that started off about genetics and finished with sperm wars! As Him up North said and I quote ‘Only on Twitter could you have discussions on monkey dolls and sperm. And get away with it.’ And it is true!

So I bring to you a little genetics lesson! This is looking at inherited characteristics which include hair and eye colour, freckles, tongue rolling, facial features and some genetic diseases.

Step 1


In order to determine your characteristic be it brown eyes or blonde hair you have two genes (or alleles) that code for them. One is inherited by the mother and one is inherited by the father!


Step 2


What determines the coding is how dominant those genes are. If you are given a brown eyed gene from the mother (B) and a brown eyed gene for the father (B) you will of course be brown eyed (BB). But what if you are given a blue eyed gene (b)from the father? You get this Bb. You are still however brown eyed. 


This is because brown is always dominant over blue (blue is what we call the recessive gene) and therefore brown will dominate every time!


The only way you will get a blue eyed child is if the Mother is a carrier of the blue eyed gene (b)! Two recessive alleles with produce that characteristic! (bb = blues eyes)


I hoping I am making sense so far! (It is so much trickier without PowerPoint!)


Some diagrams to help!



B = Brown eyes (dominant)

b = blue eyes (recessive)

Top green is Mum = B (From her mum) and B (From her dad) = Mum is Brown eyed

Side green is Dad =  b (From his Mum) and b (From his Dad) = Dad is Blue eyed

The children (or offspring if you want me to be scientific!!!) are therefore the boxes in yellow! All end up with a dominant B gene so all children will be brown eyed!

However if this were to happen!



Again:

B = Brown eyes (dominant)

b = blue eyes (recessive)

Mum in this case has one B (brown gene) and one b (blue gene) She is still brown because brown is dominant!

Dad still has the two blue eyes genes!

The yellow offspring as you can see, 2 have the dominant B gene so will be brown eyed and two have the recessive b gene so will be blue eyed. It now is a 50/50 chance!

Last one!



In this case both parents are brown eyed as they both have the dominant brown eyed gene but but hey both carry the recessive blue eyed gene! As you can see fro the grid, one offspring is totally dominant brown eyed BB (25% chance) Two are dominant but carry the brown eyed gene (50%) and only one had two blue genes! Only a 25% chance you will have blue eyed children!

However at this point it is in fact all luck of the sperm (and egg!!) as to what genes they possess and which one makes the journey to determine your childs characteristics!

I have two blue eyed children and one brown and both my husband and I are brown eyed! This means we must both carry the blue eyed gene!

The only time you can really question what is going on is if both parents are blue eyed and the children are brown? He he!

 

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22 comments to Luck of the sperm? Determining your babies characteristics!

  • carolefindsherwings

    Hehe – you know, now you've done those diagrams I get a vague memory of GCSE biology and colouring in pictures of eyes…

    Clearly me and OH both have recessive blonde-and-curly genes hidden away somewhere!

  • Anonymous

    Kerry

    So as to not to panic some people out there who may be blue eyed but have a brown eyed baby (who may be reading this and wondering if their wife did indeed have an affair!) I would just like to add a few things.

    Firstly, although classroom genetics hold mostly true, inheritance of eye colour is much more complicated than this as it is a polygenetic trait. This means it involves many different genes; some of which remain unknown to us still. There is also the issue that during recombination the parents genes for eye colour could be modified.
    Differences in eye colour and shades are due to varying ratios of (pigments) eumelanin produced by melanocytes in the iris. Blue eyed people have very little melanin where as brown eyed contain a lot. It is true however that brown is the most dominant eye colour in humans.

    However, it is also true that due to the complex way in which eye colour is inherited it is entirely possible for two blue eyed parents to give birth to a brown eyed child! So don't panic xx

    Sam (Also twin mummy and science teacher)

  • Vickie Ford

    Haha, I take it is the same for hair then!

  • multiplemummy

    Anonymous (sam),

    Thank you!

    I never meant to scare anyone, it was only a bit of fun and indeed my terrible sense of humour!

    As far as the science goes, I don't pretend to know more than classroom science, I trained as an OT and qualified as a teacher later. Your knowledge is far superior than mine. But you learn something knew everyday so thanks.

  • Him Up North

    I think anonymous just trots that excuse out because her hubby might be reading… ;-)

    Great piece. Very informative. x

  • Sam B

    Kerry

    My knowledge is not that great either – I trained in environmental science – but over the years of teaching I have been asked questions by students that caused me to go away and do a bit more reading up on subjects! I sincerely hope you don't think I was undermining you – I think that you explained it really well – I can tell you are a great teacher!
    Keep up the great work – I love reading your blog! xxx

    Sam B x

  • multiplemummy

    Sam,

    Thank you, that has made me feel better, I was worried you thought me stupid! I had only been teaching 2 years before babies and then 3 under 3 has meant I cannot go back for the time being so I have been out of the classroom for a while! You are right I do need to do more reading, as kids ask all sorts of questions! Thank you for reading and glad you enjoy it. It is my escape! xx

  • Mummy's Little Monkey

    I find this topic really interesting, actually – thanks to you, and to Sam, for shedding some light.

    I always thought your kids either had Mum or Dad's eye colour – but my two kids totally blew that theory out of the water!

    My OH has Hazel eyes, and mine are Green. But our eldest daughter has dark brown eyes, and our youngest has bright blue!!!!

    Yes, they're both his kids, I promise!! ;) x

  • Sam B

    Kerry

    It was only because I had to teach A level biology (which involved me reading and learning topics the week before I taught the students!). I still tremble at the thought of teaching certain GCSE physics topics!! I NEVER thought you stupid – I would say you were one of the most insightful, intelligent and articulate people I know…plus you are very kind and thoughtful.

