Can someone accurately predict the eye color of a child before it is born using the mother and father’s eye color?
My gulp fiance and I were talking about what our children would look like (hair and eye color) and I just don’t understand how this works. I found a few places on the web that somewhat describe the possible outcomes, but it seems I’m even more confused now.
I have blue eyes, as do both my parents. She has brown eyes and so does both her parents. I’m not sure if it matters on how far back you need to go on the family tree, but most of my direct relatives have blue or green eyes. On her side all of her relatives have brown eyes.
Does race play a role in the changing the percentage? (I am Caucasian, she is Asian) I have heard from a friend that there has been cases where brown-eyed parents gave birth to a blue-eyed babies. (the eyes stayed blue, and no it wasn’t the postman)
We are not really hoping for a particular color (as long as HE likes football, I’ll settle for any color in the rainbow)
If anyone has a link or a formula we could play with, it would be much appreciated.
I successfully predicted (sort of) my grandmother’s eye color. My mother was adopted and she had never met her before.
Here’s how it worked for me.
My mother has brown eyes, brown is dominent.
My father had hazel eyes, hazel is recessive so he has 2 of them.
Me and my sister both have green eyes. Green eyes come from a recessive blue and recessive hazel gene. So my mother’s recessive gene had to be blue. We knew her mother was an Italian schoolteacher and she looked really local (Hawaiian) and so I presumed her father would have had 2 brown genes and her mother gave her blue. And lo she had blue eyes
So for you, you should have 2 blue genes, so guaranteed your child will have 1 blue gene. You wife has 1 dominent brown gene, and the other is unknown. So there’s a 50% chance your child will have brown eyes. The other half would give your child either green or blue.
I don’t know how black or grey eyes work. Probably black is also dominent so you wouldn’t have to think about that. To determine the other 50% you’d have to know the ratio of hazel, blue and grey eyes in your in-law’s ethnic background.
The process isn’t strict mendelian genetics, but for the sake of argument, we can treat it that way. The chances are greater than 90% that it will follow a mendelian genetic pattern.
jinxie’s assumptions are probably correct. You probably have two genes for blue, so any kid of yours will have blue eyes. Your wife could have two brown genes, or one brown and one blue. The fact that “everyone” in her family has brown eyes tips the odds a bit towards her having two brown genes, but it’s not a certainty. The blue gene can be passed down thru many generations without getting expressed.
If wifey has two brown genes, then the kids will have brown eyes, no matter your contribution.
If wifey has one brown, one blue, then it’s a 50-50 chance the kid will have blue eyes.
My grasp of statistics weakens tremendously when we add the second variable in like this (your wife, a fixed but unknown quantity, and I mean this in a good way). I’m sure someone on the board will be able to supply more mathematical rigor. But I think this means that there is less than a 25% chance of you having a blue-eye
(or non-brown) kid.
Odds look very good that you’ll have all brown eyed children.
Brown is dominant to both blue and green. Green is dominant to blue. Since you have blue eyes it’s easy to figure which genes you’re carrying: two copies of blue. We’d call that “bb.”
The question comes with your beloved’s eyes. She must have at least one gene for brown. From what you’ve told about her family and ethnic heritage, it sounds like she would have two genes for brown eyes. That would be “BB.”
Your children would get one eye color gene from you and one from her, making them “Bb.” Brown dominates. So their eyes would be brown.
Yes, ethnic background plays a role in this. The genes for blue and green eye colors seem to have originated in northern Europe. Your fiancee’s best chance of carrying a recessive eye color gene would be if she has a mixed heritage–say if she’s Filipino and someone in her family tree was Spanish. If that passed a blue eyed gene to her (a big if), then as Linear Crack says your children would have a 50% chance of getting either eye color.
You’re assuming there is a 50% chance his wife has both brown genes. But the chances are probably greater, since both her parents had brown eyes.
That said, the exact probability is meaningless to calculate - that is, in order to get a quantitative answer, you have to assign probabilities to facts. If we KNOW his wife has two brown-eye genes, the chances of the child having brown eyes is 100%. If we KNOW the wife has only one brown-eye gene, the odds are 50%. But the probability of her having two brown-eye genes is impossible to calculate, unless you know the genetic make-up of her parents, which we also don’t know exactly.
My mom has brown eyes. Her family has brown eyes. My dad has blue eyes, blond hair, and has as near as I can tell every “recessive” easily findable trait I have heard of. (hair, earlobes, skin tone…)
As do all three of their kids. (Well, the littlest one has red hair.)
My mother gets accused of being the nanny. By rights her looks should have beaten out my dad’s in some way if not all. But she has china blue eyed kids who scream even thinking about the sun looking back at her brown hair, chocolate eyes, and tan skin. Genetics are all well and good, but “recessives” don’t always recess exactly the way they “should”.
nope, i have brown eyes, but since i know i’m heterozygous i have a 50% off blue eyed kids with a blue eyed father, and a 25% with a brown eyed heterozygous father, and 0 chance with a brown eyed homozygous father.
your mom is heterozygous, that’s all.
Or “Chirish” as they say. Two of them have green eyes, all their siblings were dark-eyed. This is not because of dominant or recessive factors but is entirely attributable to that most decisive factor in evolution: mutation.
