DNA twins

By Victoria Levin

Scenario

If a pair of twin girls grow up to marry a pair of twin boys, and they both have a child, will their children be twins? Will the cousins be twins?

Answer

Basically No

From meiosis, to punnett squares, to even just plain logical science they all prove that this scenario is completely impossible, even though it would be pretty cool to have a whole line of family be identical.

According to the oxford journal there are 19,000 human genes, so it's almost impossible to have the same genes unless you are actual twins.

When meiosis (cell division after sexual reproduction) occurs it is very unlikely for genes to match unless they are produced with the same people at the same time. Further more, if the cousins were to be somewhat twins age, height, and medical issues would play a big role in changing that.

Meiosis is different from other forms of cell division. Unlike in other forms, the daughter cells in meiosis only have half the number of chromosomes of the parent. This means that the cells produced in meiosis are not exact copies of the original cell. Meiosis is broken down into several stages. Each cell in the process of meiosis involves the cell growing, dividing, splitting, and dividing again in order to produce the four cells at the end of the process. process is one of the more common processes of biology, but it is also the reason why people have some traits over others. According to sciencelearn.org ¨ the passing of genes from one generation to the next is called heredity. Simple organisms pass on genes by duplicating their genetic information and then splitting to form an identical organism. More complex organisms, including humans, produce specialized sex cells (gametes) that carry half of the genetic information, then combine these to form new organisms. The process that produces gametes is called meiosis. Genes are made up of DNA, we share 99.9% of our DNA with other humans, yet our genes are totally different except for twins. Twins are one of the only cases where two beings share the same genes, because once you think about it two people can have brown hair but that brown is never the same shade. Same thing with eyes, ones eyes can be green but never the same shade as someone else. During meiosis in humans, 1 diploid cell (with 46 chromosomes or 23 pairs) undergoes 2 cycles of cell division but only 1 round of DNA replication. The result is 4 haploid daughter cells known as gametes or egg and sperm cells (each with 23 chromosomes – 1 from each pair in the diploid cell).

At conception, an egg cell and a sperm cell combine to form a zygote (46 chromosomes or 23 pairs). This is the 1st cell of a new individual. The halving of the number of chromosomes in gametes ensures that zygotes have the same number of chromosomes from one generation to the next. This is critical for stable sexual reproduction through successive generations.¨

As show below the process of meiosis contains several steps that are unique to every child, except for twins. It is very likely for cousins to receive a similar trait during meiosis, but not every exact trait.

To prove this point a punnett square (a diagram that is used to predict an outcome of a particular cross or breeding experiment.) may be used to show how this is not possible.

This punnett square shows that the father (on top) is heterozygous. His alleles are big G little g. As for the mother (on left), she as well is heterozygous and her alleles are big G little g. The upper case and lower case letters represent the likely hood of receiving as certain trait. Each square is 25% of their child's gene outcome. Twins could be identical or fraternal, so this punnett square could be the same or different for them. As for their offspring's it is even more likely that they will be different.

Even two children from separate births from the same mother are always going to receive different genes, so there would be a less likelihood that the children from separate parents (even though alike) will have the same genes.

After further researching this topic I can confidentially state that in no way can cousins be twins, even if there parents are twins too many medical issues, age issues, and gene issues will prevent any such thing from happening.

Meiosis process

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Punnett square

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