Identical female twins marry Identical male twins and have a child each?

Question

Will the children end up looking the same.
In other words:

a1 [identical female 1] + b1 [identical male 1] have a child ab1
a2 [identical female 2] + b2 [identical male 2] have a child ab2

Will the children ab1 and ab2 look identical????

"catt" PLEASE READ THE QUESTION PROPERLY. I DID NOT STATE THAT BROTHERS AND SISTERS WERE MARRYING FOR GOODNESS SAKE!!

Answer 1

Not necessarily, because there is independent assortment of the genes. Thus, if either the males or females are heterozygous for any traits, the gametes they form will be different, and since any sperm can fertilize any egg, there can be random combinations of the traits in each case.

Answer 2

Probably not. Most likely, they will not look the same. However, there is a VERY slim chance of ab1 and ab2 having the same DNA: The chance is approx. 1 in 70 trillion. And that's if you're lucky! More explanation below.

First off, identical twins are a result of a zygote forming then splitting into two babies. Second off, it's only a predisposition to fraternal (non-identical) twins that's inherited, which is inherited through the maternal line (mother's side. Mother's mother's side. etc.). Thirdly, there's the dominance/recessive issue, and sex-linked genes, not to mention incomplete dominance to deal with. And independent assortment.

Dominance/Recessive issue: Let's say that all four people are hetrozygous for the tongue-rolling gene. Rolling is dominant to non-rolling.

That means: Rr x Rr and Rr x Rr


Rr x Rr = RR, Rr, Rr, rr
(One Rr is really rR but the dominant allele is written first due to convention)

So ab1 could be a tongue-roller while ab2 is not.


Sex linked genes: Females are XX, Males are XY (in other words, the father decides the sex of the baby - gender is a social construct)

Sooo....say that both males are colourblind and that both females carry the colourblind allelle. The cross looks like this:
XX' x X'Y and XX' x X'Y

XX' = normal female
X'Y = colourblind male
X'X' = colourblind female
X'Y = colourblind male

And you can see here how the sex can affect what genes are expressed.

Incomplete dominance issue (a heterozygous individual shows an intermediate phenotype):
Let's say that height is controlled by a single gene (it's actually polygenic - controlled by mutiple genes- for simplicity's sake.) and that TT = tall, that Tt, Tt, = medium height (again, one Tt = tT but the domiant allelle is written first due to convention.) and tt = short.

Soo...if all are medium height then:
Tt x Tt and Tt x Tt

Tt x Tt = TT (tall), Tt, Tt, (medium height), tt (short)


And then there's codomiance (both allelles are expressed equally) which shows up in things like blood type.

AO (A blood type individual who carries the recessive O blood type allele) X BO (B blood type individual who carries the recessive O allele.)

AO X BO = AO (A blood type individual who carries the recessive O blood type allele), BO (B blood type individual who carries the recessive O allelle.), AB (AB blood type individual), OO (O blood type individual)

The presence/absence of rhesus blood type protein is a dominance/recessive issue. A positive type individual could have a genotype of ++ or +-. By contrast, an A negative type individual MUST have the -- genotype.

Another point: there's also the issues of chimeras and the fact that the older the parents get when they father the children, the more likely it is that the cells will make a 'mistake' copying themselves into gametes.

Answer 3

No, they will not look identical. Genetic variation occurs in this case. Even if a brother twin marries a sister twin a have several babies, these babies will not look identical. To undertand why, we have to look at the process of meiosis. During Prophase I, the homologue chromosomes pair up and exchange information in a process called "crossing over". This crossing over ensures genetic variation. This exchange of genes is not always the same because chromosomes also differ from each other. Let's suppose both parents have brown eyes with recessive alleles for blue eyes. Sometimes, the crossing over occurs with the allele for brown eyes and, in other occasions, with the allele for blue eyes... and this same process occurs in all the genes we have. So, this is the reason why ab1 can have blue eyes and ab2 can have brown eyes and so with the rest of the characteristics... I hope this explanation is not so confusing but it is hard without a board...

Answer 4

ab1 and ab2 will not be identical as when fertilisation takes place there is random selection of genes
so if they are both heterozygous brown eyes and they have a gene for blue eyes present one child might get blue eyes and the other brown

Answer 5

most likely no, becasue everyone has different DNA...even the identical twins dont have the same DNA...during meiosis the genes are assorted totally different during crossing over and independent assortment and all that other stuff....so the chances of their offspring looking alike are pretty slim.

Answer 6

Depends. If the dominant genes get passed down to all kids then yeah they would look alike. But if dominant went down to one couples kids, and the recessive went to the others, there is a chance they'd look alike but not as much. Just depends on the genes.

Answer 7

Almost certailnly not, after all two children from the same parents don't look the same do they?

Their DNA would match but thats as far as it goes.

Answer 8

they will probably resemble each other but will not be so similar that you couldnt tell them apart. There are millions of possiblities for many traits and it is a certainity that they would have many that were different.

Answer 9

no because during meosis the assortment of genes is totally random, and also due to the law of independent assortment, one set of genes cannot affect the assortment of another set.

Answer 10

first off thats probablly illegal, marrying your sister/brother in-law. most likely they might look identical. 50% chance. The twins DNA would be the same. But it depends who gets the recessive genes.