It seems most likely that any children will be dark-eyed but that’s not a guarantee. Both mothers of the aforementioned friends were mainland Chinese with nary a drop of European blood; dark-eyed all the way and no recessives.
For most people of European descent, light-eyes are a fairly common recessive. All that raiding and warring across borders produced quite the gene pool mix. This includes the group currently referred to as African-American. They also have European heritage and can produce light-eyed children.
Both of my parents have brown eyes but our background includes Welsh, Scottish, Irish, and Danish. Lots of opportunity for recessives genes to express themselves. Each of their four children has different hair and eye colour and we have varying degrees of sensitivity to sunlight. (There’s also some Cherokee in my genetic makeup.) Thus, I’m blonde, hazel-eyed and burn the second I step into direct sunlight and my sister is brunette, blue-eyed and can comfortably camp in Death Valley.
Ummm… I’m not sure why being male would affect whether a gene is dominant or recessive. Also, why would you have to do any explaining? Is she illiterate?
As for mutations: We are all mutants. We’d have to be in order to be individuals. Mutations are one of the driving forces of gene diversity and evolution. Some mutations are essentially neutral (e.g. eye colour), some are benign (e.g. developing air sacs that allow an animal to breathe outside of water) and some are deleterious (e.g. hyperactive cell replication leads to cancer.)
In some cases, a gene mutation that seems deleterious (in other words, nature selects against organisms with this gene) may turn out to be of benefit if the environment changes. Mutations can occur naturally (see quote below), through mis-copying during DNA replication, and through the organisms external environment (e.g. excess radiation.)
Quoting from my biology textbook:
"Members of a sexually reproducing population owe nearly all their genetic differences to the <b> unique </b> recombinations of existing alleles each individual receives from the gene pool. Of course, this allele variation has its ultimate basis in past mutations.
Sex shuffles alleles and deals them at random to determine individual genotypes. During meiosis, homologous chromosomes, one inherited from each parent, trade some of their genes by crossing over, and then the homologous chromosomes and the alleles they carry segregate randomly into separate gametes. Gamestes from one individual vary extensively in their genetic makeup, and each zygote made by a mating pair has a unique assortment of alleles resulting from the random union of a sperm and an ovum. A population, of course, contains a vast number of possible mating combinations, each bringing together the gametes of individuals that are likely to have different genetic backgrounds. Sexual reproduction recombines old alleles into fresh assortments every generation."
Note: New alleles originate only by mutation. Most mutations occur in somatic cells; these are generally not passed on to offspring. Mutations that occur in cell lines which produce the gamets generally can be passed on.
No, she is not illiterate. She can read and write in three languages. It’s just that when one person does the research for a question they both have, a period of “explaining” from the researcher to the non-reseacher soon follows.
Linear Indeed there can be mutants, but for the sake of argument we had to assume that you were strictly going with Mendelian genetics (if you ever took Biology Mendel was the monk who did all of the work with the sweet pea plants) which means that a dominant gene ALWAYS dominants and a recessice gene NEVER dominates.
in a simple punnentt square it would look like this: B___B_ She is homozygous with the brown eye gene
b Bb Bb
b Bb Bb
The “bb” is what you NEED to have to get blue eyes, because if there is a “B” in the cross it dominates. Thus if she is homozygous for brown eyes theoretically there is NO way that you can have anything but Brown eyed children. However if she is heterozygous (like your children would be) the it would look like this: B___b_ She is hetrozygous with the brown eye gene
b Bb bb
b Bb bb
So theoretically you would have a 50% chance of blue eyed children.
Unfortunately, human genetics don’t work out this neatly, but this gives you some idea.
Eye color isn’t a sex-linked gene. In other words it doesn’t reside on the Y chrosome. To go a further: since men are XY and women are XX if a gene resides on the X chromosome both sexes can inherit it, but if it resides on the Y chromosome, like Hemophilia, for example, only men can inherit it.
Hemophiia is an X-linked recessive. It is usually only expressed in males because they have no masking X chromosome. Females can express hemophilia but if both X chromosomes carry the recessive.
When I used to tutor biology the eye color example was usually the way kids caught on to classical genetics.
The sort of chart that explains this is hard to recreate in this format but I’ll try. “B” means a dominant gene for brown eyes and “b” means a recessive gene for blue eyes. Eye color has nothing to do with being male or female.
So, as a blue eyed person, you’re “bb.”
As a brown eyed person, your fiancee is either “BB” or “Bb.” There’s no way to tell for sure, but you can make a pretty good guess by checking her family history.
So here are the possibilities:
BB x bb
Bb Bb Bb Bb
[100% brown eyed children]
Bb x bb
Bb Bb bb bb
[statistically, 50% brown eyed children, 50% blue eyed]
Instances where two brown eyed parents produce a blue eyed children usually occur among people of European heritage, where brown eyed people often carry the recessive blue eye gene. That scenario works out like this:
Bb x Bb
BB Bb Bb bb
[statistically, 75% brown eyed children, 25% blue eyed]
Eye color mutations are rare enough to ignore, but a hidden recessive gene from intermarriage several generations back is a possibility worth considering.
