Anyone know the 'science' behind twins?

[AnnieOleTing]

My SIL is expecting twins in November.
We all thought, Oh fab! But, there's no twins in our family, how can this be?

They're in separate sacs, so are assumed to be non-identical.

Then out of the blue, apparently, our Nana's uncles were twins (long dead btw)

Now then,

Rumour has it, twins skip a generation. True or false?

Twins are 'carried by the male Y chromosome', true or false?

Tis all fascinating stuff.
I'd just like to know what anyone knows about the genetic side of things.

Thanks

I believe, but am no expert, that non-identical twins run in families, typcially skipping a generation as you say (well they do in mine).
Think identical twins (same egg, split) are an accident of nature and do not run in families.

i think the twin gene is carried by the female. and it is non identical twins as the woman produces 2 eggs at ovulation. identical twins are not genetic. older woman are also more likely to have twins.

nonidentical twins are two eggs released at ovulation, so that is normally carried by the woman, ie if her mother releases two eggs that there is a chance she will too

Ah that makes more sense, if it is carried on the X, and she produces two eggs.
Thanks girls
Any other thoughts?

gosh i read the title as the science behind twirls

I always thought it was in the mother's family and it skipped a generation (fraternal twins that is). My friend's mother was a twin and then my friend had twins.

twirls are not genetic. curls are though.

that's what I thought too, ghosty, but the db decided it was the male who carried the gene. I think your way is best.

i was told fraternal twins is passed down the female line

they could be identicals, but in separate sacks. thats how my twins were.
non identicals follow the female line because as already said you need two eggs at once.

Moulimoo, that's cool! So they could still be identical? Any idea how that came about?
(as in the biology of it?)

think the seperate sacks thing is how early it splits into two, therefore if it divides very early on the develop own, placentas, sacks etc

Non-id twins run in females of the family....HOWEVER...new research shows that the males in a non-id twin family could pass the twin gene on to their daughters...does that make sense??? e.g...because i have non-id twins, the boys in my family could go on to pass the twin gene to any daughters they may have.

Twin also have to start somewhere and they did with me, there are no twins in my family at all..and i've had 2 sets.

I was told by my G.P that it is a myth about twins skipping a generation too.

How interesting! My nephew's dw had G/B twins (weighing 6lb 4oz and 8lb 5oz )three weeks ago but there's no history of twins on either side of the family, even though the proud mum is one of eight children herself. My nephew already has two singletons.

What are the odds of having two sets of twins, Twinmummyx2, esp with no family history?

Wow Twinmummyx2!! You are top of the tree!

Thanks for all your input, it's so interesting to learn about this.

And to you mums of twins! (And TWO SETS!) Don't know how you do it.

Ahem. I myself have been told I have Irish Twins. Some bloke at work noticed I was pregnant again and told me I must be having Irish twins, as they are close together in age. Officially within 12 months makes them Irish twins. They are in fact 15 months apart.
Didn't know whether to be offended (I am Irish) or laugh. Being Irish I laughed. He's American...

Not quite the same thing though...

I know someone who has 2 sets of identical twin boys. It must be weird to have four sons but only two faces.

It's actually all very complex, and there are almost certainly several genes involved. There's a good recap here if you want all the gory details!

Thanks Tamum! Saves me doing a pubmed search (and will also look good when my boss comes around to have pubmed up instead of MN)

You're welcome It's not actually Pubmed, but NCBI took OMIM under their wing a good few years ago so it looks the same!

lol@ledodgy!

ok.. i read that when you have had a set of non-identical twins there is a 70% chance of having another set if you concieve again within the year of giving birth to twins....each year after the percentage goes down slightly.
So everyone who had had non-identical twins has a high chance of having another multiple pregnancy...scary eh!!!..lol

I have irish twins too then...lol my 3rd and 4th sons have 15mths between them too! And they actually look like twin brothers, not like my actual twin boys who don' look the slightest bit related to each other...lol

Tamum-that link has made my eyes go all funny...lots of big words...lol Very interesting though!

think this all goes to show that twins of all types are really truly special and wonderful to have . I am so proud of my scrummy boys, totally alike in appearance, but two distinct personalities. so well done all you twin mums, and twinmummyx2 hats off to you!!!