Question 2 of 21

What name is given to environmental factors that impact variations in gene expression in identical twins?

... Epigenetic factors include things like diet, exercise and exposure to tobacco smoke.

Question 3 of 21

Which of these sets of siblings are 100 percent identical in terms of genetics?

... Even identical twins don't share identical genomes.

Question 4 of 21

How much of their genetic material do fraternal twins share?

... About half of the genetic material in fraternal twins is shared, which is about the same amount shared by any pair of siblings.

Question 5 of 21

What are the odds that a pregnant woman will give birth to identical triplets?

... The odds of having identical triplets are just 1 in 200 million.

Question 6 of 21

What kind of twins result when more than one egg is fertilized?

... Fraternal twins occur when two separate eggs are fertilized.

Question 7 of 21

How may sets of fraternal twins have two different fathers?

... One out of every 12 sets of fraternal twins has a single mother and two separate biological fathers, which occurs when sperm from two different men fertilize separate eggs around the same time.

Question 8 of 21

Which of these animal species always produces offspring in litters of four identical quadruplets?

... For some unknown reason, armadillos always produce four identical offspring.

Question 9 of 21

Due to differences in their experience while in the womb, even identical twins have their own unique version of this feature.

... Each twin in a pair of identical twins has his or her own unique set of fingerprints.

Question 10 of 21

What are the odds that a pregnant woman will give birth to identical twins?

... About 3 out of every 1,000 births results in a set of identical twins.

Question 11 of 21

Fraternal twins may also be known by this scientific term, which means "coming from multiple eggs."

... Dizygotic twins come from two separate eggs, and thus share only about half of the same genetic material.

Question 12 of 21

Which of these does NOT serve as an explanation for the differences in DNA sequencing within a set of identical twins?

... The genome of identical twins can differ due to gene copy variations or epigenetic (environmental) factors.

Question 13 of 21

Which of these factors increases a woman's odds of having identical twins?

... Scientists have not yet pinpointed any specific factors that increase a woman's odds of giving birth to identical twins.

Question 14 of 21

What would you call a set of triplets in which two of the babies are identical and one is fraternal, or not identical to the other two?

... Polyzygotic triplets occur when two separate eggs are fertilized, and one splits in two, producing one fraternal child and one set of identical twins.

Question 15 of 21

What would you call a set of identical triplets?

... Identical triplets occur when a single fertilized egg splits, then splits again, forming three babies from a single zygote with the same genetic material.

Question 16 of 21

What percentage of twins are identical?

... About one third of all twins are identical, or produced from a single fertilized egg.

Question 17 of 21

While identical twins share the same genetic material, they have different DNA sequences, which are also known as what?

... Contrary to popular belief, even identical twins do not share the same genome.

Question 18 of 21

Which of these factors increases a woman's odds of having fraternal twins?

... Genetics, fertility treatments and even being overweight can all increase a woman's odds of giving birth to fraternal twins.

Question 19 of 21

How much time does it take an egg to split once it's been fertilized, resulting in identical twins?

... No one knows why a zygote chooses to split, but it usually does so two days after fertilization.

Question 20 of 21

What term is used to describe a pair of identical twins?

... Monozygotic refers to a pair of identical twins that come from the same fertilized egg.

Question 21 of 21

What's the largest number of non-identical multiples ever born where every baby lived through the first year?

... There are two recorded cases throughout history where women have given birth to octuplets and all eight babies survived.

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