    Take care, Sam x

  • HELEN

    It's a very interesting subject, I remember learning about it at school with interest – Big b's & Little b's. my OH has dark brown eyes, I have blue, my son has Hazel eyes, my daughter has one dark Brown & one Hazel (a pigment thing?)and my 2nd son has blue eyes, I'm pretty sure both my OH's parents have brown eyes, (they're def. not blue) so I was surprised when I got my little blue eyed boy…..science is a mysterious thing which I no nothing about!!
    x

  • multiplemummy

    Helen,

    The only thing I can think is your OH must carry the blue eye gene so either both or one of his parents must have been carriers of the blue eye gene and given him one! Matched with you blue eyes makes a blue eye child! The hazel must be a pigment thing.I don't know it that indepth …let me call in my friend Sam!

    SAM!!!! Where are you? What do you think? x

  • HELEN

    ha ha, yes Sam, where are you when we need you!!
    I will have to do some investigating into my OH's family history, after having the 1st 2 I assumed that there were no little b's in his family but alas there must be one & I finally get a child of mine that resembles me, even if it is only by eye colour!!
    x

  • Donna@MummyCentral

    Just had a chance to sit down with a coffee and read your blog. It's really interesting – and as I was a science dunce at school, I didn't know a lot of it. Always thought a child with two brown-eyed parents HAD to be brown-eyed (or mum's been naughty!) And the same with blue eyes. But genetics really are fascinating. Have read about parents who have one dark-skinned, dark-haired child, and a blonde blue-eyed child.
    Glad that what seemed a bit of a daft conversation on Twitter has brought to light a lot of interesting information!
    Sperm Wars by Robin Baker is a fascinating read – I had to review it MANY years ago, and my hubby found it really interesting too.
    Thankfully my kids are both the spitting image of their Dad, so I'm safe (although they look nothing like me – maybe they're not mine LOL!!!!)

  • Sam B

    Kerry and Helen

    It is very simple for brown eyed parents to produce a blue eyed child as well as a blue and brown eyed couple producing a brown eyed child. You explained this very well in your blog Kerry!

    Eye colour is a continuous spectrum determined by the ratio of pigments and the amount of melanin produced.

    Hazel eyes have more melanin than blue eyed people but less than brown. As to why they seem to change colour… Well eye colour is very subjective and can be affected by the light conditions and sources you are viewing in. Hazel eyes like any light coloured eye also reflects colours around them (may explain why they seem to change?)

    Nobody really knows how Hazel eyes come about (ie how they seem to change) and much research has been undertaken, but so far we have only come up with models and theories.

    Sorry I can't help on this one!

    Sam x

  • Elizabeth aka Mommatwo

    I think this is fascinating – I have blue eyes, as do both my parents, my husband's are brown but neither of his parents have brown eyes – his Dad's are blue and his Mum's are green – his to sisters both have brown eyes too. I can never work it out.
    Our older son has brown eyes with green centres so I've assumed that brown and green are the same gene at different ends of the pigment scale so could be totally wrong.
    Baby still has baby coloured eyes but it will be interesting to see if his are different.

  • The Real Supermum Blog

    They were not monkey babies ha they were reborn dolls – please dom't get me started on them again they gave me nightmares.

    For example if both parents have brown eyes there will be a 75% chance baby will have brown too, 18.75% they will have green, 6.25% chance they will have blue.

    It is really quite fascinating, but there really is no way of guessing what eye colour or what hair colour your baby will have. I remember the story about the white couple who gave birth to a black baby. Yes it was both their child. But I can understand if that father in question ever doubted if the baby was his.

  • multiplemummy

    You are right you can never know..it is all just probability – Luck of the sperm as I said (and egg!) as to what it codes for. Each sperm and egg will be different!

  • Mummy and the Beastie

    I was fascinated by this subject when I was pregnant and interesting about 2 brown eyes having a blue eyed baby, I didn't think that was possible. I have blue eyes and my husband brown (half turkish) and I was convinced my boy would have brown eyes but he has blue. So my husband carries the blue gene! x

  • Donna@MummyCentral

    Just had a chance to sit down with a coffee and read your blog. It's really interesting – and as I was a science dunce at school, I didn't know a lot of it. Always thought a child with two brown-eyed parents HAD to be brown-eyed (or mum's been naughty!) And the same with blue eyes. But genetics really are fascinating. Have read about parents who have one dark-skinned, dark-haired child, and a blonde blue-eyed child.
    Glad that what seemed a bit of a daft conversation on Twitter has brought to light a lot of interesting information!
    Sperm Wars by Robin Baker is a fascinating read – I had to review it MANY years ago, and my hubby found it really interesting too.
    Thankfully my kids are both the spitting image of their Dad, so I'm safe (although they look nothing like me – maybe they're not mine LOL!!!!)

  • multiplemummy

    Sam,

    Thank you, that has made me feel better, I was worried you thought me stupid! I had only been teaching 2 years before babies and then 3 under 3 has meant I cannot go back for the time being so I have been out of the classroom for a while! You are right I do need to do more reading, as kids ask all sorts of questions! Thank you for reading and glad you enjoy it. It is my escape! xx

  • [...] of genetics and how eye colour is determined. If you want to find out more about this read my Luck of the Sperm post! It reveals all and show you how clever it all [...]

  • my siblings and parents have brown eyes except 1 sister (I do think she is the coal mans lol) my husband is blue eyes all my girls have blue eyes and both my boys have hazel eyes I must be a blue gene carrier.

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