Colour blindness query

NBLondon

There are multiple forms but the commonest is being unable to distinguish red/green. It's carried on the X chromosome - mother has XX, father has XY. In Artytarty's example, father has a faulty X but we assume mother has two good X. Any daughter will have one X from her mother and the bad X from her father; she will not have the symptoms because the good X from mother overrides the bad X from father - but she is a carrier because she now has a bad X which she could pass on to her sons in time. Any son will have a good X from his mother and the Y from his father so he won't be affected and nor will his offspring.

Any grandson from the daughter will have a 50% of inheriting the faulty X from carrier mother and thus be affected; any granddaughter from the daughter will have a 50% chance of inheriting the faulty X from carrier mother and thus being a carrier herself.

Which gives rise to what some people may consider odd - a boy cannot inherit colour-blindness from his colour-blind father - but he could inherit it from a colour-blind grandfather.

That's if mother has two good X; it is possible that Artytarty is a carrier and doesn't know it and if so there's a 50% chance that her daughter is a carrier too and has one faulty and one good X. In which case, hypothetical son has a 50% chance of inheriting the bad X and being colour-blind; hypothetical daughter has a 50% chance of getting bad X from mother and known bad X from father and being colour-blind and 50% chance of getting good X from mother and known bad X from father and being a carrier.

So there is then a chance that a sequence of grandmother, mother, daughter, granddaughter etc. are all carriers and don't know it because they have never had a colour-blind son but it gets less likely each generation....

silvercar

Which gives rise to what some people may consider odd - a boy cannot inherit colour-blindness from his colour-blind father - but he could inherit it from a colour-blind grandfather.

To add to my post above, my father was colour blind.

So either my boys inherited it from something from me that wasn't from him, or something from him that I carried.

I must say for all the abnormalities to inherit, this one would worry me least.

NBLondon

Well - the XY and red-green is just a simplification for the most common types... it could be that you have 2 dodgy X chromosomes; one of which came from your father and one from your mother (hence you are affected) and your sons got one each (hence different symptoms).

Ergates

silvercar wrote: »

To add to my post above, my father was colour blind.

So either my boys inherited it from something from me that wasn't from him, or something from him that I carried.

I must say for all the abnormalities to inherit, this one would worry me least.

Not neccessarily. Red/Green colourblindness is the most common form and that is the one "on" the sex chromasome (and hence all of the above).

But, you say you have no problems with red/green, which means you have one of the other sorts - which aren't on the sex chromasome and which affect men and women equally and which have different inheritance patterns.

The differences in your sons colour vision could just be down to how the gene has expressed rather than a difference in the gene.

GlasweJen

Ergates wrote: »

Not neccessarily. Red/Green colourblindness is the most common form and that is the one "on" the sex chromasome (and hence all of the above).

But, you say you have no problems with red/green, which means you have one of the other sorts - which aren't on the sex chromasome and which affect men and women equally and which have different inheritance patterns.

The differences in your sons colour vision could just be down to how the gene has expressed rather than a difference in the gene.

That's not quite true, what silvercar is describing is classic red-green colour-blindness.

Her red and green is different to your red and green but she's still able to distinguish them. When the colours mix it becomes difficult for her to work out the shades so brown is a nightmare and that's why red-green colour-blind people used to be excluded from "the trades".

kingfisherblue

silvercar wrote: »

To add to my post above, my father was colour blind.

So either my boys inherited it from something from me that wasn't from him, or something from him that I carried.

I must say for all the abnormalities to inherit, this one would worry me least.

It doesn't worry me, it's just something that I was curious about. My children have several other abnormalities between them , and some of those have caused many more difficulties in life. My other son, for example, was born with Down's Syndrome (which is not inherited - there is a strain that runs in families, but not the type that my son has). The same son was also born with several major abnormalities of the digestive system, requiring four operations when he was nine hours old. Colour blindness is mild in comparison, but possibly something that I understand less well.


Some interesting comments above, including those that are not about my situation. I don't ever remember knowing someone who was colourblind when I was younger - well, not that I was aware of anyway. I knew my father, but didn't know about his condition.

System

I'll be honest i didn't know it was herdiatary! My brother is colourblind, and my dad isn't so i assume its on my mums side, possibly my nans side as afaik my grandad wasn;t colourblind. Personally i'm not having kids but im wondering now if my sisters are carriers too? I take it if my brother has a son he too will have the same condition?

bouicca21

As Glaswejen points out people with red-green colour blindness see colours differently. We once had some beautiful pink flowers in the garden, which my ex insisted were blue. I think it was because the pink had a faint mauve tinge.

He used to get really annoyed at standard colour blindness tests - the sort where people like him saw one number whilst the rest of us saw a completely different one. He was quite sure there was either a conspiracy where everyone else was lying about the number or that there was some sort of trick and he'd see the 'right' number if only he could work out what the trick was.

NBLondon

xXMessedUpXx wrote: »

I'll be honest i didn't know it was herdiatary! My brother is colourblind, and my dad isn't so i assume its on my mums side, possibly my nans side as afaik my grandad wasn;t colourblind.

Correct. Nan might be a carrier who got it from a great-grandad then passed it to mum...

I take it if my brother has a son he too will have the same condition?

Not automatically - he can't inherit it directly from his father, it will depend on whether sister-in-law is a carrier or not. If sister-in-law is a carrier, your nephew has a 50-50 chance of inheriting it but it would have come from grandfather on that side. However... if sister-in-law is also colour-blind then son of two colour-blind parents MUST be colour-blind as there are no good X genes for him to inherit.

Ergates is correct - there are multiple forms and some of them are hereditary but not on the XY chromosome which means the odds are different and males and females are equally likely/unlikely to inherit. But the symptoms are also variable from individual to individual - the faulty gene affects the development of the cones (the colour detectors in the eye) so it's possible for silvercar and sons to all have the same faulty gene but experience it in different ways or it might be a different variant than the classic red/green Daltonism.

Silvertabby

I'm one of the those rare creatures, a colour blind female, presumably because my father and my maternal grandfather were both colour blind, Technically I'm red/green, although I can tell the difference between strong reds and greens - it's shades of brown and green that I have problems with.